Reviews - Chem broad -Chem focused - Disinfection - General Treatment - Production - Analysis - Patents -
Catalytic - Other Oxidized forms of Fe - Dissertations


Review Papers on Ferrate
Citation Notes Abstract
Jiang, J.Q. and Lloyd, B. (2002) Progress in the development and use of ferrate(VI) salt as an oxidant and coagulant for water and wastewater treatment. Water Research 36(6), 1397-1408.

very general for water treatment

covers relevant literature through late 90s

This paper reviews the progress in preparing and using ferrate(VI) salt as an oxidant and coagulant for water and wastewater treatment. The literature revealed that due to its unique properties (viz. strong oxidizing potential and simultaneous generation of ferric coagulating species), ferrate(VI) salt can disinfect microorganisms, partially degrade and/or oxidise the organic and inorganic impurities, and remove suspended/colloidal particulate materials in a single dosing and mixing unit process, However, these findings have not yet lead to the full-scale application of ferrate(VI,) in the water industry owing to difficulties associated with the relatively low yield of ferrate(VI), the instability of the chemical depending on its method of preparation, and the lack of adequate studies that have demonstrated its capabilities and advantages over existing water and wastewater treatment methods. Fundamental study is thus required to explore the new preparation methods focusing on increasing the production yield and product's stability and avoiding using hypochlorite or chlorine as the oxidant. Also, the application of ferrate(VI) in drinking water treatment has not been studied systematically and future work in this field is recommended.
Sharma, V.K., Kazama, F., Jiangyong, H. and Ray, A.K. (2005) Ferrates (iron(VI) and iron(V)): environmentally friendly oxidants and disinfectants. Journal of Water and Health 3(1), 45-58.
covers a wide range of water treatment topics Iron(VI) and iron(v), known as ferrates, are powerful oxidants and their reactions with pollutants are typically fast with the formation of non-toxic by-products. Oxidations performed by Fe(VI) and Fe(V) show pH dependence; faster rates are observed at lower pH. Fe(VI) shows excellent disinfectant properties and can inactivate a wide variety of microorganisms at low Fe(VI) doses. Fe(VI) also possesses efficient coagulation properties and enhanced coagulation can also be achieved using Fe(VI) as a preoxidant. The reactivity of Fe(V) with pollutants is approximately 3-5 orders of magnitude faster than that of Fe(VI). Fe(V) can thus be used to oxidize pollutants and inactivate microorganisms that have resistance to Fe(VI). The final product of Fe(VI) and Fe(V) reduction is Fe(III), a non-toxic compound. Moreover, treatments by Fe(VI) do not give any mutagenic/carcinogenic by-products, which make ferrates environmentally friendly ions. This paper reviews the potential role of iron(VI) and iron(V) as oxidants and disinfectants in water and wastewater treatment processes. Examples are given to demonstrate the multifunctional properties of ferrates to purify water and wastewater.
Ghernaout, D., Ghernaout, B. and Naceur, M.W. (2011) Embodying the chemical water treatment in the green chemistry-A review. Desalination 271(1-3), 1-10.   Green chemistry (GC) is the key to sustainable development as it will lead to new solutions to existing problems. Moreover, it will present opportunities for new processes and products and at its heart is scientific and technological innovation. This paper aims to contribute to a better understanding of the new challenges that chemistry is facing. A particular emphasis is accorded to the need for the development of environmentally friendly technologies for water treatment where GC can be satisfied. Indeed, following the establishment of the 12 Principles of GC, there has been a steady growth in our understanding of what GC means. Furthermore, there are great perspectives relating to the greening of chemical water treatment, especially in terms of ferrate(VI) adding, as oxidant/disinfectant/coagulant in the same time, and microchannel reactors which would be considered as promising devices for water treatment due to their proved advantages.

Sharma, V.K. (2007) Disinfection performance of Fe(VI) in water and wastewater: a review. Water Science and Technology 55(1-2), 225-232.

summary of disinfection work (mostly Sharma's) through 2006 Ferrate(VI) [(FeO42-)-O-VI, Fe(VI)] has excellent disinfectant properties and can inactivate a wide variety of microorganisms at low Fe(VI) dosages. The final product of Fe(VI) is Fe(III), a non-toxic Compound. The treatment by Fe(VI) does not give any chlorination by-products, which makes Fe(VI) an environmentally-friendly ion. The results demonstrate that Fe(VI) can inactivate Escherichia coli (E. coli) at lower dosages or shorter contact time than hypochlorite. Fe(VI) can also kill many chlorine resistant organisms, such as aerobic spore-formers and sulphite-reducing clostridia, and would be highly effective in treating emerging toxins in the aquatic environment. Fe(VI) can thus be used as an effective alternate disinfectant for the treatment of water and wastewater. Moreover, Fe(VI) is now becoming economically available in commercial quantities and can be used as a treatment chemical to meet the water demand of this century. This paper reviews the potential role of Fe(VI) as disinfectant in water and wastewater treatment processes.
Sharma, V.K. (2010) Oxidation of nitrogen-containing pollutants by novel ferrate(VI) technology: A review. Journal of Environmental Science and Health Part a-Toxic/Hazardous Substances & Environmental Engineering 45(6), 645-667.
very detailed review of reactions with DON compounds and some PPCPs Nitrogen-containing pollutants have been found in surface waters and industrial wastewaters due to their presence in pesticides, dyes, proteins, and humic substances. Treatment of these compounds by conventional oxidants produces disinfection by-products (DBP). Ferrate(VI) (Fe(VI)O(4)(2), Fe(VI)) is a strong oxidizing agent and produces a non-toxic by-product Fe(III), which acts as a coagulant. Ferrate(VI) is also an efficient disinfectant and can inactivate chlorine resistant microorganisms. A novel ferrate(VI) technology can thus treat a wide range of pollutants and microorganisms in water and wastewater. The aim of this paper is to review the kinetics and products of the oxidation of nitrogen-containing inorganic (ammonia, hydroxylamine, hydrazine, and azide) and organic (amines, amino acids, anilines, sulfonamides, macrolides, and dyes) compounds by ferrate(VI) in order to demonstrate the feasibility of ferrate(VI) treatment of polluted waters of various origins. Several of the compounds can degraded in seconds to minutes by ferrate(VI) with the formation of non-hazardous products. The mechanism of oxidation involves either one-electron or two-electrons processes to yield oxidation products. Future research directions critical for the implementation of the ferrate(VI)-based technology for wastewater and industrial effluents treatment are recommended.
Sharma, V.K. (2011) Oxidation of inorganic contaminants by ferrates (VI, V, and IV)-kinetics and mechanisms: A review. Journal of Environmental Management 92(4), 1051-1073.
stabiliy of ferrate - abs spectra for many Fe species - many rate constants for inorganics Inorganic contaminants are found in water, wastewaters, and industrial effluents and their oxidation using iron based oxidants is of great interest because such oxidants possess multi-functional properties and are environmentally benign. This review makes a critical assessment of the kinetics and mechanisms of oxidation reactions by ferrates (Fe(VI)O(4)(2-), Fe(V)O(4)(3-), and Fe(IV)). The rate constants (k, M(-1) s(-1)) for a series of inorganic compounds by ferrates are correlated with thermodynamic oxidation potentials. Correlations agree with the mechanisms of oxidation involving both one-electron and two-electron transfer processes to yield intermediates and products of the reactions. Case studies are presented which demonstrate that inorganic contaminants can be degraded in seconds to minutes by ferrate(VI) with the formation of non-toxic products.
Yu, X. and Licht, S. (2008) Advances in electrochemical Fe(VI) synthesis and analysis. Journal of Applied Electrochemistry 38(6), 731-742.
both electrochemical synthetic and analytical methods Hexavalent iron species (Fe(VI)) have been known for over a century, and have long-time been investigated as the oxidant for water purification, as the catalysts in organic synthesis and more recently as cathodic charge storage materials. Conventional Fe(VI) syntheses include solution phase oxidation (by hyphchlorite) of Fe(III), and the synthesis of less soluble super-irons by dissolution of FeO(4)(2-), and precipitation with alternate cations. This paper reviews a new electrochemical Fe(VI) synthesis route including both in situ and ex situ syntheses of Fe(VI) salts. The optimized electrolysis conditions for electrochemical Fe(VI) synthesis are summarized. Direct electrochemical synthesis of Fe(VI) compounds has several advantages of shorter synthesis time, simplicity, reduced costs (no chemical oxidant is required) and providing a possible pathway towards more electro-active and thermal stable Fe(VI) compounds. Fe(VI) analytical methodologies summarized in this paper are a range of electrochemical techniques. Fe(VI) compounds have been explored as energy storage cathode materials in both aqueous and non-aqueous phase in "super-iron" battery configurations. In this paper, electrochemical synthesis of reversible Fe(VI/III) thin film towards a rechargeable super-iron cathode is also summarized.
Macova, Z., Bouzek, K., Hives, J., Sharma, V.K., Terryn, R.J. and Baum, J.C. (2009) Research progress in the electrochemical synthesis of ferrate(VI). Electrochimica Acta 54(10), 2673-2683. Sharma's review on electrochemical synthesis There is renewed interest in the +6 oxidation state of iron, ferrate (VI) (Fe(VI)O(4)(2-)), because of its potential as a benign oxidant for organic synthesis, as a chemical in developing cleaner ("greener") technology for remediation processes. and as an alternative for environment-friendly battery cathodes. This interest has led many researchers to focus their attention on the synthesis of ferrate(VI). Of the three synthesis methods, electrochemical, wet chemical and thermal, electrochemical synthesis has received the most attention due to its ease and the high purity of the product. Moreover, electrochemical processes use an electron as a so-called clean chemical. thus avoiding the use of any harmful chemicals to oxidize iron to the +6 oxidation state. This paper reviews the development of electrochemical methods to synthesize ferrate(VI). The approaches chosen by different laboratories to overcome some of the difficulties associated with the electrochemical synthesis of ferrate(VI) are summarized. Special attention is paid to parameters such as temperature, anolyte, and anode material composition. Spectroscopic work to understand the mechanism of ferrate(VI) synthesis is included. Recent advances in two new approaches, the use of an inert electrode and molten hydroxide salts, in the synthesis of ferrate(VI) are also reviewed. Progress made in the commercialization of ferrate(VI) continuous production is briefly discussed as well.
Licht, S., Wang, B.H. and Ghosh, S. (1999) Energetic iron(VI) chemistry: The super-iron battery. Science 285(5430), 1039-1042.
Science article - pertains to use in batteries, not water treatment Higher capacity batteries based on an unusual stabilized iron(VI) chemistry are presented. The storage capacities of alkaline and metal hydride batteries are largely cathode limited, and both use a potassium hydroxide electrolyte. The new batteries are compatible with the alkaline and metal hydride battery anodes but have higher cathode capacity and are based on available, benign materials. Iron(VI/III) cathodes can use low-solubility K2FeO4 and BaFeO4 salts with respective capacities of 406 and 313 milliampere-hours per gram. Super-iron batteries have a 50 percent energy advantage compared to conventional alkaline batteries. A cell with an iron(VI) cathode and a metal hydride anode is significantly (75 percent) rechargeable.


Papers on Ferrate Chemistry: Broad Scope
Citation Notes Abstract
Sharma, V. K. (2013). "Ferrate(VI) and ferrate(V) oxidation of organic compounds: Kinetics and mechanism." Coordination Chemistry Reviews 257(2): 495-510.
Review of Organic Rates and mechanisms This review presents a critical assessment of the kinetics and mechanisms of the oxidation of organic compounds, X (organosulfur compounds, amines, phenols, alcohols, hydrocarbons, ascorbate, and pharmaceuticals) by ferrate(VI) ((FeO42-)-O-VI) and ferrate(V) ((FeO43-)-O-V). The rate constants (k(app). M-1 s(-1)) of reactions of these compounds with ferrate(VI) and ferrate(V) usually decrease with increase in pH in alkaline media and the species-specific rate constants were evaluated from pH-dependent kinetics. The rate constants for the reactions of (HFeO4-)-O-VI and (HFeO42-)-O-V with X were correlated with 1 - e(-) and 2 - e(-) reduction potentials in order to understand the mechanisms of the reactions. Ferrate(V) generally oxidizes compounds by a 2 - e(-) transfer step. The reactions of ferrate(VI) with compounds may be characterized most commonly by (i) a 1 - e(-) transfer step from Fe(VI) to Fe(V), followed by a 2 e- transfer to Fe(111) as the reduced product (Fe-VI -> Fe-V -> Fe-III), and (ii) 2 - e(-) transfer steps (Fe-VI -> Fe-IV -> Fe-II). Oxygen-atom transfer to the compounds may occur through involvement of either ferrate(VI) or ferrate(V) in the oxidations carried out by ferrate(VI). Hammett-type relationships of reactions provided additional information on intermediates involved in oxidation processes and proposed mechanisms are consistent with the oxidized products of the reactions. Oxidation of biological species by ferrate(VI) is also briefly presented
Lee, Y. and von Gunten, U. (2010) Oxidative transformation of micropollutants during municipal wastewater treatment: Comparison of kinetic aspects of selective (chlorine, chlorine dioxide, ferrate(VI), and ozone) and non-selective oxidants (hydroxyl radical). Water Research 44(2), 555-566.

best review of kinetic data with comparison to other oxidants

considers oxidant lifetime & exposure giving doses for micropollutant removal

Chemical oxidation processes have been widely applied to water treatment and may serve as a tool to minimize the release of micropollutants (e g pharmaceuticals and endocrine disruptors) from municipal wastewater effluents into the aquatic environment The potential of several oxidants for the transformation of selected micropollutants such as atenolol, carbamazepine, 17 alpha-ethinylestradiol (EE2), ibuprofen, and sulfamethoxazole was assessed and compared The oxidants include chlorine, chlorine dioxide, ferrate(VI), and ozone as selective oxidants versus hydroxyl radicals as non-selective oxidant. Second-order rate constants (k) for the reaction of each oxidant show that the selective oxidants react only with some electron-rich organic moieties (ERMs), such as phenols, anilines, olefins, and deprotonated-amines in contrast, hydroxyl radicals show a nearly diffusion-controlled reactivity with almost all organic moieties (k > 10(9) M-1 s(-1)) Due to a competition for oxidants between a target micropollutant and wastewater matrix (i e effluent organic matter, EfOM), a higher reaction rate with a target micropollutant does not necessarily translate into more efficient transformation For example, transformation efficiencies of EE2, a phenolic micropollutant, in a selected wastewater effluent at pH 8 varied only within a factor of 7 among the selective oxidants, even though the corresponding k for the reaction of each selective oxidant with EE2 varied over four orders of magnitude in addition, for the selective oxidants, the competition disappears rapidly after the ERMs present in EfOM are consumed In contrast, for hydroxyl radicals, the competition remains practically the same during the entire oxidation Therefore, for a given oxidant dose, the selective oxidants were more efficient than hydroxyl radicals for transforming ERMs-containing micropollutants, while hydroxyl radicals are capable of transforming micropollutants even without ERMs Besides EfOM, ammonia, nitrite, and bromide were found to affect the micropollutant transformation efficiency during chlorine or ozone treatment.
Sharma, V.K. (2010) Oxidation of Inorganic Compounds by Ferrate(VI) and Ferrate(V): One-Electron and Two-Electron Transfer Steps. Environmental Science & Technology 44(13), 5148-5152.

most complete set of rate data for inorganics

mostly a lit review

Ferrate(VI) (Fe(VI)O(4)(-), Fe(VI)) and ferrate(V) (Fe(V)O(4)(3-), Fe(V)) have a high oxidizing power and upon decomposition form a nontoxic byproduct Fe(III), which makes them environmentally friendly oxidants in water and wastewater treatment The kinetics of the reaction between Fe(VI) and I(-) was determined using a stopped-flow technique. The second-order rate constants (k, M(-1) s(-1)) for the oxidation of I- and other inorganic compounds by protonated ferrate(VI)(HFe(VI)O(4)(-)) and ferrate(V) (Fe(V)O(4)(3-)) ions were correlated with thermodynamic reduction potentials to understand the reaction mechanisms. A linear relationship was found between log k and 1-e(-) reduction potentials for iodide, cyanides, and superoxide while oxy-compounds of nitrogen, sulfur, selenium, and arsenic demonstrated a linear relationship for 2-e(-) reduction potentials. The estimated limits for the reduction potentials of the couple are E(0)(Fe(VI)/Fe(V)) >= 0.76 V and E(0)(Fe(VI)/Fe(IV)) >= -0.18 V. Conclusions drawn from the correlations are consistent with the mechanisms postulated from stoichiometries, intermediates, and products of the reactions. Implication of the kinetic results in treatment using ferrate(VI) is briefly discussed.
Johnson Michael, D., J. Hornstein Brooks, and J. Wischnewsky. 2008. Ferrate(VI) Oxidation of Nitrogenous Compounds, p. 177-188, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. hydrazines, hydroxylamines, azo compounds, analines The oxidation kinetics of a series of nitrogen containing compounds by ferrate(VI), FeO42-, is described. Each of these reactions was studied at 25°C using spectrophotometric techniques. These included stopped-flow, rapid scanning spectrophotometry and convention Diode array spectrophotometry. Mechanistic schemes are proposed for each system studied along with potential intermediates when observed or required by kinetic data.
Carr James, D. 2008. Kinetics and Product Identification of Oxidation by Ferrate(VI) of Water and Aqueous Nitrogen Containing Solutes, p. 189-196, In V. K. Sharma, ed. Ferrates, ACS Symp. 985.

