Revisiting the Electron Transfer Mechanisms in Ru(III)-Mediated Advanced Oxidation Processes with Peroxyacids and Ferrate(VI).

The potential of Ru(III)-mediated advanced oxidation processes has attracted attention due to the recyclable catalysis, high efficiency at circumneutral pHs, and robust resistance against background anions (e.g., phosphate). However, the reactive species in Ru(III)-peracetic acid (PAA) and Ru(III)-ferrate(VI) (FeO42-) systems have not been rigorously examined and were tentatively attributed to organic radicals (CH3C(O)O•/CH3C(O)OO•) and Fe(IV)/Ru(V), representing single electron transfer (SET) and double electron transfer (DET) mechanisms, respectively. Herein, the reaction mechanisms of both systems were investigated by chemical probes, stoichiometry, and electrochemical analysis, revealing different reaction pathways. The negligible contribution of hydroxyl (HO•) and organic (CH3C(O)O•/CH3C(O)OO•) radicals in the Ru(III)-PAA system clearly indicated a DET reaction via oxygen atom transfer (OAT) that produces Ru(V) as the only reactive species. Further, the Ru(III)-performic acid (PFA) system exhibited a similar OAT oxidation mechanism and efficiency. In contrast, the 1:2 stoichiometry and negligible Fe(IV) formation suggested the SET reaction between Ru(III) and ferrate(VI), generating Ru(IV), Ru(V), and Fe(V) as reactive species for micropollutant abatement. Despite the slower oxidation rate constant (kinetically modeled), Ru(V) could contribute comparably as Fe(V) to oxidation due to its higher steady-state concentration. These reaction mechanisms are distinctly different from the previous studies and provide new mechanistic insights into Ru chemistry and Ru(III)-based AOPs.

Ferrate as a coagulant prior to sand filters treating secondary wastewater effluent for reuse.

Wastewater reuse is one of the crucial water resources in Egypt due to the ongoing need to increase water resources and close the supply-demand gap. In this study, a new coagulant has been investigated before sand filters as an advanced wastewater treatment method. The sand filter pilot was run at a hydraulic loading rate of 0.75 m/h and two different dosages of three coagulants (Alum, FeCl3, and Ferrate VI) were selected using the jar tests. The sand filter without coagulant removed 12% of BOD5 and 70% of turbidity. Applying in-line coagulation before the sand filter provided effluents with better quality, especially for turbidity, organics, and microorganisms. Ferrate provided the highest removal of turbidity (90%) and BOD5 (93%) at very low dosages and lower costs compared with other coagulants, however, it adversely impacted both conductivity and dissolved solids. A significant effect on reducing bacteria was obtained with 40.0 mg/L of alum. According to the study's findings, the ferrate coagulant enhanced the sand filter's performance producing effluents with high quality, enabling it to meet strict water reuse regulations as well as aquatic environmental and health preservations.

Promoting Effect of Silver Oxide Nanoparticles on the Oxidation of Bisphenol B by Ferrate(VI).

Bisphenol B (BPB, 2,2-bis(4-hydroxyphenyl) butane), as a substitute for bisphenol A, has been widely detected in the environment and become a potential threat to environmental health. This work found that silver oxide nanoparticles (Ag2O) could greatly promote the removal of BPB by ferrate (Fe(VI)). With the presence of 463 mg/L Ag2O, the amount of Fe(VI) required for the complete removal of 10 µM BPB will be reduced by 70%. Meanwhile, the recyclability and stability of Ag2O have been verified by recycling experiments. The characterization results and in situ electrochemical analyses showed that Ag(II) was produced from Ag(I) in the Fe(VI)-Ag2O system, which has a higher electrode potential to oxidize BPB to enhance its removal. A total of 13 intermediates were identified by high-resolution mass spectrometry, and three main reaction pathways were proposed, including oxygen transfer, bond breaking, and polymerization. Based on the toxicity assessment through the ECOSAR program, it is considered that the presence of Ag2O reduced the toxicity of BPB oxidation intermediates to aquatic organisms. These results would deepen our understanding of the interaction between Fe(VI) and Ag2O, which may provide an efficient and environmentally friendly method for water and wastewater treatment.

A Comparative Study on the Oxidation Mechanisms of Substituted Phenolic Pollutants by Ferrate(VI) through Experiments and Density Functional Theory Calculations.

In this work, the oxidation of five phenolic contaminants by ferrate(VI) was comparatively investigated to explore the possible reaction mechanisms by combined experimental results and theoretical calculations. The second-order rate constants were positively correlated with the energy of the highest occupied molecular orbital. Considering electronic effects of different substituents, the easy oxidation of phenols by ferrate(VI) could be ranked as the electron-donating group (-R) > weak electron-withdrawing group (-X) > strong electron-withdrawing group (-(C═O)-). The contributions of reactive species (Fe(VI), Fe(V)/(IV), and •OH) were determined, and Fe(VI) was found to dominate the reaction process. Four main reaction mechanisms including single-oxygen transfer (SOT), double-oxygen transfer (DOT), •OH attack, and electron-transfer-mediated coupling reaction were proposed for the ferrate(VI) oxidation process. According to density functional theory calculation results, the presence of -(C═O)- was more conducive for the occurrence of DOT and •OH attack reactions than -R and -X, while the tendency of SOT for different substituents was -R > -(C═O)- > -X and that of e--transfer reaction was -R > -X > -(C═O)-. Moreover, the DOT pathway was found in the oxidation of all four substituted phenols, indicating that it may be a common reaction mechanism during the ferrate(VI) oxidation of phenolic compounds.

Enhancing Ferrate Oxidation of Micropollutants via Inducing Fe(V)/Fe(IV) Formation Needs Caution: Increased Conversion of Bromide to Bromate.