Fe(VI) decomposition

inorganic-N and amines

Water is shown to be oxidized by ferrate(VI) via a pathway dominated by protonated ferrate and leading to molecular oxygen via hydrogen peroxide. Nitrogen-containing solutes are oxidized in competition with water oxidation. Products of oxidation are determined by a variety of analytical methods. Iron(II) is shown to be an intermediate state of iron which originated as Fe(VI) but Fe(III) is the final product in the absence of a trapping reagent for Fe(II). Nitroxyl is shown to be an important intermediate species in the oxidation of azide and hydroxylamine.
Lee, Y., Yoon, J. and Von Gunten, U. (2005) Kinetics of the oxidation of phenols and phenolic endocrine disruptors during water treatment with ferrate (Fe(VI)). Environmental Science & Technology 39(22), 8978-8984.

estrogens & phenols - good kinetic analysis


The ability of ferrate (Fe(Vl)) to oxidize phenolic endocrine-disrupting chemicals (EDCs) and phenols during water treatment was examined by determining the apparent second-order rate constants (k(app)) for the reaction of Fe(VI) with selected environmentally relevant phenolic EDCs(17 alpha-ethinylestradiol, beta-estradiol, and bisphenol A) and 10 substituted phenols at pH values ranging from 6 to 11. The three selected groups of EDCs showed appreciable reactivity with Fe(VI) (k(app) at pH 7 ranged from 6.4 x 10(2) to 7.7 x 10(2) M-1 s(-1)). The kapp for the substituted phenols studied at pH 7 ranged from 6.6 to 3.6 x 10(3) M-1 s(-1), indicating that many other potential phenolic ENS can be oxidized by Fe(VI) during water treatment. The Hammett-type correlations were determined for the reaction between HFeO4- and the undissociated (log(k) = 2.24-2.27 sigma(+)) and dissociated phenol (log(k) = 4.33-3.60 sigma(+)). A comparison of the Hammett correlation obtained for the reaction between HFeO4- and dissociated phenol with those obtained from other drinking water oxidants revealed that HFeO4- is a relatively mild oxidant of phenolic compounds. The effectiveness of Fe(VI) for the oxidative removal of phenolic EDCs was also confirmed in both natural water and wastewater.
Sharma, V.K., Li, X.Z., Graham, N. and Doong, R.A. (2008) Ferrate(VI) oxidation of endocrine disruptors and antimicrobials in water. Journal of Water Supply Research and Technology-Aqua 57(6), 419-426.
estrogens, sulfas, and BPA, including BPA degradation pathways Potassium ferrate(VI) (K2FeO4) has advantageous properties such as a dual function as an oxidant and disinfectant with a non-toxic byproduct, iron(III), which makes it an environmentally friendly chemical for water treatment. This paper presents an assessment of the potential of ferrate(VI) to oxidize representative endocrine disruptors (EDs) and antimicrobials during water treatment using information about reaction kinetics and products. Selected EDs were bisphenol A (BPA) and 17 alpha-ethynylestradiol (EE2), estrone (E1), 17 beta-estradiol (E2), and estriol (E3), and sulfonamides and tetracycline were representative pharamaceuticals. The second-order rate constants, k, of the oxidation reactions at neutral pH were in the range from 6.50-11.8 x 10(2) M(-1)s(-1) and 0.79-15.0 x 10(2) M(-1)s(-1) for EDs and sulfonamides, respectively. At a 10 mgL(-1) K2FeO4 dose, half-lives of the oxidation reaction would be in seconds at a neutral pH. The values of k, and the reaction half-lives, varied with pH. Oxidation products from the reaction with BPA and sulamethoxazole (SMX) at molar ratios of similar to 5:1 were found to be relatively less toxic. Overall, ferrate(VI) oxidation could be an effective treatment method for the purification of waters containing these particular EDs and antimicrobials.
Lee, C., Lee, Y., Schmidt, C., Yoon, J. and Von Gunten, U. (2008) Oxidation of suspected N-nitrosodimethylamine (NDMA) precursors by ferrate (VI): Kinetics and effect on the NDMA formation potential of natural waters. Water Research 42(1-2), 433-441.

kinetic study of dimethylamine compounds as NDMA precursors

ferrate destroys most of these but is less effective for NDMA-FP in river water

The potential of ferrate (Fe(VI)) oxidation to remove N-nitrosodimethylamine (NDMA) precursors during water treatment was assessed. Apparent second-order rate constants (k(app)) for the reactions of NDMA and its suspected precursors (dimethylamine (DMA) and 7 tertiary amines with DMA functional group) with Fe(VI) were determined in the range of pH 6-12. Four model NDMA precursors (dimethyldithiocarbamate, dimethylaminobenzene, 3-(dimethylaminomethyl)indole and 4-dimethylaminoantipyrine) showed high reactivity toward Fe(VI) with k(app) values at pH 7 between 2.6 x 10(2) and 3.2 x 10(5) M-1 s(-1). The other NDMA precursors (DMA, trimethylamine, dimethylethanolamine, dimethylformamide) and NDMA had kapp values ranging from 0.55 to 9.1 M-1 s(-1) at pH 7. In the second part of the study, the NDMA formation potentials (NDMA-FP) of the model NDMA precursors and natural waters were measured with and without pre-oxidation by Fe(VI). For most of the NDMA precursors with the exception of DMA, a significant reduction of the NDMA-FP (>95%) was observed after complete transformation of the NDMA precursor. This result was supported by low yields of DMA from the Fe(VI) oxidation of tertiary amine NDMA precursors. Pre-oxidation of several natural waters (rivers Rhine, Neckar and Pfinz) with a high dose of Fe(VI) (0.38 mM = 21 mg L-1 as Fe) led to removals of the NDMA-FP of 46-84%. This indicates that the NDMA precursors in these waters have a low reactivity toward Fe(VI) because it has been shown that for fast-reacting NDMA precursors Fe(VI) doses of 20 mu M (1.1 mg L-1 as Fe) are sufficient to completely oxidize the precursors.




Papers on Ferrate Chemistry: Focused
Citation Notes Abstract
Sharma, V. K., F. Liu, et al. (2013). "Oxidation of beta-lactam antibiotics by ferrate(VI)." Chemical Engineering Journal 221: 446-451.
antibiotics Amoxicillin(AMX) and ampicillin (AMP), penicillin class p-lactam antibiotics, have been detected in wastewater effluents and their release into the environment may involve long-term risks such as toxicity to aquatic organisms and endocrine disruption in higher organisms. This paper demonstrates the removal of AMX and AMP by ferrate(VI) (Fe(VI)) by performing kinetics and stoichiometric experiments. The dependence of the second-order rate constants of the reaction between Fe(VI) and AMX (or AMP) on pH was explained using acid-base equilibria of Fe(VI) and organic molecules. The kinetics study with the model compound, 6-aminopencillanic acid and the pH dependence behavior suggested that Fe(VI) reacted with the amine moieties of the studied beta-lactams. The reactivity of different oxidants with AMX have been shown to follow the sequence:.(OH)-O-center dot approximate to SO4 center dot- > bromine > ozone > chlorine > Fe(VI). The required molar stoichiometric ratios ([Fe(VI)]:[beta-lactam]) for the complete removal of AMX and AMP by Fe(VI) were about 4.5 and 3.5, respectively. The Fe(VI) is able to eliminate AMX and AMP and hence is likely to also oxidize other p-lactams effectively.
Casbeer, E. M., V. K. Sharma, et al. (2013). "Kinetics and Mechanism of Oxidation of Tryptophan by Ferrate(VI)." Environmental Science & Technology 47(9): 4572-4580.
Tryptophan Kinetics of the oxidation of tryptophan (Trp) and kynurenine (Kyn), precursors of nitrogenous disinfection byproducts (N-DBP), by ferrate(VI) ((FeO42-)-O-VI Fe(VI)) were investigated over the acidic to basic pH range. The second-order rate constants decreased with increase in pH, which could be described by the speciation of Fe(VI) and Trp (or Kyn). The trend of pH dependence of rates for Trp (i.e., aromatic alpha-amino acid) differs from that for glycine (i.e., aliphatic alpha-amino acid). A nonlinear relationship between transformation of Trp and the added amount of Fe(VI) was found. This suggests that the formed intermediate oxidized products (OPs), identified by LC-PDA and LC-MS techniques, could possibly compete with Tip to react with Fe(VI). N-Formylkynurenine (NFK) at pH 7.0 and 4-hydroxyquinoline (4-OH Q) and kynurenic acid (Kyn-A) at pH 9.0 were the major OPs. Tryptophan radical formation during the reaction was confirmed by the rapid-freeze quench EPR experiments. The oxygen atom transfer from Fe(VI) to NFK was demonstrated by reacting (FeO42-)-O-18 ion with Tip. A proposed mechanism explains the identified OPs at both neutral and alkaline pH. Kinetics and OPs by Fe(VI) were compared with other oxidants (chlorine, ClO2 center dot, O-3, and (OH)-O-center dot).
Anquandah, G. A. K., V. K. Sharma, et al. (2013). "Ferrate(VI) oxidation of propranolol: Kinetics and products." Chemosphere 91(1): 105-109.
Propranolol The oxidation of propranolol (PPL), a beta-blocker by ferrate(VI) (Fe(VI)) was studied by performing kinetics, stoichiometry, and analysis of the reaction products. The rate law for the oxidation of PPL by Fe(VI) was first-order with respect to each reactant. The dependence of second-order rate constants of the reaction of Fe(VI) and PPL on pH was explained using acid-base equilibrium of Fe(VI) and PPL. The required molar stoichiometry for the complete removal of PPL was determined to be 6:1 ([Fe(VI):[PPL]). The identified products using liquid chromatography-tandem mass spectrometry were oxidized product (OP)-292, OP-308, and OP-282. The formed OPs could possibly compete with the parent molecule to react with Fe(VI) and thus resulted in a non-linear relationship between degradation of PPL and the added amount of Fe(VI). Rate and removal studies indicate the Fe(VI) is able to oxidize PPL and hence can also oxidize other beta-blockers, e.g., atenolol and metoprolol.
Sharma, V. K., K. Siskova, et al. (2012). Mechanism of Oxidation of Cysteine and Methionine by Ferrate(VI): Mossbauer Investigation. Mossbauer Spectroscopy in Materials Science - 2012. J. Tucek and L. Machala. 1489: 139-144.
Cysteine & Methionine Oxidation of organosulfur compounds (S) by ferrate(VI) ((FeO42-)-O-VI, Fe(VI)) proceeds by the transfer of oxygen atom to S. A vast amount of literature proposed oxygen atom transfer (OAT) via 2-e(-) transfer process in which Fe(IV) acts as an intermediate, and Fe(II) was also proposed to be an intermediate or final reduced iron species of Fe(VI) (Fe-VI -> Fe-IV -> Fe-II). In this paper, Mossbauer spectroscopy was applied to explore intermediate iron species in the oxidation of cysteine (Cys) and methionine (Met) by Fe(VI). In the oxidation of Cys, both Fe(II) and Fe(III) were observed while only Fe(III) was seen in the oxidation of Met by Fe(VI). These results support that no Fe(II) species was formed in the oxidation of Met before forming Fe(III). These results are in consistency with the possibility of initial 1-e(-) transfer with the formation of Fe(V) species and subsequent 2-e(-) transfer to yield Fe(III) (Fe-VI -> Fe-V -> Fe-III).
Yang, B., Ying, G.G., Zhao, J.L., Liu, S., Zhou, L.J. and Chen, F. (2012) Removal of selected endocrine disrupting chemicals (EDCs) and pharmaceuticals and personal care products (PPCPs) during ferrate(VI) treatment of secondary wastewater effluents. Water Research 46(7), 2194-2204.

many PPCPs

% removals, no kinetics

We investigated the removal efficiencies of 68 selected endocrine disrupting chemicals (EDCs) and pharmaceuticals and personal care products (PPCPs) spiked in a wastewater matrix by ferrate (Fe(VI)) and further evaluated the degradation of these micropollutants present in secondary effluents of two wastewater treatment plants (WWTPs) by applying Fe(VI) treatment technology. Fe(VI)treatment resulted in selective oxidation of electron-rich organic moieties of these target compounds, such as phenol, olefin, amine and aniline moieties. But Fe(VI) failed to react with triclocarban, 3 androgens, 7 acidic pharmaceuticals, 2 neutral pharmaceuticals and erythromycin-H2O.Thirty-one target EDCs and PPCPs were detected in the effluents of the two WWTPs with concentrations ranging from 0.2 +/- 0.1 ng L-1 to 1156 +/- 182 ng L-1.Fe(VI) treatment resulted in further elimination of the detected EDCs and PPCPs during Fe(VI) treatment of the secondary wastewater effluents. The results from this study clearly demonstrated the effectiveness of Fe(VI) treatment as a tertiary treatment technology for a broad spectrum of micropollutants in wastewater
Jiang, J.Q., Zhou, Z.W. and Pahl, O. (2012) Preliminary study of ciprofloxacin (cip) removal by potassium ferrate(VI). Separation and Purification Technology 88, 95-98. Ciprofloxacin Ciprofloxacin was identified among the top 10 of high priority pharmaceuticals detected in aquatic environment. Potassium ferrate(VI) is a strong oxidant which possesses very high redox potential and has been widely studied in water disinfection and removing organic and inorganic pollutants. There has been one published work to detail the removal of phosphorus as well as micro-pollutants including ciprofloxacin by ferrate in wastewater treatment. However, developing a simple ciprofloxacin detection method and study of feasibility of its treatment by ferrate was the objective of this work. Solid phase extraction (SPE) and UV/vis spectrophotometer at 280 nm was employed to analyse CIP. A series of jar test experiments was carried out to evaluate the ferrate performance for CIP reduction. Results demonstrated that a SPE coupled with simple UV/vis spectrophotometric method can detect CIP with detection limit of 10 mu g/L for model wastewater samples. Ferrate can remove at least 60% of CIP from model wastewater even at very low ferrate doses (<0.3 mg/L). Besides, with increasing in ferrate dose up to 1 mg/L as Fe, the removal efficiency of CIP was higher than 80%. However, increasing ferrate dose further did not show significant increasing in CIP removal. Initial pH of CIP model wastewater samples has no obvious influence on CIP removal, while final solution pH (adjusted and after dosing ferrate) affected the performance of ferrate treatment significantly. CIP removal efficiency by ferrate decreased significantly if final pH of the waste water solution was greater than CIP's pK(a) (i.e. pH > 8)
Sharma, V.K., Sohn, M., Anquandah, G.A.K. and Nesnas, N. (2012) Kinetics of the oxidation of sucralose and related carbohydrates by ferrate(VI). Chemosphere 87(6), 644-648.

Sucralose & other sugars

vs pH

The kinetics of the oxidation of sucralose, an emerging contaminant, and related monosaccharides and disaccharides by ferrate(VI) (Fe(VI)) were studied as a function of pH (6.5-10.1) at 25 degrees C. Reducing sugars (glucose, fructose, and maltose) reacted faster with Fe(VI) than did the non-reducing sugar sucrose or its chlorinated derivative, sucralose. Second-order rate constants of the reactions of Fe(VI) with sucralose and disaccharides decreased with an increase in pH. The pH dependence was modeled by considering the reactivity of species of Fe(VI), (HFeO4- and FeO42-) with the studied substrates. Second-order rate constants for the reaction of Fe(VI) with monosaccharides displayed an unusual variation with pH and were explained by considering the involvement of hydroxide in catalyzing the ring opening of the cyclic form of the carbohydrate at increased pH. The rate constants for the reactions of carbohydrates with Fe(VI) were compared with those for other oxidant species used in water treatment and were briefly discussed.
Zimmermann, S.G., Schmukat, A., Schulz, M., Benner, J., von Gunten, U. and Ternes, T.A. (2012) Kinetic and Mechanistic Investigations of the Oxidation of Tramadol by Ferrate and Ozone. Environmental Science & Technology 46(2), 876-884.
The kinetics and oxidation products (OPs) of tramadol (TRA), an opioid, were investigated for its oxidation with ferrate (Fe(VI)) and ozone (O-3). The kinetics could be explained by the speciation of the tertiary amine moiety of TRA, with apparent second-order rate constants of 7.4 (+/- 04) M-1 s(-1) (Fe(VI)) and 4.2 (+/- 0.3) x 10(4) M-1 s(-1) (O-3) at pH 8.0, respectively. In total, six OPs of TRA were identified for both oxidants using Qq-LIT-MS, LTQFT-MS, GC-MS, and moiety-specific chemical reactions. In excess of oxidants, these OPs can be further transformed to unidentified OPs. Kinetics and OP identification confirmed that the lone electron pair of the amine-N is the predominant site of oxidant attack. An oxygen transfer mechanism can explain the formation of N-oxide-TRA, while a one-electron transfer may result in the formation of N-centered radical cation intermediates, which could lead to the observed N-dealkylation, and to the identified formamide and aldehyde derivatives via several intermediate steps. The proposed radical intermediate mechanism is favored for Fe(VI) leading predominantly to N-desmethyl-TRA (ca. 40%), whereas the proposed oxygen transfer prevails for O-3 attack resulting in N-oxide-TRA as the main OP (ca. 90%).
Yang, B., Ying, G.G., Zhang, L.J., Zhou, L.J., Liu, S. and Fang, Y.X. (2011) Kinetics modeling and reaction mechanism of ferrate(VI) oxidation of benzotriazoles. Water Research 45(6), 2261-2269.

benzotriazoles (5)


kinetics vs pH, with LFERs

Benzotriazoles (BTs) are high production volume chemicals with broad application in various industrial processes and in households, and have been found to be omnipresent in aquatic environments. We investigated oxidation of five benzotriazoles (BT: 1H-benzotriazole; 5MBT: 5-methyl-1H-benzotriazole; DMBT: 5,6-dimethyl-1H-benzotriazole hydrate; 5CBT: 5-chloro-1H-benzotriazole; HBT: 1-hydroxybenzotriazole) by aqueous ferrate (Fe(VI)) to determine reaction kinetics as a function of pH (6.0-10.0), and interpreted the reaction mechanism of Fe(VI) with BTs by using a linear free-energy relationship. The pK(a) values of BT and DMBT were also determined using UV-Visible spectroscopic method in order to calculate the species-specific rate constants, and they were 8.37 +/- 0.01 and 8.98 +/- 0.08 respectively. Each of BTs reacted moderately with Fe(VI) with the k(app) ranged from 7.2 to 103.8 M(-1)s(-1) at pH 7.0 and 24 +/- 1 degrees C. When the molar ratio of Fe(VI) and BTs increased up to 30:1, the removal rate of BTs reached about >95% in buffered milli-Q water or secondary wastewater effluent. The electrophilic oxidation mechanism of the above reaction was illustrated by using a linear free-energy relationship between pH-dependence of species-specific rate constants and substituent effects (sigma p). Fe(VI) reacts initially with BTs by electrophilic attack at the 1,2,3-triazole moiety of BT, 5MBT, DMBT and 5CBT, and at the N-OH bond of HBT. Moreover, for BT, 5MBT, DMBT and 5CBT, the reactions with the species HFeO(4)(-) predominantly controled the reaction rates. For HBT, the species H(2)FeO(4) with dissociated HBT played a major role in the reaction. The results showed that Fe(VI) has the ability to degrade benzotriazoles in water.
Remsberg Jarrett, R., P. Rice Clifford, H. Kim, O. Arikan, and C. Moon. 2008. Removal of Estrogenic Compounds in Dairy Waste Lagoons by Ferrate(VI), p. 420-433, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. BPA & Hormones Ferrate(VI) was used to remove steroidal estrogens (SE) from dairy waste lagoon effluent (DWLE). Dairy lagoon sites were sampled for estrogenic content (EC) and assayed using high performance liquid chromatography coupled to triple quadrupole mass spectrometry. Effects of varying amounts of ferrate(VI) and ferric chloride treatments on the EC of these DWLE samples were determined. Of the compounds measured, 17?-estradiol, 19.7 µg/L, was the most abundant and estriol, 2.10 µg/L the least abundant. When DWLE was treated with a high concentration (0.84%) of ferrate(VI) there was a significant decrease (>50%) in 17?-estradiol content. Ferrate(VI) treatment of DWLE may be an environmentally sound approach to reduce estrogenic compounds.
Zhang, P.Y., Zhang, G.M., Dong, J.H., Fan, M.H. and Zeng, G.M. (2012) Bisphenol A oxidative removal by ferrate (Fe(VI)) under a weak acidic condition. Separation and Purification Technology 84, 46-51.
Bisphenol A
Recently there has been increasing concerns on widespread occurrence of endocrine disrupting chemicals (EDCs) in aquatic environment. Bisphenol A (BPA) in water was oxidized as a target EDC by K2FeO4 (Fe(VI)) in this study. The results showed that BPA was effectively removed within a broad initial water pH range of 5.0-9.5, especially under a weak acidic condition between the initial pH 5 and 6. When the initial BPA concentration was about 1.5 mg L-1, BPA could be completely removed with a oxidation time of 30 min and a Fe(VI)/BPA molar ratio of 3.0. After Fe(VI) oxidation, UV254 of the water samples significantly increased, indicating that BPA degradation intermediates and end products still contained phenyl ring. Further online UV scanning showed that the UV absorbance obviously changed within the UV range of 190-215 nm and 230-300 nm during Fe(VI) oxidation. The DOC of water samples reduced with the increase of Fe(VI) dosage and prolonging of oxidation time, and about 50% of BPA was mineralized after Fe(VI) oxidation under a Fe(VI)/BPA molar ratio of 4.0. The influences of coexisting constituents such as humic acids, SiO32-, HCO3- and tert-butanol were studied. The results showed that humic acids and SiO32- notably inhibited the BPA removal; tert-butanol slightly decreased the BPA removal: and the existence of HCO3- slightly enhanced the BPA removal.
Anquandah, G.A.K., Sharma, V.K., Knight, D.A., Batchu, S.R. and Gardinali, P.R. (2011) Oxidation of Trimethoprim by Ferrate(VI): Kinetics, Products, and Antibacterial Activity. Environmental Science & Technology 45(24), 10575-10581.
Kinetics, stoichiometry, and products of the oxidation of trimethoprim (TMP), one of the most commonly detected antibacterial agents in surface waters and municipal wastewaters, by ferrate(VI) (Fe(VI)) were determined. The pH dependent second-order rate constants of the reactions of Fe(VI) with TMP were examined using acid-base properties of Fe(VI) and TMP. The kinetics of reactions of diaminopyrimidine (DAP) and trimethoxytoluene (TMT) with Fe(VI) were also determined to understand the reactivity of Fe(VI) with TMP. Oxidation products of the reactions of Fe(VI) with TMP and DAP were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Reaction pathways of oxidation of TMP by Fe(VI) are proposed to demonstrate the cleavage of the TMP molecule to ultimately result in 3,4,5,-trimethoxybenzaldehyde and 2,4-dinitropyrimidine as among the final identified products. The oxidized products mixture exhibited no antibacterial activity against E. coli after complete consumption of TMP. Removal of TMP in the secondary effluent by Fe(VI) was achieved.
Yang, B., Ying, G.G., Zhao, J.L., Zhang, L.J., Fang, Y.X. and Nghiem, L.D. (2011) Oxidation of triclosan by ferrate: Reaction kinetics, products identification and toxicity evaluation. Journal of Hazardous Materials 186(1), 227-235.


kinetic study - includes impacts on toxicity and MS identification of intermediates

The oxidation of triclosan by commercial grade aqueous ferrate (Fe(VI)) was investigated and the reaction kinetics as a function of pH (7.0-10.0) were experimentally determined. Intermediate products of the oxidation process were characterized using both GC-MS and RRLC-MS/MS techniques. Changes in toxicity during the oxidation process of triclosan using Fe(VI) were investigated using Pseudokirchneriella subcapitata growth inhibition tests. The results show that triclosan reacted rapidly with Fe(VI), with the apparent second-order rate constant. k(app), being 754.7 M(-1) s(-1) at pH 7. At a stoichiometric ratio of 10:1 (Fe(VI):triclosan), complete removal of triclosan was achieved. Species-specific rate constants, It, were determined for reaction of Fe(VI) with both the protonated and deprotonated triclosan species. The value of k determined for neutral triclosan was 6.7(+/- 1.9) x 10(2) M(-1) s(-1), while that measured for anionic triclosan was 7.6(+/- 0.6) x 10(3) M(-1) s(-1). The proposed mechanism for the oxidation of triclosan by the Fe(VI) involves the scission of ether bond and phenoxy radical addition reaction. Coupling reaction may also occur during Fe(VI) degradation of triclosan. Overall, the degradation processes of triclosan resulted in a significant decrease in algal toxicity. The toxicity tests showed that Fe(VI) itself dosed in the reaction did not inhibit green algae growth.
Yang, S.-f., and R.-a. Doong. 2008. Preparation of Potassium Ferrate for the Degradation of Tetracycline, p. 404-419, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. Tetracycline Tetracycline antibiotics are widely used in veterinary medicine and growth-promoting antibiotics for treatment and/or prevention of infectious disease because of their broad-spectrum activity and cost benefit. Tetracycline is rather persistent and a large fraction, which can be up to 75 %, of a single dose can be excreted in non-metabolized form in manures. In addition, potassium ferrate (Fe(VI)) is a powerful oxidant over a wide pH range and can be used as an environmentally friendly chemical in treated and natural waters. Therefore, the ability of ferrate (VI) to oxidize tetracycline in aqueous solution was examined in this study. The stability of Fe(VI) was monitored by the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) method. Results showed that the decomposition of Fe(VI) is highly dependent on pHs. A minimum decomposition rate constant of 1 x 10-4 s-1 was observed at pH 9.2. A stoichiometry of 1.4:1 was observed for the reaction of tetracycline with Fe(VI) at pH 9.2. In addition, tetracycline was rapidly transformed in the presence of low concentrations of Fe(VI) in the pH rang 8.3-10.0. The degradation efficiency of tetracycline is affected by both pH and initial Fe(VI) concentration. The degradation of tetracycline by Fe(VI) was also confirmed by ESI-MS and total organic carbon (TOC) analyses.
de Luca, S.J., Pegorer, M.G. and de Luca, M.A. (2010) Aqueous oxidation of microcystin-LR by ferrate(VI). Engenharia Sanitaria E Ambiental 15(1), 5-10.


in Portuguese

Algae toxins are becoming a severe problem in the water treatment industry, especially for human and animal consumption. Traditional treatment processes have failed in complying with water supply standards. Potassium ferrate(VI) is a powerful oxidant, disinfectant and, also, a coagulant. In this paper, the results of microcystin-LR oxidation by ferrate(VI) ion are presented. Kinetic and jar tests showed a average value of 0,012 min(-1) for the pseudo first order reaction rate constant, for 100 and 200 mu g.L(-1) concentration of MC-LR. Ferrate(VI) dosages between 1.6 and 5.0 mg.L(-1) suggest that water supply standards for MC-LR can be reached, which means that the oxidant may be employed as coadjuvant in water treatment.
Hu, L., Martin, H.M., Arcs-Bulted, O., Sugihara, M.N., Keatlng, K.A. and Strathmann, T.J. (2009) Oxidation of Carbamazepine by Mn(VII) and Fe(VI): Reaction Kinetics and Mechanism. Environmental Science & Technology 43(2), 509-515.


kinetics vs pH & degradation pathways

used synthesis of Delaude & Laszlo (1996)

Experimental studies were conducted to examine the oxidation of carbamazepine, an anticonvulsant drug widely detected in surface waters and sewage treatment effluent, by potassium salts of permanganate (Mn(VII); KMnO(4)) and ferrate (Fe(VI); K(2)FeO(4)). Results show that both Mn(VII) and Fe(VI) rapidly oxidize carbamazepine by electrophilic attack at an olefinic group in the central heterocyclic ring, leading to ring-opening and a series of organic oxidation products. Reaction kinetics follow a generalized second-order rate law, with apparent rate constants at pH 7.0 and 25 degrees C of 3.0(+/- 0.3) x 10(2) M(-1) s(-1) for Mn(VII) and 70(+/- 3) M(-1) s(-1) for Fe(VI). Mn(VII) reaction rates exhibit no pH dependence, whereas Fe(VI) reaction rates increase dramatically with decreasing pH, due to changing acid-base speciation of Fe(VI). Further studies with Mn(VII) show that most common nontarget water constituents, including natural organic matter, have no significant effect on rates of carbamazepine oxidation; reduced metals and (bi)sulfide exert a stoichiometric Mn(VII) demand that can be incorporated into the kinetic model. The removal of carbamazepine in two utility source waters treated with KMnO(4) agrees closely with predictions from the kinetic model that was parametrized using experiments conducted in deionized water at much higher reagent concentrations.
Anquandah, G.A.K. and Sharma, V.K. (2009) Oxidation of octylphenol by ferrate(VI). Journal of Environmental Science and Health Part a-Toxic/Hazardous Substances & Environmental Engineering 44(1), 62-66.
The rates of the oxidation of octylphenols (OP) by potassium ferrate(VI) (K(2)FeO(4)) in water were determined as a function of pH (8.0-10.9) at 25 degrees C. The rate law for the oxidation of OP by Fe(VI) was found to be first order with each reactant. The observed second-order rate constants, k(obs), for the oxidation of alkylphenols decreased with an increase in pH. The speciation of Fe(VI) (HFeO(4)(-) and FeO(4)(2-)) and OP (OP-OH and OP-O(-)) species were used to determine individual rate constants of the reactions. Comparison of rate constants and half-lives of oxidation of OP by Fe(VI) with nonylphenol (NP) and bisphenol-A (BPA) were conducted to demonstrate that Fe(VI) efficiently oxidizes environmentally relevant alkylphenols in water.
Yu, M., G. Park, and H. Kim. 2008. Oxidation of Nonylphenol Using Ferrate, p. 389-403, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. Nonylphenol Public concerns on nonylphenol (NP) and nonylphenol ethoxylates (NPEOs) are growing because they are frequently detected in the aquatic environment and proven endocrine disrupter compounds (EDCs). Since these compounds cannot be biologically completely degraded, chemical oxidation has been frequently applied to degrade NP and NPEOs. In this study, ferrate(VI) (Fe(VI)) was used to oxidize NP and its oxidation kinetics was evaluated. It should, however, be noted that the first order rate was evaluated using data collected only after the initial degradation phase, in which 50-70 % Np was degraded. In fact, the NP and Fe(VI) concentrations during the ID phase could not be quantified since the oxidation was too fast. The effect of hydrogen peroxide (H2O2) presence on the NP oxidation by Fe(VI) was also evaluated. In general, the initial destruction of NP by Fe(VI) at lower pH was more significant than higher pH (i.e., 26% at pH 9.0 and 71% at pH 6.0). H2O2 addition did not have much impact on the NP oxidation. When applied to oxidation of NP in natural water, Fe(VI) showed less removal efficiency possibly due to the presence of dissolved organics in the water.
Sharma V.K., N. Noorhasan Nadine, K. Mishra Santosh, and N. Nesnas. 2008. Ferrate(VI) Oxidation of Recalcitrant Compounds: Removal of Biological Resistant Organic Molecules by Ferrate(VI), p. 339-349, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. EDTA & Sulfamethoxazole The oxidation of recalcitrant compounds, ethylenediaminetetraacetate (EDTA) and sulfamethoxazole (SMX) by ferrate(VI) (Fe(VI), FeVIO42-) is presented. Kinetics of the reactions were determined as a function of pH at 25 °C by a stopped-flow technique. The rate law for the oxidation of these compounds by Fe(VI) is first-order with respect to each reactant. The observed second-order rate constants for the reaction of Fe(VI) with SMX decreased non-linearly with increase in pH and are possibly related to protonations of Fe(VI) and compounds. The individual rate constants, k (M-1s-1) of Fe(VI) species, HFeO4- and FeO42- with protonated and deprotonated forms of compounds were estimated. The HFeO4- species reacts much faster with these compounds than does the FeO42- species. The results showed that Fe(VI) has the potential to serve as an environmentally-friendly oxidant for removing biologically resistant organic molecules within minutes and converting them to relatively less toxic by-products in water.
Sharma, V.K. and Mishra, S.K. (2006) Ferrate(VI) oxidation of ibuprofen: A kinetic study. Environmental Chemistry Letters 3(4), 182-185.
The kinetics of ferrate(VI) ((FeO42-)-O-VI, Fe(VI)) oxidation of an antiphlogistic drug, ibuprofen (IBP), as a function of pH (7.75-9.10) and temperature (25-45 degrees C) were investigated to see the applicability of Fe(VI) in removing this drug from water. The rates decrease with an increase in pH and the rates are related to protonation of ferrate(VI). The rates increase with an increase in temperature. The E-a of the reaction at pH 9.10 was calculated as 65.4 +/- 6.4 kJ mol(-1). The rate constant of the HFeO4- with ibuprofen is lower than with the sulphur drug, sulfamethoxazole. The use of Fe(VI) to remove ibuprofen is briefly discussed.
Li, X.Z., B.L. Yuan, and N. Graham. 2008. Degradation of Dibutyl Phthalate in Aqueous Solution by a Combined Ferrate and Photocatalytic Oxidation Process, p. 364-377, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. Dibutyl Phthalate The aim of the present work was to study the interaction of ferrate oxidation and photocatalytic oxidation in terms of dibutyl phthalate (DBP) degradation in aqueous solution, in which three sets of experiments were carried out, including (1) ferrate oxidation alone, (2) photocatalytic oxidation alone, and (3) the combination of ferrate oxidation and photocatalytic oxidation. Laboratory experiments demonstrated that ferrate oxidation and phtotocatalytic oxidation of DBP in aqueous solution are relatively slow processes. However, the presence of TiO2 and ferrate together under UV illumination accelerated the DBP degradation significantly. Since ferrate was reduced quickly due to the presence of TiO2 and UV irradiation, the DBP degradation reaction can be divided into two phases. During the first 30 min (Phase 1) the DBP was degraded by both photocatalytic oxidation and ferrate oxidation, and by interactive reactions. After 30 min (Phase 2), the ferrate residual had declined to a very low level and the photocatalytic reaction was the dominant mechanism of further DBP degradation. The influence of three main factors, ferrate dosage, TiO2 dosage and pH, on the DBP degradation were investigated in order to understand the reaction mechanism and kinetics.

Graham, N., Jiang, C.C., Li, X.Z., Jiang, J.Q. and Ma, J. (2004) The influence of pH on the degradation of phenol and chlorophenols by potassium ferrate. Chemosphere 56(10), 949-956.

TCE & chlorophenol kinetics

Goff & Murmann (1971) synthesis

This paper presents information concerning the influence of solution pH on the aqueous reaction between potassium ferrate and phenol and three chlorinated phenols: 4-chlorophenol (Cl?), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP). The redox potential and aqueous stability of the ferrate ion, and the reactivity of dissociating compounds, are known to be pH dependent. Laboratory tests have been undertaken over a wide range of pH (5.8-11) and reactant concentrations (ferrate: compound molar ratios of 1:1 to 8:1). The reactivity of trichloroethylene was also investigated as a reference compound owing to its non-dissociating nature. The extent of compound degradation by ferrate was found to be highly pH dependent, and the optimal pH (maximum degradation) decreased in the order: phenol/CP, DCP, TCP; at the optimal pH the degree of degradation of these compounds was similar. The results indicate that for the group of phenol and chlorophenols studied, the presence of an increasing number of chlorine substituent atoms corresponds to an increasing reactivity of the undissociated compound, and a decreasing reactivity of the dissociated compound.
Bielski, B.H.J. and Thomas, M.J. (1987) Studies of Hypervalent Iron in Aqueous Solutions. 1. Radiation-induced Reduction of Iron (VI) to Iron (V) by CO2. Journal of the American Chemical Society 109(25), 7761-7764. includes absorbance spectra for ferrate  
Goff, H. and Murmann, R.K. (1971) Studies on Mechanism of Isotopic Oxygen Exchange and Reduction of Ferrate (VI) ion (FeO42-). Journal of the American Chemical Society 93(23), 6058-&.
source of synthetic method used by Ma's group  


Papers Focusing on Ferrate Disinfection
Citation Notes Abstract
Gombos, E., Felfoldi, T., Barkacs, K., Vertes, C., Vajna, B. and Zaray, G. (2012) Ferrate treatment for inactivation of bacterial community in municipal secondary effluent. Bioresource Technology 107, 116-121. HPC and chlorine resistant bacteria This paper demonstrates the effect of ferrate [Fe(VI)-compound], an environmental friendly multi-purpose reagent, in municipal secondary effluent treatment. The purpose was to study the inactivation capability of ferrate and for the first time to compare the effect and efficiency of Fe(VI) with the widely used disinfectant, chlorine gas on the indigenous bacterial community in the case of secondary effluents. The most probable number technique (MPN) was applied for the determination of cultivable heterotrophic bacterial abundance and terminal restriction fragment length polymorphism (T-RFLP) analysis for comparing bacterial communities. The study demonstrated that (i) ferrate and chlorine had different effect on the total bacterial community of secondary effluents, (ii) low ferrate dose [5 mg L-1 Fe(VI)] was sufficient for >99.9% reduction of indigenous bacteria, and (iii) a similar dosage was also effective in the inactivation of chlorine-resistant bacteria.
Makky, E.A., Park, G.-S., Choi, I.-W., Cho, S.-I. and Kim, H. (2011) Comparison of Fe(VI) (FeO(4)(2-)) and ozone in inactivating Bacillus subtilis spores. Chemosphere 83(9), 1228-1233.
used pH 9 borate buffered ferrate made according to Thompson et al (1951) The protozoan parasites such as Cryptosporidium parvum and Giardia lamblia have been recognized as a frequent cause of recent waterborne disease outbreaks because of their strong resistance against chlorine disinfection. In this study, ozone and Fe(VI) (i.e., FeO(4)(2-)) were compared in terms of inactivation efficiency for Bacillus subtilis spores which are commonly utilized as an indicator of protozoan pathogens. Both oxidants highly depended on water pH and temperature in the spore inactivation. Since redox potential of Fe(VI) is almost the same as that of ozone, spore inactivation efficiency of Fe(VI) was expected to be similar with that of ozone. However, it was found that ozone was definitely superior over Fe(VI): at pH 7 and 20 degrees C, ozone with the product of concentration x contact time (T) of 10 mg L(-1) min inactivate the spores more than 99.9% within 10 min, while Fe(VI) with (C) over barT of 30 mg L(-1) min could inactivate 90% spores. The large difference between ozone and Fe(VI) in spore inactivation was attributed mainly to Fe(III) produced from Fe(VI) decomposition at the spore coat layer which might coagulate spores and make it difficult for free Fe(VI) to attack live spores.
Hu, L., Page, M., Marinas, B., Shisler, J.L. and Strathmann, T.J. (2008) Treatment of Emerging Pathogens and Micropollutants with Potassium Ferrate(VI), WQTC Proceedings, Cincinnati.   This study reports on recent work examining the effectiveness ofFe(VI) for oxidation of pharmaceutically active compounds (PhACs) and inactivation of viral pathogens (surrogate pathogen: coliphage MS2) during water treatment. Twelve PhACs from representative compound classes were screened to assess potential reactivity with Fe(VI) on timescales of interest to water utilities. Eight of the 12 PhACs surveyed, including the antiepileptic drug carbamazepine and phenolic endocrine disruptor compounds (EDCs), were found to have moderate to high reactivity with Fe(VI). Results also show that Fe(VI) is an effective disinfectant for MS2 phage. The CT value for 99% inactivation ofMS2 is ~2 mg-min L-1 as Fe at pH 7 and 25 °C. Both rates ofPhAC oxidation and virus inactivation are highly dependent upon solution pH, increasing with decreasing pH as Fe(VI) speciation shifts towards more reactive protonated species (HFe04- and H2Fe04). Kinetic models that consider changing speciation of both Fe(VI) and the reacting PhAC or virus, illustrated for the case of carbamazepine, were developed to account for pH-dependent reactivity trends.


Papers on General Ferrate Treatment (W & WW)
Citation Notes Abstract
Prucek, R., J. Tucek, et al. (2013). "Ferrate(VI)-Induced Arsenite and Arsenate Removal by In Situ Structural Incorporation into Magnetic Iron(III) Oxide Nanoparticles." Environmental Science & Technology 47(7): 3283-3292. Arsenic removal by insitu formation of nano-Fe2O3 We report the first example of arsenite and arsenate removal from water by incorporation of arsenic into the structure of nanocrystalline iron(III) oxide. Specifically, we show the capability to trap arsenic into the crystal structure of gamma-Fe2O3 nanoparticles that are in situ formed during treatment of arsenic-bearing water with ferrate(VI). In water, decomposition of potassium ferrate(VI) yields nanoparticles having core-shell nanoarchitecture with a gamma-Fe2O3 core and a gamma-FeOOH shell. High-resolution X-ray photoelectron spectroscopy and in-field Fe-57 Mossbauer spectroscopy give unambiguous evidence that a significant portion of arsenic is embedded in the tetrahedral sites of the gamma-Fe2O3 spinel structure. Microscopic observations also demonstrate the principal effect of As doping on crystal growth as reflected by considerably reduced average particle size and narrower size distribution of the "in-situ" sample with the embedded arsenic compared to the "ex-situ" sample with arsenic exclusively sorbed on the iron oxide nanoparticle surface. Generally, presented results highlight ferrate(VI) as one of the most promising candidates for advanced technologies of arsenic treatment mainly due to its environmentally friendly character, in situ applicability for treatment of both arsenites and arsenates, and contrary to all known competitive technologies, firmly bound part of arsenic preventing its leaching back to the environment. Moreover, As-containing gamma-Fe2O3 nanoparticles are strongly magnetic allowing their separation from the environment by application of an external magnet.
Horst, C., V. K. Sharma, et al. (2013). "Organic matter source discrimination by humic acid characterization: Synchronous scan fluorescence spectroscopy and Ferrate(VI)." Chemosphere 90(6): 2013-2019. Impacts on NOM fluorescence In this study, seven soil and sedimentary humic acid samples were analyzed by synchronous scan fluorescence (SSF) spectroscopy. The spectra of these humic acids were compared to each other and characterized, based on three major SSF peaks centered at approximately 281,367 and 470 nm. Intensity ratios were calculated based on these peaks that were used to numerically assist in source discrimination. All humic acid samples were then reacted with Ferrate(VI) and were again analyzed with SSF. Upon the addition of Ferrate(VI) SSF spectra were obtained which more readily differentiated humic acid source. This method will assist geochemists and water management districts in tracing sources of organic matter to receiving water bodies and may aid in the elucidation of the chemical nature of humic acids
Graham, N.J.D., Khoi, T.T. and Jiang, J.Q. (2010) Oxidation and coagulation of humic substances by potassium ferrate. Water Science and Technology 62(4), 929-936.

floc index & TOC removal were main indicators

used Li et al. (2005) for ferrate synthesis and Lee et al. (2005) for verification

Ferrate (FeO(4)(2-)) is believed to have a dual role in water treatment, both as oxidant and coagulant Few studies have considered the coagulation effect in detail, mainly because of the difficulty of separating the oxidation and coagulation effects This paper summarises some preliminary results from laboratory-based experiments that are investigating the coagulation reaction dynamically via a PDA instrument, between ferrate and humic acid (HA) at different doses and pH values, and comparing the observations with the use of ferric chloride The PDA output gives a comparative measure of the rate of floc growth and the magnitude of floc formation The results of the tests show some significant differences in the pattern of behaviour between ferrate and ferric chloride At pH 5 the chemical dose range (as Fe) corresponding to HA coagulation was much broader for ferrate than ferric chloride, and the optimal Fe dose was greater Ferrate oxidation appears to increase the hydrophilic and electronegative nature of the HA leading to an extended region of charge neutralisation A consequence of the ferrate oxidation is that the extent of HA removal was slightly lower (similar to 5%) than with ferric chloride At pH 7, in the sweep flocculation domain, ferrate achieved much greater floc formation than ferric chloride, but a substantially lower degree of HA removal
Tien Khoi, T., N. Graham, and J.-Q. Jiang. 2008. Evaluating the Coagulation Performance of Ferrate: A Preliminary Study, p. 292-305, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. a preliminary version of the WS&T 2010 paper Ferrate is cited as having a dual role in water treatment, both as oxidant and coagulant. Few studies have considered the coagulation effect in detail, mainly because of the difficulty of separating the oxidation and coagulation effects. This paper summarises some preliminary results from an ongoing laboratory-based project that is investigating the coagulation reaction, dynamically via a PDA instrument, between ferrate and a suspension of kaolin powder at different doses and pH values, and comparing the observations with the use of ferric chloride. The PDA output gives a comparative measure of the rate of floc growth and the magnitude of floc formation. The results of the tests show some similarities and significant differences in the pattern of behaviour between ferrate and ferric chloride. This paper presents and discusses these observations and provides some comparative information on the strength of flocs formed.

Jiang, J.Q., Lloyd, B. and Grigore, L. (2001) Preparation and evaluation of potassium ferrate as an oxidant and coagulant for potable water treatment. Environmental Engineering Science 18(5), 323-328.

proprietary preparation of ferrate; some THMFP destruction data Potassium ferrate was prepared using a new method, and its disinfection/coagulation performance for water treatment has been evaluated. The study results demonstrated that farrate could act as a dual-function chemical reagent (i.e., oxidant and coagulant) for drinking-water treatment, and performs better than ferric sulphate at lower doses for treating upland colored water. The ferrate can effectively remove natural organic matter (as UV254) and turbidity, and kills total coliforms (100%) at very low doses. In addition, under the optimal study conditions, the residual iron concentration and trihalomethane formation potential (THMFP) of the ferrate treated water are below that of drinking water standards.
Jiang, J.Q., Stanford, C. and Alsheyab, M. (2009) The online generation and application of ferrate(VI) for sewage treatment-A pilot scale trial. Separation and Purification Technology 68(2), 227-231.

wastewater application with electrochemical generator

BOD, COD and P reductions

Ferrate(VI) is an oxidant; under acidic conditions, the redox potential of ferrate(VI) salt is the strongest among all oxidants used for water and wastewater treatment. Ferrate(VI) is also a coagulant; during the oxidation process, ferrate(VI) ions are reduced to Fe(III) ions or ferric hydroxide, which simultaneously generates a coagulant in a single dosing and mixing unit process. The superior performance of ferrate(VI) as an oxidant/disinfectant and coagulant in water and wastewater treatment has been extensively studied. However, challenges have existed to the implementation of ferrate(VI) technology in water and wastewater treatment practice due to the instability of the ferrate(VI) solutions and a high preparation cost of a solid ferrate(VI). It would be an ideal approach to generate ferrate(VI) in situ and apply the generated ferrate(VI) directly for wastewater treatment. This paper reports the online preparation and use of ferrate(VI) for sewage treatment at a pilot scale applied in a wastewater treatment plant in the UK. The technology has been demonstrated to be promising in terms of removing suspended solids, phosphate, COD and BOD at a very low dose range, 0.005-0.04 mg l(-1) as Fe(6+) in comparison with a normal coagulant, ferric sulphate at high doses, ranging between 25 and 50 mg l(-1) as Fe(3+). in terms of the similar sewage treatment performance achieved, the required dose with ferrate(VI) was 100 times less than that with ferric sulphate. However, the full operating cost needs further assessment before the ferrate(VI) technology could be implemented in a full scale water or wastewater treatment.
Jiang, J.Q. and Wang, S. (2003) Enhanced coagulation with potassium ferrate(VI) for removing humic substances. Environmental Engineering Science 20(6), 627-633.

1185 molar absorptivity @504 nm

DOC & THMFP removal data

Potassium ferrate (K2FeO4) has the strongest oxidation strength among all the oxidants/disinfectants practically used for water and wastewater treatment. Apart from this, in the oxidation process, ferrate(VI) ions are reduced to Fe(III) ions or ferric hydroxide, and this simultaneously generates a coagulant in a single dosing and mixing unit process. This paper demonstrates that potassium ferrate can perform better than ferric sulphate at lower doses for treating waters containing humic and fulvic acids in terms of removing UV254 absorbance and dissolved organic carbon (DOC) and lowering the trihalomethane formation potential (THMFP), indicating that the potassium ferrate is a potential water treatment chemical for "enhanced coagulation."
Lee, Y., Um, I.H. and Yoon, J. (2003) Arsenic(III) oxidation by iron(VI) (ferrate) and subsequent removal of arsenic(V) by iron(III) coagulation. Environmental Science & Technology 37(24), 5750-5756.

used synthesis of Delaud & Laszlo (1996)

good kinetic study of As oxidation

We investigated the stoichiometry, kinetics, and mechanism of arsenite [As(III)] oxidation by ferrate [Fe(VI)] and performed arsenic removal tests using Fe(VI) as both an oxidant and a coagulant. As(III) was oxidized to As(V) (arsenate) by Fe(VI), with a stoichiometry of 3:2 [As(III):Fe(VI)]. Kinetic studies showed that the reaction of As(III) with Fe(VI) was first-order with respect to both reactants, and its observed second-order rate constant at 25 degreesC decreased nonlinearly from (3.54 +/- 0.24) x 10(5) to (1.23 +/- 0.01) x 10(3) M-1 s(-1) with an increase of pH from 8.4 to 12.9. A reaction mechanism by oxygen transfer has been proposed for the oxidation of As(III) by Fe(VI). Arsenic removal tests with river water showed that, with minimum 2.0 mg L-1 Fe(VI), the arsenic concentration can be lowered from an initial 517 to below 50 mug L-1, which is the regulation level for As in Bangladesh. From this result, Fe(VI) was demonstrated to be very effective in the removal of arsenic species from water at a relatively low dose level (2.0 mg L-1). In addition, the combined use of a small amount of Fe(VI) (below 0.5 mg L-1) and Fe(III) as a major coagulant was found to be a practical and effective method for arsenic removal.
Licht, S., X. Yu, and D. Qu. 2008. Electrochemical Fe(VI) Water Purification and Remediation, p. 268-291, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. Fe(VI) generation and oxidation of N species A novel on-line electrochemical Fe(VI) water purification methodology is introduced, which can quickly oxidize and remove a wide range of both inorganic and organic water contaminants. Fe(VI) is an unusual and strongly oxidizing form of iron, which provides a potentially less hazardous water purifying agent than chlorine. However, a means of Fe(VI) addition to the effluent had been a barrier to its effective use in water remediation, as solid Fe(VI) salts require complex (costly) syntheses steps, and solutions of Fe(VI) decompose. On-line electrochemical Fe(VI) water purification avoids these limitations, in which Fe(VI) is directly prepared in solution from an iron anode as the FeO42- ion, and is added to the contaminant stream. Added FeO42- decomposes, by oxidizing water contaminants. Demonstration of this methodology is performed with inorganic contaminants sulfides, cyanides and arsenic; and water soluble organic contaminants including phenol, aniline and hydrazine. In addition, removal of the oxidation products by following an activated carbon filter at the downstream of the on-line configuration is also presented.
Ma, J., W. Liu, Y. Zhang, and C. Li. 2008. Enhanced Removal of Cadmium and Lead from Water by Ferrate Preoxidation in the Process of Coagulation, p. 456-465, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. removal of Cd & Pb by coagulation This paper discussed the effect of ferrate preoxidation on enhanced removal of cadmium and lead from water in the process of coagulation. Some factors affecting the removal of heavy metals were discussed such as pH value, the dosage of ferrate and the water quality condition etc. The results showed that ferrate preoxidation could effectively increase the removal efficiency of lead, whilst a little increase of removal efficiency of cadmium; the removal efficiency increased with the increase of pH. The presence of humic acid greatly affected the removal efficiency of lead in the process of coagulation, but hardly affected the removal efficiency of cadmium. The combined effect of adsorption by intermediate iron species formed in the process of ferrate oxidation and the enhanced coagulation of iron colloids co-precipitated with heavy metals might be responsible for the effective removal of heavy metals.
Licht, S. and Yu, X.W. (2005) Electrochemical alkaline Fe(VI) water purification and remediation. Environmental Science & Technology 39(20), 8071-8076.

CN, HS-, As remediation

mostly about ferrate production

Fe(VI) is an unusual and strongly oxidizing form of iron, which provides a potentially less hazardous water-purifying agent than chlorine. A novel on-line electrochemical Fe(VI) water purification methodology is introduced. Fe(VI) addition had been a barrier to its effective use in water remediation, because solid Fe(VI) salts require complex (costly) syntheses steps and solutions of Fe(VI) decompose. Online electrochemical Fe(VI) water purification avoids these limitations, in which Fe(VI) is directly prepared in solution from an iron anode as the FeO42- ion, and is added to the contaminant stream. Added FeO42- decomposes, by oxidizing a wide range of water contaminants including sulfides (demonstrated in this study) and other sulfur-containing compounds, cyanides (demonstrated in this study), arsenic (demonstrated in this study), ammonia and other nitrogen-containing compounds (previously demonstrated), a wide range of organics (phenol demonstrated in this study), algae, and viruses (each previously demonstrated).
Lim, M. and Kim, M.-J. (2010) Effectiveness of Potassium Ferrate (K(2)FeO(4)) for Simultaneous Removal of Heavy Metals and Natural Organic Matters from River Water. Water Air and Soil Pollution 211(1-4), 313-322.

data on removal of metals & NOM

used Delaude & Laszlo (1996) synthesis

This study has investigated how to simultaneously remove both heavy metals (Cu, Mn, and Zn) and natural organic matters (NOM; humic acid and fulvic acid) from river water using potassium ferrate (K(2)FeO(4)), a multipurpose chemical acting as oxidant, disinfectant, and coagulant. In water sample including each 0.1 mM heavy metal, its removal efficiency ranged 28-99% for Cu, 22-73% for Mn, and 18-100% for Zn at the ferrate(VI) doses of 0.03-0.7 mM (as Fe). The removal efficiency of each heavy metal increased with increasing pH, whereas an overall temperature did not make any special effect on the reaction between the heavy metal and ferrate(VI). A high efficiency was achieved on the simultaneous treatment of heavy metals (0.1 mM) and NOM (10 mg/l) at the ferrate(VI) doses of 0.03-0.7 mM (as Fe): 87-100% (Cu), 31-81% (Mn), 11-100% (Zn), and 33-86% (NOM). In the single heavy metal solution, the optimum ferrate dose for treating 0.1 mM Cu or Mn was 0.1 mM (as Fe), while that for treating 0.1 mM Zn was 0.3 mM (as Fe). In the mixture of three heavy metals and NOM, on the other hand, 0.5 mM (as Fe) ferrate(VI) was determined as an optimum dose for removing both 0.1 mM heavy metals (Cu, Mn, and Zn) and 10 mg/l NOM. Prior to the addition of ferrate(VI) into the solution of heavy metals and NOM (HA or FA), complexes were formed by the reaction between divalent cations of heavy metals and negatively charged functional groups of NOM, enhancing the removal of both heavy metals and NOM by ferrate(VI).
Liu, W., and Y.-M. Liang. 2008. Use of Ferrate(VI) in Enhancing the Coagulation of Algae-Bearing Water: Effect and Mechanism Study, p. 434-445, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. impacts on algae removal by coagulation and UV absorbance This study found that ferrate preoxidation significantly enhanced the algae removal in alum coagulation. A very short preoxidation time, e.g. several minutes, was enough to achieve substantial enhancement of algae removal by ferrate. It was also found that ferrate preoxidation was much more powerful than pre-chlorination in enhancing the coagulation of algae-bearing water. Ferrate oxidation left obvious impacts on surface architecture of algal cells. Upon oxidation with ferrate, the cells were inactivated and some intracellular and extracelluar components were released into the water, which act as coagulant aid. The coagulation was also improved by increasing particle concentration in water, because of the formation of the intermediate forms of precipitant iron species during preoxidation. In addition, it was also observed that ferrate preoxidation caused algae agglomerate formation before the addition of coagulant, the subsequent application of alum resulted in further coagulation. Ferrate preoxidation also improved the reduction of residual organic matters in algae-bearing water.
Ma, J. and Liu, W. (2002) Effectiveness and mechanism of potassium ferrate(VI) preoxidation for algae removal by coagulation. Water Research 36(4), 871-878.

algae removal is improved

used synthesis method of Goff & Murmann (1971)

Jar tests were conducted to evaluate the effectiveness of potassium ferrate preoxidation on algae removal by coagulation. Laboratory studies demonstrated that pretreatment with potassium ferrate obviously enhanced the algae removal by coagulation with alum [Al-2(SO4)(3) . 18H(2)O]. Algae removal efficiency increased remarkably when the water was pretreated with ferrate. A very short time of preoxidation was enough to achieve substantial algae removal efficiency, and the effectiveness was further increased at a prolonged pretreatment time. Pretreatment with ferrate resulted in a reduction of alum dosage required to cause an efficient coagulation for algae removal. The obvious impact of cell architecture by potassium ferrate was found through scanning electron microscopy. Upon oxidation with ferrite, the cells were inactivated and some intracellular and extracelluar components were released into the water. which may be helpful to the coagulation by their bridging effect. Efficient removal of algae by potassium ferrite preoxidation is believed to be a consequence of several process mechanisms. Ferrate preoxidation inactivated algae. induced the formation of coagulant aid, which are the cellular components secreted by algal cells. The coagulation was also improved by increasing particle concentration in water, because of the formation of the intermediate forms of precipitant iron species during preoxidation. In addition, it was also observed that ferrite preoxidation caused algae agglomerate formation before the addition of coagulant, the subsequent application of alum resulted in further coagulation.
Ma, J., C. Li, Y. Zhang, and R. Ju. 2008. Combined Process of Ferrate Preoxidation and Biological Activated Carbon Filtration for Upgrading Water Quality, p. 446-455, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. impacts on coagulation wrt NOM removal and size The preoxidation of polluted surface water with ferrate was conducted with respect to its impact on the following biofiltration. It was found that preoxidation with ferrate promoted the biodegradation of organics with substantial reductions of chemical oxygen demand (CODMn), UV254-absorbance. It was also found that the removal of NH4+-N in biological activated carbon (BAC) process was also substantially improved as compared with the cases without ferrate preoxidation and with ozone preoxidation. In addition, the experiments were conducted related to the effect of potassium ferrate oxidation of raw water of Songhua River on its changes of molecular weight distribution in order to investigate further the enhancement of ferrate preoxidation on the removal of organics. The results indicated that the concentration of organics with molecular weight (MW) of 10k-100k and less than 0.5k were substantially increased after the raw water was coagulated with ferrate preoxidation, which suggested that these oxidation products are readily removed by subsequent biofiltration.
White, D.A., and G.S. Franklin. 1998. A preliminary investigation into the use of sodium ferrate in water treatment. Environmental Technology 19:1157-1160. Mn and color removal This paper describes some preliminary tests on the use of sodium ferrate as a reagent for drinking water treatment. me manufacture and purification of the reagent by a low temperature method is described. Tests were carried out for colour and manganese removal using the ferrate as a flocculant. There is some indication that much less ferrate than ferric flocculant is needed for colour removal. Sodium ferrate is also an effective remover of manganese.
Ramseier, M.K., Peter, A., Traber, J. and von Gunten, U. (2011) Formation of assimilable organic carbon during oxidation of natural waters with ozone, chlorine dioxide, chlorine, permanganate, and ferrate. Water Research 45(5), 2002-2010. and supporting info
AOC formation & discussion on pathways and oxalate yields Five oxidants, ozone, chlorine dioxide, chlorine, permanganate, and ferrate were studied with regard to the formation of assimilable organic carbon (AOC) and oxalate in absence and presence of cyanobacteria in lake water matrices. Ozone and ferrate formed significant amounts of AOC, i.e. more than 100 mu g/L AOC were formed with 4.6 mg/L ozone and ferrate in water with 3.8 mg/L dissolved organic carbon. In the same water samples chlorine dioxide, chlorine, and permanganate produced no or only limited AOC. When cyanobacterial cells (Aphanizomenon gracile) were added to the water, an AOC increase was detected with ozone, permanganate, and ferrate, probably due to cell lysis. This was confirmed by the increase of extracellular geosmin, a substance found in the selected cyanobacterial cells. AOC formation by chlorine and chlorine dioxide was not affected by the presence of the cells. The formation of oxalate upon oxidation was found to be a linear function of the oxidant consumption for all five oxidants. The following molar yields were measured in three different water matrices based on oxidant consumed: 2.4-4.4% for ozone, 1.0-2.8% for chlorine dioxide and chlorine, 1.1-1.2% for ferrate, and 11-16% for permanganate. Furthermore, oxalate was formed in similar concentrations as trihalomethanes during chlorination (yield similar to 1% based on chlorine consumed). Oxalate formation kinetics and stoichiometry did not correspond to the AOC formation. Therefore, oxalate cannot be used as a surrogate for AOC formation during oxidative water treatment.
Schuck, C.A., De Luca, S.J., Ruaro Peralba, M.d.C. and De Luca, M.A. (2006) Sodium ferrate (IV) and sodium hypochlorite in disinfection of biologically treated effluents. Ammonium nitrogen protection against THMs and HAAs. Journal of Environmental Science and Health Part a-Toxic/Hazardous Substances & Environmental Engineering 41(10), 2329-2343.
ferrate added to treated WW - not much affect The work described in this paper presents an evaluation of disinfection by-products generation in four different biological treatment plant effluents, making use of sodium hypochlorite and sodium ferrate (IV) at varying concentration and reaction time. Correlations between pH, chemical oxygen demand, total organic carbon, ammonium nitrogen, combined chlorine and trihalomethanes (THMs) and haloacetic acids (HAAs) were carried out. Disinfection by-products generation presented a direct relation with concentration and sodium hypochlorite reaction time. For the highest hypochlorite concentration employed (20 mg L-1) and highest reaction time (168 h), the THMs total did not exceed 312.96 mu g L-1, a value that lies below the Brazilian emission standard for treated effluents (1 mg L-1 of chloroform). The THMs presented an inverse correlation with ammonium nitrogen, when inverse (R-2 = 0.646; P < 0.001) and exponential (R-2 = 0.707; P < 0.001) function were used. As per HAAs this same relation was observed for logarithmic (R-2 = 0.0397 P < 0.001) and exponential (R-2 = 0.508; P < 0.001) functions. The more nitrified the effluent, the bigger the chlorinated disinfection by-product generation. The disinfectant sodium ferrate (IV) does not lead to halogenated by-product formation.
Jiang, J.-Q., and K. Sharma Virender. 2008. The Use of Ferrate(VI) Technology in Sludge Treatment, p. 306-325, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. some disinfection data, control of metals, odors Sludge in large quantity is generated as byproducts of wastewater treatment processes. Various approaches have been taken to treat sludge, such as land-filling, ocean dumping, or recycling for beneficial purposes. In the USA, about 60% of sludge generated is land applied as a soil conditioner or fertilizer. Due to increasing public concern on the safety of land-applied sludge, various sludge treatment technologies are being developed or under evaluation in order to improve the quality of sludge in terms of pathogen content, odor characteristics, accumulated organic micro-pollutants. This paper summarizes the results of various reported or on-going researches on the potential use of ferrate [Fe(VI)O42-] as a conditioning agent for sludge. Ferrate(VI) has high oxidizing potential and selectivity, and upon decomposition produces a non-toxic by-product, Fe(III), which is a conventional coagulant; the ferrate(VI) is thus considered to be an environmentally-friendly oxidant. Rates of oxidation reactions increase with decrease in pH. Oxidation of sulfur- and amine-containing contaminants in sludge by Fe(VI) can be accomplished in seconds to minutes with formation of non-hazardous products. Ferrate(VI) can also coagulate toxic metals and disinfect wide ranges of microorganisms including human pathogens. With its multifunctional properties, ferrate(VI) has the potential for sludge treatment.
Stanford, C., Jiang, J.Q. and Alsheyab, M. (2010) Electrochemical Production of Ferrate (Iron VI): Application to the Wastewater Treatment on a Laboratory Scale and Comparison with Iron (III) Coagulant. Water Air and Soil Pollution 209(1-4), 483-488.
removal of SS, BOD, COD & P in WWT This paper presents a comparative study of the performance of ferrate(VI), FeO (4) (2-) , and ferric, Fe(III), towards wastewater treatment. The ferrate(VI) was produced by electrochemical synthesis, using steel electrodes in a 16 M NaOH solution. Domestic wastewater collected from Hailsham North Wastewater Treatment Works was treated with ferrate(VI) and ferric sulphate (Fe(III)). Samples were analysed for suspended solids, chemical oxygen demand (COD), biochemical oxygen demand (BOD) and P removal. Results for low doses of Fe(VI) were validated via a reproducibility study. Removal of phosphorous reached 40% with a Fe(VI) dose as low as 0.01 mg/L compared to 25% removal with 10 mg/L of Fe(III). For lower doses (< 1 mg/L as Fe), Fe(VI) can achieve between 60% and 80% removals of SS and COD, but Fe(III) performed even not as well as the control sample where no iron chemical was dosed. The ferrate solution was found to be stable for a maximum of 50 min, beyond which Fe(VI) is reduced to less oxidant species. This provided the maximum allowed storage time of the electrochemically produced ferrate(VI) solution. Results demonstrated that low addition of ferrate(VI) leads to good removal of P, BOD, COD and suspended solids from wastewater compared to ferric addition and further studies could bring an optimisation of the dosage and treatment.
Filip, J., Yngard, R.A., Siskova, K., Marusak, Z., Ettler, V., Sajdl, P., Sharma, V.K. and Zboril, R. (2011) Mechanisms and Efficiency of the Simultaneous Removal of Metals and Cyanides by Using Ferrate(VI): Crucial Roles of Nanocrystalline Iron(III) Oxyhydroxides and Metal Carbonates. Chemistry-a European Journal 17(36), 10097-10105.
study of precipitates, XPS, TEM, FTIR data The reaction of potassium ferrate(VI), K(2)FeO(4), with weak-acid dissociable cyanides-namely, K(2)[Zn(CN)(4)], K(2)[Cd(CN)(4)], K(2)[Ni(CN)(4)], and K(3)[Cu(CN)(4)]-results in the formation of iron(III) oxyhydroxide nanoparticles that differ in size, crystal structure, and surface area. During cyanide oxidation and the simultaneous reduction of iron(VI), zinc(II), copper(II), and cadmium(II), metallic ions are almost completely removed from solution due to their co-precipitation with the iron(III) oxyhydroxides including 2-line ferrihydrite, 7-line ferrihydrite, and/or goethite. Based on the results of XRD, Mossbauer and IR spectroscopies, as well as TEM, X-ray photoelectron emission spectroscopy, and Brunauer-Emmett-Teller measurements, we suggest three scavenging mechanisms for the removal of metals including their incorporation into the ferrihydrite crystal structure, the formation of a separate phase, and their adsorption onto the precipitate surface. Zn and Cu are preferentially and almost completely incorporated into the crystal structure of the iron(III) oxyhydroxides; the formation of the Cd-bearing, X-ray amorphous phase, together with Cd carbonate is the principal mechanism of Cd removal. Interestingly, Ni remains predominantly in solution due to the key role of nickel(II) carbonate, which exhibits a solubility product constant several orders of magnitude higher than the carbonates of the other metals. Traces of Ni, identified in the iron(III) precipitate, are exclusively adsorbed onto the large surface area of nanoparticles. We discuss the relationship between the crystal structure of iron(III) oxyhydroxides and the mechanism of metal removal, as well as the linear relationship observed between the rate constant and the surface area of precipitates.
Joshi Umid, M., R. Balasubramanian, and K. Sharma Virender. 2008. Potential of Ferrate(VI) in Enhancing Urban Runoff Water Quality, p. 466-476, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. review of treatment effectiveness with focus on runoff Urban development and increasing water demand are putting a lot of stress on existing water resources around the world. A great deal of attention is now paid to alternative sources of water such as stormwater catchment systems as they serve multi-purpose functions. However, human activities introduce a variety of contaminants into the stormwater catchments, which affect the quality of the water to be used for both potable and non-potable purposes. Environmentally friendly treatment technologies are needed to treat and to use urban runoff without having negative impacts on the environment. Ferrate (VI) technology has the potential to be one of the most environmentally friendly water treatment technologies of the twenty-first century. Ferrate(VI) has advantages in treating heavy metals (e.g., Pb2+, Cd2+, Cr3+, Hg2+, Cu2+, and Mn2+), suspended particles, synthetic/natural organic matter (present as TOC, BOD and COD), microorganisms (e.g., bacteria and virus), without producing chlorinated by-products. Ames test on ferrate(VI) treated water demonstrated negative results, suggesting no mutagenic by-products. Uniquely, Ferrate(VI) performs distinctly different treatment functions (oxidation, coagulation, flocculation, and disinfection) from the application of a single dose, thus providing a simplified and cost-effective process.




Ferrate Production and Stability
Citation Notes Abstract

Licht, S., Yu, X., (2008) Recent Advances in Fe(VI) Synthesis, Ferrates, 985, ACS Symposium Series, pp. 2-51. American Chemical Society.

extensive review of chemical and electrochemical methods The synthesis and analysis of a range of Fe(VI) compounds are presented. Fe(VI) compounds have also been variously referred to as ferrates or super-iron compounds. Fe(VI) salts with detailed syntheses in this paper include the alkali Fe(VI) salts high purity Cs2FeO4, Rb2FeO4, and KxNa(2-x)FeO4, low purity Li2FeO4, as well as high purity alkali earth Fe(VI) salts BaFeO4, SrFeO4, and also Ag2FeO4. Two conventional, as well as two improved Fe(VI) synthetic routes are presented. The conventional syntheses include solution phase oxidation (by hypochlorite) of Fe(III), and the synthesis of less soluble super-irons by dissolution of FeO42-, and precipitation with alternate cations. The new routes include a solid synthesis route for Fe(VI) salts and the electrochemical synthesis (include in-situ & ex-situ synthesis) of Fe(VI) salts. Fe(VI) analytical methodologies summarized are FTIR, ICP, titrimetric, UV/VIS, XRD, Mössbauer and a range of electrochemical analyses. Fe(VI) compounds have been explored as energy storage cathode materials in both aqueous and non-aqueous phase in "super-iron" battery configurations, as well as novel oxidants for synthesis and water treatment purification. Preparation of reversible Fe(VI/III) thin film towards a rechargeable super-iron cathode is also presented. In addition, the preparation of unusual KMnO4 and zirconia coatings on Fe(VI) salts, via organic solvent deposition, is summarized. These coatings can stabilize and activate Fe(VI) salts in contact with alkaline media.
Ninane, L., Kanari, N., Criado, C., Jeannot, C., Evrard, O., Neveux, N., (2008) New Processes for Alkali Ferrate Synthesis, Ferrates, 985, ACS Symposium Series, pp. 102-111. method for use in water treatment A new process for the synthesis of the potassium ferrate(VI) salt was developed at the University of Nancy, France under an EEC program; started in 2001. This program had an objective of synthesizing a large quantity of ferrate in order to feed large scale applications in the field of water treatment such as drinking water, municipal waste water, and industrial waste water treatment. The raw materials used were ferrous sulphate, potassium hydroxide, and calcium hypochlorite (or chlorine). In this process, mixing of three solids took place in a mixer in which the potassium ferrate(VI) salt was stabilized. Another objective of the program was to develop synthesis of solid sodium ferrate(VI), which is cheaper to produce because its preparation requires less expensive materials: caustic soda instead of potassium hydroxide and sodium hypochlorite (or chlorine gas) instead of calcium hypochlorite. The final objective was to develop a better technology, which could be cheaper and easier to scale-up. This chapter also describes successful results of lab and small pilot tests.

Alsheyab, M., Jiang, J.Q. and Stanford, C. (2009) On-line production of ferrate with an electrochemical method and its potential application for wastewater treatment - A review.Journal of Environmental Management 90(3), 1350-1356.


A number of studies on the oxidation of various organic/inorganic contaminants by ferrate(VI) were reported in the 1980s and 1990s. The exploration of the use of ferrate(VI) for water and wastewater treatment has been well addressed recently. However, challenges have existed for the implementation of ferrate(VI) technology in practice due to the instability of a ferrate solution or high production cost of solid ferrate products. The research has been carried out aiming at the generation and application of ferrate(VI) in situ. This paper thus reviews ferrate chemistry and its overall performance as a water treatment chemical, discusses the factors affecting the fer-rate yield efficiency using the electrochemical method, and finally, summarises the work on the production and use of ferrate in situ which is currently under study.

Alsheyab, M., Jiang, J.Q. and Stanford, C. (2010) Engineering Aspects of Electrochemical Generation of Ferrate: A Step Towards Its Full Scale Application for Water and Wastewater Treatment. Water Air and Soil Pollution 210(1-4), 203-210.   The objective of this paper is to design a pilot plant electrochemical reactor and to prove the operational concept of the electrochemical production of ferrate in situ and its online application for sewage treatment. To that end, the first part of this paper focuses on the analysis of the main engineering aspects of the reactor and the electrochemical process that affect the ferrate production, using laboratory scale experiments such as the interelectrode gap, the space-time yield, the area/volume (A/V) ratio, the current efficiency, and the energy consumption. The second part focuses on the production of ferrate using a pilot plant scale to prove the operational concept of the electrochemical generation of ferrate in situ and its online application as a step towards its full scale application for water and wastewater treatment.

Alsheyab, M., Jiang, J.Q. and Stanford, C. (2010) Electrochemical generation of ferrate (VI): Determination of optimum conditions Desalination 254(1-3), 175-178.

  The optimum conditions for the electrochemical generation of ferrate were analysed using a laboratory scale electrochemical reactor and using NaOH as the electrolyte with a reaction duration of 25 min. The criteria used for comparison are the current efficiency and the energy consumption. The conducted experiments in this project showed that the optimum current density of the 10 studied applied currents was 36 A/m(2); the optimum concentration of NaOH of the four different studied concentrations was 16 M and the optimum carbon content (C%) of the three studied steels was 0.11%.
Chengchun, J., Chen, L., Shichao, W., (2008) Preparation of Potassium Ferrate by Wet Oxidation Method Using Waste Alkali: Purification and Reuse of Waste Alkali, Ferrates, 985, ACS Symposium Series, pp. 94-101.   A new method of preparing potassium ferrate using waste alkali is developed in this report. After preparation of potassium ferrate by the wet oxidation method, the waste alkali was purified and reused for a further preparation runs. The purification of waste alkali and the temperature for the furification were studied. The results indicated that the waste alkali can be used for preparing potassium ferrate, and the purity and yield of potassium ferrate product were steadily higher than 90% and 60%, respectively after ten recycles of the waste alkali. Therefore, due to the use of waste alkali, the cost is reduced sharply, and a green synthesis for potassium ferrate is achieved.
Benová, M., Híveš, J., Bouzek, K., Sharma, V.K., (2008) Electrochemical Ferrate(VI) Synthesis: A Molten Salt Approach, Ferrates, 985, ACS Symposium Series, pp. 68-80.   The electrochemical synthesis of ferrate(VI) was studied for the first time in a molten salt environment. An eutectic NaOH-KOH melt at the temperature of 200 °C was selected as a most appropriate system for the synthesis. Cyclic voltammetry was used to characterize the processes taking place on the stationary platinum (gold) or iron electrodes. The identified anodic current peak corresponding to the ferrate(VI) production was close to the potential region at which oxygen evolution begins. During the reverse potential scan, well defined cathodic current peak corresponding to the ferrate(VI) reduction appears. However, the peak was shifted to less cathodic potential than that of potential corresponding to the electrolysis in aqueous solutions. This indicates less progressive anode inactivation in a molten salts environment.
Thompson, G.W., Ockerman, L.T. and Schreyer, J.M. (1951) Preparation and Purification of Potassium Ferrate VI. Journal of the American Chemical Society 73(3), 1379-1381. chemical synthesis used by von Gunten's group  
Li, C., Li, X.Z. and Graham, N. (2005) A study of the preparation and reactivity of potassium ferrate. Chemosphere 61(4), 537-543.
preferred synthetic method for Graham's group In the context of water treatment, the ferrate ([FeO4](2-)) ion has long been known for its strong oxidizing power and for producing a coagulant from its reduced form (i.e. Fe(III)). However, it has not been studied extensively owing to difficulties with its preparation and its instability in water. This paper describes an improved procedure for preparing solid phase potassium ferrate of high purity (99%) and with a high yield (50-70%). The characteristics of solid potassium ferrate were investigated and from XRD spectra it was found that samples of the solid have a tetrahedral structure with a space group of D-2h (Pnma) and a = 7.705 angstrom, b = 5.863 angstrom, and c = 10.36 angstrom. The aqueous stability of potassium ferrate at various pH values and different concentrations was investigated. It was found that potassium ferrate solution had a maximum stability at pH 9-10 and that ferrate solution at low concentration (0.25 mM) was more stable than at high concentration (0.51 mM). The aqueous reaction of ferrate with bisphenol A (BPA), a known endocrine disrupter compound, was also investigated with a molar ratio of Fe(VI):BPA in the range of 1:1-5:1. The optimal pH for BPA degradation was 9.4, and at this pH and a Fe(VI):BPA molar ratio of 5: 1, approximately 90% of the BPA was degraded after 60 s.
Sanchez-Carretero, A., Saez, C., Canizares, P., Cotillas, S. and Rodrigo, M.A. (2011) Improvements in the Electrochemical Production of Ferrates with Conductive Diamond Anodes Using Goethite as Raw Material and Ultrasound. Industrial & Engineering Chemistry Research 50(11), 7073-7076.

  The improvement in the electrochemical production of ferrates with conductive diamond anodes using goethite as raw material and ultrasounds has been studied. The conductive-diamond electrolysis of suspensions of goethite leads to a higher ferrate concentration than that of Fe(OH)(3) suspensions and of iron-powder bed. With this raw material, the ferrate concentration increases continuously with a constant production rate, after a first more efficient stage in which results are similar to the other two raw materials. In addition, the ferrate production rate is significantly improved in the sonoelectrochemical system, suggesting that the amount of soluble iron ready to be oxidized to ferrates increases with the ultrasound effect. The initial iron concentration only seems to have an influence on the first stage of the process. On the other hand, the concentration of ferrate strongly depends on the hydroxide anion concentration: the higher is the hydroxide concentration, the higher the ferrate concentration is.
Zheng, H.-l., Deng, L.-l., Ji, F.-y., Jiang, S.-j. and Zhang, P. (2010) A New Method for the Preparation of Potassium Ferrate and Spectroscopic Characterization. Spectroscopy and Spectral Analysis 30(10), 2646-2649.
XRD, IR, UV characterization - in Chinese Calcium hypochlorite was used as the raw material for preparation of the high purity potassium ferrate. The study includes the effects of reaction temperature, recrystallization temperature, reaction time, Ca(ClO)(2) dosage, and the amount of calcium hypochlorite on the yield. It was determined that when the reaction temperature was 25 degrees C, recrystallization temperature 0 degrees C and reaction time 40 min, the yield was more than 75%. The purity was detected by direct spectrophotometric method to be more than 92%. The product was characterized by infrared spectrum(IR), X-ray diffraction (XRD) and ultraviolet spectrum (UV) methods and proved to be potassium ferrate that was prepared by calcium hypochlorite as the raw material.
Delaude, L. and Laszlo, P. (1996) A novel oxidizing reagent based on potassium ferrate(VI). Journal of Organic Chemistry 61(18), 6360-6370.
synthetic method used by Strathmann & several Korean groups A new, efficient preparation has been devised for potassium ferrate(VI)(K2FeO4). The ability of this high-valent iron salt for oxidizing organic substrates in nonaqueous media was studied. Using benzyl alcohol as a model, the catalytic activity of a wide range of microporous adsorbents was ascertained. Among numerous solid supports of the aluminosilicate type, the K10 montmorillonite clay was found to be best at achieving quantitative formation of benzaldehyde, without any overoxidation to benzoic acid, The roles of the various parameters (reaction time and temperature, nature of the solvent, method of preparation of the solid reagent) were investigated. The evidence points to a polar reaction mechanism. The ensuing procedure was applied successfully, at room temperature, to oxidation of a series of alcohols to aldehydes and ketones, to oxidative coupling of thiols to disulfides, and to oxidation of nitrogen derivatives. At 75 degrees C, the reagent has the capability of oxidizing both activated and nonactivated hydrocarbons. Toluene is turned into benzyl alcohol (and benzaldehyde), Cycloalkanes are also oxidized, in significant (30-40%) yields, to the respective cycloalkanols (and cycloalkanones). Thus, potassium ferrate, used in conjunction with an appropriate heterogeneous catalyst, is a strong and environmentally friendly oxidant.
Machala, L., R. Zboril, K. Sharma Virender, J. Filip, O. Schneeweiss, J. Madarasz, Z. Homonnay, G. Pokol, and R. Yngard. 2008. Thermal Stability of Solid Ferrates(VI): A Review, p. 124-144, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society.
  This review critically summarizes currently known results concerning the thermal decomposition of the most frequently used ferrate(VI) salts (K2FeO4, BaFeO4, Cs2FeO4). Parameters important in the thermal decomposition of solid ferrates(VI) include the initial purity of the sample, a presence of adsorbed and/or crystal water, reaction atmosphere and temperature, crystallinity, phase transitions, and secondary transformation of the decomposition products. The confirmation and identification of metastable phases formed during thermal treatment can be difficult using standard approach. The in-situ experimental approach is necessary in some cases to understand better the decomposition mechanism. Generally, solid ferrates(VI) were found to be unstable at temperatures above 200 °C as one-step reduction accompanied by oxygen evolution usually proceeds. The most known and used ferrate(VI) salt, potassium ferrate(VI) (K2FeO4), decomposes at high temperatures to potassium orthoferrate(III), (KFeO2), and potassium oxides. The resulting phase composition of the sample heated in air can be affected by accompanying secondary reactions with the participation of CO2 and H2O in air. However, the thermal decomposition of barium ferrate(VI) (BaFeO4) is not sensitive to constituents of air and is mostly reduced to non-stoichiometric BaFeOx(2.5 < x < 3) perovskite-like phases stable under ordinary conditions. Such phases contain iron atoms with oxidation state +4; exhibiting the main difference in the decomposition mechanisms of K2FeO4 and BaFeO4.



Ferrate Analysis
Citation Notes Abstract
Lee, Y., Yoon, J. and von Gunten, U. (2005) Spectrophotometric determination of ferrate (Fe(Vl)) in water by ABTS. Water Research 39(10), 1946-1953.
preferred analytical method for ferrate in treated waters? A new method for the determination of low concentrations (0.03-35 mu M) of the aqueous ferrate (Fe(VI)) was developed. The method is based on the reaction of Fe(VI) with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) which forms a green radical cation (ABTS center dot(+)) that can be measured spectrophotometrically at 415 nm (ABTS method). The reaction of Fe(VI) with ABTS has a stoichiometry of 1:1 in excess of ABTS (73 mu M). The increase in absorbance at 415 nm for ABTS center dot(+) generation was linear with respect to Fe(VI) added (0.03-35 mu M) in buffered solutions (acetate/phosphate buffer at pH = 4.3) and was (3.40 +/- 0.05) x 10(4) M-1 cm(-1). The reaction of Fe(VI) with ABTS was very rapid with a half-life time below 0.01 s at pH 4.3 and 73 mu M of ABTS. This enables the ABTS method to measure Fe(VI) selectively. The residual absorbance of ABTS center dot(+) was found to be stable in several water matrices (synthetic buffer solution and natural waters) and concentrations of Fe(VI) spiked in natural waters could be determined with high accuracy. The ABTS method can also be used as a tool to determine rate constants of reactions of Fe(VI). The second-order rate constant for the reaction of phenol with Fe(VI) was determined to be 90 M-1 s(-1) at pH 7.
Golovko, D.A., Sharma, V.K., Pavlova, O.V., Belyanovskaya, E.A., Golovko, I.D., Suprunovich, V.I. and Zboril, R. (2011) Determination of submillimolar concentration of ferrate(VI) in alkaline solutions by amperometric titration. Central European Journal of Chemistry 9(5), 808-812.   A new amperometric titration method was developed for quantitative determination of ferrate(VI) (Fe(VI)O(4) (2-)) in the 7.06x10(-5)-5.73x10(-3) M concentration range. Chromium(III) hydroxide solution was used as the titrant. The diffusion current (Id) had a linear relationship with the concentration of ferrate(VI) and slopes were dependent on the concentration of NaOH. The amperometric titration could detect a lower concentration of ferrate(VI) than could potentiometric and colorimetric titrations. The method was applied successfully to determine concentrations of ferrate(VI), generated electrochemically, in strong alkaline solutions.
Licht, S., Naschitz, V., Halperin, L., Halperin, N., Lin, L., Chen, J.J., Ghosh, S. and Liu, B. (2001) Analysis of ferrate(VI) compounds and super-iron Fe(VI) battery cathodes: FTIR, ICP, titrimetric, XRD, UV/VIS, and electrochemical characterization. Journal of Power Sources 101(2), 167-176.

cites: 1070 molar absorptivity @505 nm

many other characterization methods

Chemical and electrochemical techniques are presented for the analysis of Fe(VI) compounds used in super-iron electrochemical storage cells. Fe(VI) analytical methodologies summarized are FTIR, ICP, titrimetric, UV/VIS, XRD Fe(VI), potentiometric, galvanostatic, cyclic voltammetry, and constant load, current or power electrochemical discharges probes. The investigated FTIR methodology becomes quantitative with introduction of an internal standard such as added barium sulfate. Electrochemical techniques which utilize a solid cathode, and spectroscopic techniques which utilize a solid sample, are preferred over solution phase techniques. The titrimetric methodology (chromite analysis) has been detailed, and adjusted to determine the extent of Fe(VI --> III) oxidation power in both unmodified or coated Fe(VI) compounds. Fe(VI) compounds have also been variously referred to as ferrates or super-iron compounds, and include K2FeO4 and BaFeO4 Such compounds are highly oxidizing, and in the aqueous phase the full three electron cathodic charge capacity has been realized, as summarized by reactions such as: FeO42- + 5/2H(2)O + 3e(-) --> 1/2Fe(2)O(3) + 5OH(-).
Noorhasan Nadine, N., Sharma Virender, K., Baum, J.C., (2008) A Fluorescence Technique to Determine Low Concentrations of Ferrate(VI), Ferrates, 985, ACS Symposium Series, pp. 145-155. American Chemical Society.   A fluorescence technique to determine low concentrations of aqueous ferrate(VI), [FeVIO42-], in water was developed over a wide pH range using the reaction of ferrate(VI) with scopoletin reagent. The rates of the reaction of ferrate(VI) with scopoletin as a function of pH at 25°C were determined using the stopped-flow technique to demonstrate the reaction is rapid (< 1 min). Spectral measurements on scopoletin at different pH showed that the maximum in absorption varies with the pH while the emission maximum is independent of pH. The absorbance measurements were used to determine the acid dissociation constant, Ka = 1.55 ± 0.01 ? 10-9 (pKa = 8.81 ± 0.05) for scopoletin. The intensity of fluorescence for scopoletin decreases linearly with increase in the concentration of ferrate(VI), which suggests the suitability of the method. Moreover, a relatively large decrease in intensity per micromolar ferrate(VI) concentration was observed, especially at low pH, which makes fluorescence a sensitive technique to determine low ferrate(VI) concentrations.


Ferrate Patents
Citation Notes Abstract
Ciampi & Daly (Feb 17, 2011) Methods of Synthesizing an Oxidant and Applications Thereof, US Patent Application    
Minevski et al. (2005) Electrochemical Method and Apparatus for Producing and Separating Ferrate (VI) Compounds, US Patent 6,946,078 Lynntech Inc, College Station, TX  


Catalytic Ferrate Processes
Citation Notes Abstract
Sharma Virender, K., and V.N. Chenay Benoit. 2008. Heterogeneous Photocatalytic Reduction of Iron(VI): Effect of Ammonia and Formic Acid, p. 350-363, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. Photo-TiO2 Ammonia is a potential pollutant that can contribute to eutrophication of rivers and lakes and its removal is thus becoming an important issue. Formic acid is a byproduct of many industrial processes and its removal from wastewater is of great interest. The removal of ammonia and formic acid was sought by studying the heterogeneous photocatalytic oxidation of ammonia and formic acid in UV-irradiated TiO2 suspensions with and without Fe(VI) (FeVIO42-) at pH 9.0. The kinetics of the reactions was determined by monitoring both reduction of Fe(VI) and oxidation of ammonia/formic acid. The initial rate of Fe(VI) reduction (R) can be expressed as R = kFe(VI)[Fe(VI)]m where m = 1.25 ± 0.03 and 0.70 ± 0.06 for ammonia and formic acid, respectively. The rate constant, kFe(VI), depends on the concentration of ammonia and formic acid. The values of kFe(VI) for the oxidation of ammonia was determined as kFe(VI) = [Ammonia]/(a[Ammonia]+b), a = 6.0 ? 103 µM0.25 s and b = 4.1 ? 106 µM-1.25 s-1. The kFe(VI) for the photocatalytic oxidation of formic acid showed a positive linear relationship, which can be written as kFe(VI) = 2.41 ? 10-3 + 1.58 ? 10-7 ([Formic Acid]). The rates of oxidation of ammonia and formic acid in TiO2/UV suspensions were enhanced in the presence of Fe(VI). Results suggest the photocatalytic production of a highly reactive species, Fe(V), a powerful oxidant, to oxidize ammonia and formic acid. A combination of Fe(VI) and the TiO2 photocatalyst has the potential to enhance the oxidation of pollutants in the aquatic environment.



Other Hyper Oxidized forms of Fe
Citation Notes Abstract
Cabelli Diane, E., and K. Sharma Virender. 2008. Aqueous Ferrate(V) and Ferrate(IV) in Alkaline Medium: Generation and Reactivity, p. 158-166, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. Fe(IV) and Fe(V) This chapter reviews the generation of ferrate(V) and ferrate(IV) complexes in basic solutions. Ferrate(V) (FeVO43-) is easily produced by the one-electron reduction of the relatively stable FeVIO42- ion. Comparatively, generation of a ferrate(IV) complex via one-electron oxidation of Fe(III) is rather difficult, due to the relative insolubility of Fe(III) hydroxides and the slow oxidation rate. This has resulted in limited studies of the reactivity of ferrate(IV). The most studied aquated ferrate(IV) complex is ferrate(IV)-pyrophosphate. The reactivity of ferrate(IV) and ferrate(V) complexes with inorganic and organic substrates in alkaline solution is presented. The reactions of ferrate(IV)-pyrophosphate complex with pyrophosphate complexes of divalent metal ions are likely occurring through inner-sphere electron transfer. Ferrate(V) reacts with substrates predominantly via a two-electron transfer process to Fe(III). The only known example of one-electron reduction of ferrate(V) is its reactivity with cyanide in which sequential reduction of Fe(V) to Fe(IV) to Fe(III) was demonstrated. The reaction of Fe(V) with cyanide thus provides an opportunity for selective and unambiguous production of quantitative amounts of Fe(IV) in aqueous media.
Pestovsky, O., and A. Bakac. 2008. Identification and Characterization of Aqueous Ferryl(IV) Ion, p. 167-176, In V. K. Sharma, ed. Ferrates, Vol. 985. American Chemical Society. Fe(IV) The reaction between ferrous ions and ozone in acidified aqueous solution generates a short-lived species (t½ ≈ 7 sec), which was identified as high-spin pentaaquairon(IV) oxo dication (ferryl) by UV-Vis, Mossbauer, XAS spectroscopies, DFT calculations, 18O isotopic labeling, and conductometric kinetic studies. Kinetic and 18O isotopic labeling studies were used to determine the rate constant for the oxo group exchange between ferryl and solvent water, kex = 1400 s-1. Oxidation of alcohols, aldehydes, and ethers by ferryl occurs by simultaneous hydrogen atom and hydride transfer mechanisms. Ferryl was also found to be an efficient oxygen atom transfer reagent in the reactions with sulfoxides, a water soluble phosphine, and a thiolato-complex of cobalt(III). A quantitative and fast reaction between ferryl and DMSO (kDMSO = 1.3 ? 105 M-1 s-1) produces methyl sulfone. This and some other findings unambiguously rule out ferryl as a Fenton intermediate.



Dissertations and Theses
Citation Notes Abstract
Anquandah, George Aloysius Kofi. "Ferrate(VI) Oxidation of Trimethoprim, Atenolol, Propranolol, Nonylphenol and Octylphenol." Florida Institute of Technology, 2011.   

The kinetic studies of the reactions of Ferrate(VI) (FeO4 2- , Fe(VI)) with these compounds were determined in the acidic to basic pH range at 25°C in order to seek their removal in water. The reactions were first-order with respect to concentrations of both Fe(VI) and compounds, hence the overall reactions followed second-order kinetics. The second-order rate constants were pH dependent. The values were in the ranges of (1.9-0.01)x102 M-1 s-1 , (4.3-12.0)x 100 M-1 s-1 , (1.7-1.4)x101 M -1 s-1 (2.70-0.4)x102 and (3.2 - 0.1)x102 M-1 s-1 for TMP, ATL, PPL, NP, and OP, respectively. The pH dependence was explained by considering the speciation of Fe(VI) and individual compounds. The half-lives of the Fe(VI) oxidation of the compounds ranged from ~ 10 seconds to ~ 30 minutes at pH 7.0 using a 10 mg/L Fe(VI) dose. The stoichiometries of Fe(VI) to TMP or PPL were in molar ratios of 5:1 and 4:1, respectively. Oxidation products of the reactions of Fe(VI) with TMP were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Reaction pathways of oxidation of TMP by Fe(VI) are proposed to demonstrate the cleavage of the TMP molecule to ultimately result in 3,4,5,-trimethoxybenzaldehyde and 2,4-dinitropyrimidine as among the final identified products. The oxidized product mixture exhibited no antibacterial activity against Escherichia coli after complete consumption of TMP. Removal of TMP in the secondary effluent by Fe(VI) was achieved.

Hu, Lanhua. "Oxidative Treatment of Emerging Micropollutants and Viral Pathogens by Potassium Permanganate and Ferrate: Kinetics and Mechanisms." University of Illinois at Urbana-Champaign, 2011.  

Survey tests show that permanganate and ferrate are both selective oxidants that target compounds with specific electron-rich moieties, including olefin, phenol, amine, cyclopropyl, thioether, and alkyne groups. Detailed kinetics studies were undertaken to characterize Mn(VII) oxidation of five representative PhACs that exhibit moderate to high reactivity (carbamazepine, CBZ; ciprofloxacin, CPR; lincomycin, LCM; trimethoprim, TMP; and 17α-ethinylestradiol, EE2), Fe(VI) oxidation of one representative PhAC (CBZ), and Fe(VI) inactivation of MS2 phage (Fe(VI) reactions with other PhACs were not conducted because recent literature reports addressed the topic). The Mn(VII) and Fe(VI) reactions examined with PhAC and MS2 phage were found to follow generalized second-order rate laws, first-order in oxidant concentration and first-order in target contaminant concentration. The temperature dependence of reaction rate constants was found to follow the Arrhenius equation. Changing of solution pH had varying effects on reaction rates, attributed to change in electron density on the target reactive groups upon protonation/deprotonation. The effects of pH on reaction rates were quantitatively described by kinetic models considering parallel reactions between different individual contaminant species and individual oxidant species. For Mn(VII) reactions, removal of PhACs in drinking water utility source waters was generally well predicted by kinetic models that include temperature, KMnO 4 dosage, pH, and source water oxidant demand as input parameters.

A large number of reaction products from Mn(VII) oxidation of CBZ, CPR, LCM, TMP, and EE2 and Fe(VI) oxidation of CBZ were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Structures of reaction products were proposed based on MS spectral data along with information collected from proton nuclear magnetic resonance ( 1 H-NMR), chromatographic retention time, and reported literature on Mn(VII) reactions with specific organic functional groups. Mn(VII) and Fe(VI) rapidly oxidize CBZ by electrophilic attack at the olefinic group on the central heterocyclic ring. Mn(VII) oxidation of CPR was found to occur primary on the tertiary aromatic amine group on the piperazine ring, with minor reactions on the aliphatic amine and the cyclopropyl group. LCM was oxidized by Mn(VII) through the aliphatic amine group on the pyrrolidine ring and thioether group attached to the pyranose ring. TMP oxidation by Mn(VII) was proposed to occur at the C=C bonds on the pyrimidine ring and the bridging methylene group. EE2 oxidation by Mn(VII) resulted in several types of products, including dehydrogenated EE2, hydroxylated EE2, phenolic ring cleavage products, and products with structural modifications on the ethynyl group. Although little mineralization of PhAC solutions was observed after Mn(VII) treatment, results from bioassay tests of three antibiotics show that the antibacterial activity was effectively removed upon reaction with Mn(VII), demonstrating that incomplete oxidation of PhACs during Mn(VII) treatment will likely be sufficient to eliminate the pharmaceutical activity of impacted source waters. Overall, results show that reactions with Mn(VII) likely contribute to the fate of many PhACs in water treatment plants that currently use Mn(VII), and the kinetic model developed in this study can be used to predict the extent of PhAC removal by Mn(VII) treatment. For water contaminated with highly Mn(VII)-reactive PhACs (e.g., carbamazepine, estradiol), specific application of Mn(VII) may be warranted. Results suggest Fe(VI) may be a useful disinfecting agent, but more work is needed to characterize its activity and mode of inactivating with other pathogens of concern.

Yngard, Ria Astrid. "Ferrate(VI) and Ferrate(V) Oxidation of Weak-Acid Dissociable Cyanides." Florida Institute of Technology, 2007.  

Free cyanide and its weak acid dissociable (WAD) metal complexes, generated from different industries, are toxic and must be removed from effluents. This work presents the kinetics and stoichiometry of the oxidation of WAD tetracyano complexes, M(CN) 4 2- (M = Cd, Zn, and Ni) by ferrate (VI) (Fe VI O 4 2- ) and ferrate(V) (Fe VO 4 3- ). The rates of reactions of Fe(VI) with metal WAD cyanides were measured as a function of pH (9.1-10.5) and temperature (15-45°C) by using a stopped-flow technique. The rate laws for the oxidation of M(CN) 4 2- by Fe(VI) may be written as -d[Fe(VI)]/d t = k [Fe(VI)][M(CN) 4 2- ] n where n = 0.5 for Cd 2+ and Zn 2+ and n = 1 for Ni 2+ . The oxidation rates decreased with increase in pH and were primarily related to the reactivity of M(CN) 4 2- with HFeO 4 - . The observed activation energy was determined as 47.8±1.4, 45.7±1.4, and 42.6±1.4 kJ mol -1 for Cd(CN) 4 2- , Zn(CN) 4 2- and Ni(CN) 4 2- , respectively. The stoichiometries of the oxidation of M(CN) 4 2- by Fe(VI) were: 4HFeO 4 - + M(CN) 4 2- + 6H 2 O -> 4Fe(OH) 3 + M 2+ + 4NCO - + O 2 + 4OH - . Except for Ni, metal ions formed in the reaction are subsequently removed from water by possibly iron(III) hydroxide. Mechanisms are proposed that agree with the observed reaction rate-laws and stoichiometries of the oxidation of WAD cyanides by Fe(VI). Overall, results indicate that Fe(VI) can effectively destroy WAD cyanides in effluents.

Rates of reactions of Fe(V) with Cd(CN) 4 2- and Zn(CN) 4 2- were measured at pH 10.0-12.0 using a premix pulse radiolysis technique. Kinetic and spectral studies performed on the reduction of Fe(V) by Cd(CN) 4 2- and Zn(CN) 4 2- suggest two steps in which an intermediate Fe(IV)-cyano complex is formed through a precursor Fe(V)-cyano complex in the first step. In the second step, the intermediate is further converted to Fe(III). If this hypothesis is correct, this is the first example of such aqueous high-valent iron complexes. The rate constant for the oxidation of Cu(CN) 4 3- by Fe(V) was determined at pH 12.0 and 22.0°C as 1.35±0.02 × 10 7 M -1 mol-1 .

Lee, Changyoul. "Oxidation of Humic Substances by Environmentally Friendly Oxidants Iron(VI) and Hydrogen Peroxide." Florida Institute of Technology, 2005.  

The kinetics of the reactions between humic and fulvic acids (HA and FA) and potassium ferrate were investigated under pseudo order conditions. The rates of HA and FA oxidation with ferrate(VI) were determined at pH 9.0, 25°C . The reactions were found to be first order for each reactant. The oxidation of HA and FA with Fe(VI) occurred by two different pathways allowing for two different pseudo first order rate constants. Rate constant values for an estuarine FA (Mullet Creek) were very similar to those for SRFA (Suwannee River Fulvic Acid) increasing the likelihood that the values are applicable to other natural aqueous systems. The degradation of HA and FA in aqueous solution by means of a photolytic method was also studied. Both FA and HA oxidation by H 2 O2 followed first-order kinetics for HS (humic substances) and fractional order kinetics for H2 O 2 , respectively. The optimum H2 O2 dose was found to be 86 mM for the oxidation of HS from this study. The oxidation efficiency of Fe(VI) and oxidation by-products were analyzed by TOC, NMR and GC/MS. The TOC experiments were conducted by measuring organic carbon contents after the oxidation of FA. The results showed that the oxidation of HS by Fe(VI) occurred efficiently and led to 48% mineralization within 30min. The NMR results showed a decrease in aromaticity and carbohydrates after oxidation, and the GC/MS analysis positively identified small carboxylic acid and polycarboxylic acid residues. The heterogeneous photocatalytic degradation of FA and HA by Fe(VI) with UV/TiO2 was investigated at pH 9.0, 25°C . The oxidation of HS by the Fe(VI) was enhanced by the addition of TiO 2 in the presence of UV light.

Dormedy, Derek Frank. "I. Kinetics and Mechanism of the Ferrate Oxidation of Dimethyl Sulfide in Aqueous Solution. II. A Temporal Profile of Triazine and Acetanilide Herbicides in Surface and Ground Water Near Ashland, Nebraska." The University of Nebraska - Lincoln, 2000.  

I . This work studies the reaction of ferrate with dimethyl sulfide (DMS). Reactants, intermediates, and products of this reaction were measured in a mechanistic study of this reaction. The source and destination of the oxygen atoms involved in this aqueous reaction were tracked using 18 O-labeled water. This was accomplished by monitoring the masses of dimethyl sulfoxide (DMSO and DMS18 O) by GC-MS. Information concerning intermediates was obtained by quenching the reaction at various times with hydroxylamine. The effect of different buffers and dissolved oxygen on the reaction were studied at pH 10.2 and found to have no significant influence on the kinetics or product distribution. Resolved rate constants were calculated to be 11sec-1 and 426sec-1 respectively for FeO42- and HFeO4- reacting with DMS.

Isotope tracers using 18 O-labeled water, GC-MS detection of the products and oxygen quantitation were used to provide evidence for an oxygen atom transfer from Fe(VI) to DMS being a step in the mechanism. It was also found that some solvent oxygen was incorporated into DMSO, probably from hydrogen peroxide or hydroxyl radical formed by oxidation of water by ferrate.

II . Atrazine, cyanazine, alachlor, acetachlor and metolachlor were detected in the Platte River and surrounding ground water after the first thunderstorm following herbicide application. Maximum concentrations of atrazine in the Platte River vary from 2 ppb to 12 ppb in the years 1995 through 1998. Many tributaries intersect with the Platte River, but mixing of these waters is incomplete even miles downstream from their convergence. Induced recharge pulls surface water that may be contaminated with herbicides into the drinking water aquifer. Concentrations of analytes in the ground water near the Platte River in eastern Nebraska can be between 0 and 100% of the surface water concentrations.

The lag time of this process has been estimated for wells at different distances from the Platte River. The lag times for analytes to enter production wells on an island in the river were between 5 and 9 days and to enter a monitoring well on the mainland were between 11 to 21 days. Because of these differences in lag times, analytes that degraded faster (acetanilides) were rarely detected in water samples taken from the mainland. Water samples taken from island wells regularly contained detectable concentrations of an the analytes.

Hornstein, Brooks John. "Reaction Mechanisms of Hypervalent Iron: The Oxidation of Amines and Hydroxylamines by Potassium Ferrate." New Mexico State University, 1999.   

The reaction kinetics of aniline, hydroxylamine, N-methylaniline and benzylamine with potassium ferrate have been studied. For each oxidation there is evidence for the formation of an iron-substrate intermediate that is subject to different fates depending on the reaction conditions. The lifetime of the reactive intermediate is dependent upon the nature of the substrate and in some situations these intermediates are observed spectrally. This work not only provides information about the oxidation mechanisms associated with ferrate but also lends insight into the development of new high oxidation state iron compounds.

Gai, Huifa. "A Kinetic Study of the Reduction of Ferrate by Water and the Oxidation of Alcohols by Ferrate." The University of Regina (Canada), 1996.  

The kinetics of the reduction of potassium ferrate by water have been investigated. When the pH is lower than 8 the reaction is second order with respect to tetraoxoferrate(VI) ion. When the pH is higher than 10 the reaction is first order with respect to ferrate ion. A mixed order is found between pH 8 and 10. Ferrate ion is kinetically most stable at a pH of approximately 9.5.

The kinetics of the oxidation of 2-propanol and mandelic acid have been studied. The rate laws for the oxidation of these alcohols are first order in alcohol are first order in ferrate ion. The small influence of the ionic strength on the reaction rate suggests that there is no significant charge build up in the transition state. The determination of a primary deuterium isotope effect and the observation that the rates for the oxidation of ethers and alcohols are comparable suggest that the reaction is initiated by reaction of the $\alpha$-C-H bond with ferrate ion. Open chain products observed from the oxidation of cyclobutanol indicate generation of free radicals during the reaction. Mechanisms consistent with these observations are considered. The oxidation of alcohols, alkenes and other substrates by ferrate under heterogenous conditions has also been investigated. The products of the oxidation of secondary alcohols are the corresponding ketones. The products of the oxidation of primary alcohols are the corresponding aldehydes or aldehydes with one or more less carbons. The products of the oxidation of double bonds are the corresponding aldehydes or ketones. There is no significant selectivity for oxidation of double bonds or hydroxyl functional groups in the system investigated. The usefulness of this reaction for organic synthesis is evaluated.

Erickson, John Edward. "The Oxidation of Water and Inorganic Nitrogen Compounds by Potassium Ferrate (VI)." The University of Nebraska - Lincoln, 1988.  

The oxidations of azide, hydroxylamine, hydrazine, and ammonia by potassium ferrate(VI) were investigated in aqueous solutions from neutral to basic pH conditions. The study included both reaction kinetics and product determination. The rate of disappearance of the ferrate(VI) ion was monitored spectrophotometrically at 505 nm using both stopped-flow and conventional instruments. The analytical techniques of gas chromatography, ion chromatography, and differential pulse polarography were used to identify and quantitate the products of these reactions. Dinitrogen, nitrous oxide, nitrite, and nitrate were the most often encountered nitrogen-containing products from these oxidations. A mass balance between the products formed and the ferrate(VI) reacted was calculated for each reductant. Based on the kinetic results and the product analysis data, the order of reactivity of these solutes toward ferrate(VI) at pH 10 is: N$\sb2$H$\sb4$ $>$ NH$\sb2$OH $\gg$ NH$\sb3$ $>$ N$\sb3\sp-$. At pH 7, the reactivity order is: N$\sb2$H$\sb5\sp+$ $>$ NH$\sb2$OH $\approx$ N$\sb3\sp-$ $\gg$ NH$\sb4\sp+$. A mechanism is proposed for each of these reactions which is consistent with the kinetic data and the product distributions. The reactive species nitroxyl (HNO or NO$\sp-$) is suggested as a likely intermediate in a number of the proposed mechanisms. In addition, the stoichiometry and products from the oxidation of solvent water by the ferrate(VI) in the pH range from 4 to 8.5 was reinvestigated. Gas chromatography and differential pulse polarography were used to determine the products of the reaction. Molecular oxygen is found to be the major product of this oxidation with small amounts of hydrogen peroxide also detected. A mechanism has been proposed by which these products are formed.

McLaughlin, Charles William. "OXIDATION OF NITRITE IONS AND CHLORINE-CONTAINING COMPOUNDS BY POTASSIUM FERRATE(VI)." The University of Nebraska - Lincoln, 1984. oxidation of hypochlorite to chlorite and chlorate

Potassium ferrate(VI) was shown to easily oxidize aqueous nitrite ions to nitrate over the pH range of 2.5 to 6.8. Stopped-flow and conventional spectroscopy were used to monitor the rate of disappearance of the purple solution color of potassium ferrate(VI) at 505nm. The parallel oxidation of solvent water was also monitored using a calibrated dissolved oxygen probe. A selective nitrate electrode was used to potentiometrically determine product formation. The overall reaction was determined to be mixed-order with a hydronium ion dependency of 0.58. The rate of the reaction was also shown to depend on the fraction of species of diprotonated ferrate(VI). Potassium ferrate(VI) was also able to oxidize chlorite ions to chlorate and hypochlorite to chlorite. Evidence is also presented showing, to a slight extent, the oxidation of chlorate to perchlorate. Attempts were made to oxidize chloride to higher states, but no successful oxidation was detected. Chlorate oxidation rates were studied at pH's from 2.5 to 6.8. Chlorite rates were determined from pH 8.0 to 10.1. Hypochlorite oxidation was investigated over the pH range 6.4 to 8.4. Possible chloride oxidation was investigated from a pH of 3.5 to 8.2. Identification of possible solute oxidation products was accomplished via ion chromatography of stock solutions that had been reacted with potassium ferrate(VI). The parallel oxidation of solvent water to oxygen was also monitored with a dissolved oxygen probe. Investigation of chlorate containing solutions showed the water oxidation pathway of potassium ferrate(VI) to be much more favorable than the chlorate oxidation pathway. The same result was obtained when chloride was in solution. However, when chlorite was in solution, the solvent oxidation pathway was less favored. The rate of water oxidation was shown to be inversely related to chlorite concentration. When hypochlorite was in solution with potassium ferrate(VI) the amount of water being oxidized increased with increased hypochlorite. This was explained by the oxidation of hypochlorite to chlorite with a subsequent reaction that produces chlorine dioxide.

Bartzatt, Ronald Lee. "THE KINETICS OF OXIDATION OF VARIOUS ORGANIC SUBSTRATES BY POTASSIUM FERRATE." The University of Nebraska - Lincoln, 1982.   

The ferrate oxidation of diethylsulfide and 2,2-thiodiethanol were studied in a pH range of 8.90 to 9.90. The ferrate oxidation of chloral was studied in a pH range of 7.90 to 9.30. Chloral exists in aqueous solution in its hydrated form. The oxidation of acetaldehyde by potassium ferrate has been studied at three different temperatures. Neopentyl alcohol has been studied at three different x temperatures. An increase in reaction temperature does not bring about an increase in k(,1(Obs)). Using the data obtained for acetaldehyde, observations concerning thermodynamics can be made. Calculations for activation energy, A study of water oxidation by potassium ferrate was made. The values of k(,1(Obs)) for water oxidation by potassium ferrate do not change significantly as temperature of the reaction solutions vary from 35C to 18C. Graphs of Log k(,1(Obs)) versus pH and Log k(,2(Obs)) versus pH are linear.


The aqueous solutions for five organic "priority pollutants" were selected for oxidation and coagulation studies by use of potassium ferrate. Naphthalene and Trichloroethylene were successfully removed from waste streams with proper pH control. Nitrobenzene was oxidized very slowly by ferrate. Bromodichloromethane and 1,2-dichlorobenzene were not removed from aqueous streams under the oxidation test conditions. The Ames test results indicate that the potassium ferrate treatment did not produce products that were detectable by the Ames test as mutagenic.

A comparative study of the efficiency of removal of organic pollutants by coagulation with ferrate and alum was conducted using Jar test. Potassium ferrate oxidation-coagulation is not a satisfactory process for removal of Nitrobenzene, 1,2-dichlorobenzene and Bromodichloromethane. Ferrate by itself does not form a floc surface on which the priority pollutants might be sorbed. It is necessary to provide a coagulant aid. Alum coagulation is not a satisfactory process for removal of those pollutants either. The efficiency of ferrate and alum using paddles versus gas (N(,2)) in the flocculation process was compared. The removal efficiencies of Naphthalene, Trichloroethylene, Bromodichloromethane and 1,2-dichlorobenzene were higher than those obtained using paddles. However, it is the stripping which accounts for the removal of the volatile compounds which cannot be effectively removed by either ferrate or Alum.


It was found that many factors can effect the observed rate constants of the oxidation of organic substrates by the ferrate (VI) ion. Selection of buffer will either increase or decrease or decrease the observed rate constants, depending upon the buffer chosen. Increasing the total ionic strength will increase the observed rate constants, while the effect of changing the initial potassium ferrate concentration is not altogether clear. The presence of Fe(III) generated from the reduction of Fe(VI) in solution enhances the rate of oxidation, while adding Fe(III) to the unreacted solution does not affect the oxidation rate. Dual-wavelength spectroscopy was used to try and eliminate any effect in the calculated rate constants due to absorption or scattering of light by the Fe(III) product. It was found that the results were identical to those found when using a single wavelength, dual beam spectrophotometer. The kinetics of the oxidation of water by ferrate (VI) were examined in the pH range of 4.80 to 7.78. The data were shown to fit a mixed-order kinetic model. The second-order process was by far the largest contribution to the rate. As a result, the second-order rate constants showed a much clearer trend than the corresponding first-order rate constants. The reactions showed a strong pH dependence. The half-lives of the reactions ranged from about 100 msec at pH 4.80 to about 50 sec at pH 7.78. The results from the higher pH range (7.5 and above) were in good agreement with those obtained by other workers. The kinetics and the products of the reaction of nitrilotriacetic acid and ferrate (VI) were examined.

Tabatabai, Ali Reza. "OXIDATION KINETICS OF ORGANIC MOLECULES BY POTASSIUM FERRATE (VI)." The University of Nebraska - Lincoln, 1980.  

The decomposition of potassium ferrate (VI) was studied in the pH range of 8.35 to 9.58. The rate expression was found to be mixed-first- and second-order, in which the second-order rate constant was the major component of the rate. The effects of the initial concentration of potassium ferrate (VI), products of the decomposition, impurities of the potassium ferrate (VI) and the buffer system were found to be minor on the second-order rate constant. However, these variables had a major effect on the first-order rate constant. The method of initial rates applied to the decomposition reactions of ferrate (VI) also implied a mixed-first and -second-order rate expression for the initial decomposition of ferrate (VI). The effect of addition of ferrate (IV) on the rate of decomposition of ferrate (VI) was found to be minor. The oxidation kinetics of formic acid, formaldehyde, and methanol by potassium ferrate (VI) in phosphate-borate buffer in the pH range of 8 to 10 was studied. The oxidation rate constants including a 0.6 order dependence on hydrogen ion for those substrates were determined to be as follows: 10('-4) k(,s) (1/M('1.6) sec), HCOO('-) 2.99, HCHO 9.6, CH(,3)OH 0.65

Chow, Victor Shui-Chiu. "Preparation and Spectroscopic Examination of Potassium Ferrate." Stephen F. Austin State University, 1974.    
Haire, R. G. (1965). A Study of the Decomposition of Potassium Ferrate (VI) in Aqueous Solution: start-pg.28, pg.29-pg.123, pg.124-165, pg.166-end. MSU Dissertation, Dept of Chem  
Magee, J. S. Jr. (1961). The Kinetics of the Decomposition of Potassium Tetraoxoferrate (VI) in Aqueous Solution, University of Delaware mechanism cited by Haire