This study explores the formation of bromate (BrO3-) in the copresence of Fe(VI) and bromide (Br-). It challenges previous beliefs about the role of Fe(VI) as a green oxidant and highlights the crucial role of intermediates Fe(V) and Fe(IV) in the conversion of Br- to BrO3-. The results show that the maximum concentration of BrO3- of 48.3 µg/L was obtained at 16 mg/L Br- and that the contribution of Fe(V)/Fe(IV) to the conversion was positively related to pH. The study suggests that a single-electron transfer from Br- to Fe(V)/Fe(IV) along with the generation of reactive bromine radicals is the first step of Br- conversion, followed by the formation of OBr- which was then oxidized to BrO3- by Fe(VI) and Fe(V)/Fe(IV). Some common background water constituents (e.g., DOM, HCO3-, and Cl-) significantly inhibited BrO3- formation by consuming Fe(V)/Fe(IV) and/or scavenging the reactive bromine species. While investigations proposing to promote Fe(V)/Fe(IV) formation in Fe(VI)-based oxidation to enhance its oxidation capacity have been rapidly accumulated recently, this work called attention to the considerable formation of BrO3- in this process.

Peracetic Acid Enhances Micropollutant Degradation by Ferrate(VI) through Promotion of Electron Transfer Efficiency.

Ferrate(VI) and peracetic acid (PAA) are two oxidants of growing importance in water treatment. Recently, our group found that simultaneous application of ferrate(VI) and PAA led to much faster degradation of micropollutants compared to that by a single oxidant, and this paper systematically evaluated the underlying mechanisms. First, we used benzoic acid and methyl phenyl sulfoxide as probe compounds and concluded that Fe(IV)/Fe(V) was the main reactive species, while organic radicals [CH3C(O)O•/CH3C(O)OO•] had negligible contribution. Second, we removed the coexistent hydrogen peroxide (H2O2) in PAA stock solution with free chlorine and, to our surprise, found the second-order reaction rate constant between ferrate(VI) and PAA to be only about 1.44 ± 0.12 M-1s-1 while that of H2O2 was as high as (2.01 ± 0.12) × 101 M-1s-1 at pH 9.0. Finally, further experiments on ferrate(VI)-bisulfite and ferrate(VI)-2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic)acid systems confirmed that PAA was not an activator for ferrate(VI). Rather, PAA could enhance the oxidation capacity of Fe(IV)/Fe(V), making their oxidation outcompete self-decay. This study, for the first time, reveals the ability of PAA to promote electron transfer efficiency between high-valent metals and organic contaminants and confirms the benefits of co-application of ferrate(VI) and PAA for alkaline wastewater treatment.

On the Origins of Some Spectroscopic Properties of "Purple Iron" (the Tetraoxoferrate(VI) Ion) and Its Pourbaix Safe-Space.

In this work, the authors attempt to interpret the visible, infrared and Raman spectra of ferrate(VI) by means of theoretical physical-inorganic chemistry and historical highlights in this field of interest. In addition, the sacrificial decomposition of ferrate(VI) during water treatment will also be discussed together with a brief mention of how Rayleigh scattering caused by the decomposition of FeVIO42- may render absorbance readings erroneous. This work is not a compendium of all the instrumental methods of analysis which have been deployed to identify ferrate(VI) or to study its plethora of reactions, but mention will be made of the relevant techniques (e.g., Mössbauer Spectroscopy amongst others) which support and advance this overall discourse at appropriate junctures, without undue elaboration on the foundational physics of these techniques.

Oxidative degradation of chlorpyrifos using ferrate(VI): Kinetics and reaction mechanism.

In this study, we investigated the degradation kinetics of chlorpyrifos, an organophosphorus (OP) compound, using ferrate(VI), and investigated the potential of this iron-based chemical oxidant on chlorpyrifos removal from water and wastewater treatments. A series of kinetic experiments were conducted to evaluate the influence of various environmental factors, such as pH, oxidant dosages, as well as the presence of anions, cations, humic acid (HA), and different water matrices. Chlorpyrifos was completely removed within 300 s under the following optimum conditions: [chlorpyrifos]0 = 1 µM, [Fe(VI)]0:[chlorpyrifos]0 = 100:1, T = 25 °C, and pH = 7.0. Anions such as Cl-, SO42-, NO3-, and HCO3- and cations such as Fe3+, Cu2+, and NH4+ did not appear to influence the removal of chlorpyrifos. However, the presence of Ca2+, Mg2+, and HA in water inhibited the degradation of chlorpyrifos. Experiments on removing chlorpyrifos from tap water, river water, and synthetic wastewater were performed to demonstrate the practical applications of Fe(VI). Ten oxidation products of chlorpyrifos were identified using liquid chromatography-quadrupole-time-of flight-mass spectrometry (LC-Q-TOF-MS), and their structures were further elucidated using MS/MS spectra. Then, two degradation pathways were preliminarily proposed including the oxidation of the P = S bond, cleavage of C-O bond, and hydroxyl substitution reaction. In general, Fe(VI) could be used as an efficient technology for chlorpyrifos removal from water and wastewater treatments.

Green Ferrate(VI) for Multiple Treatments of Fracturing Wastewater: Demulsification, Visbreaking, and Chemical Oxygen Demand Removal.

Fracturing wastewater is often highly emulsified, viscous, and has a high chemical oxygen demand (COD), which makes it difficult to treat and recycle. Ferrate(VI) is a green oxidant that has a high redox potential and has been adopted for the efficient oxidation of fracturing wastewater to achieve triple effects: demulsification, visbreaking, and COD removal. Firstly, optimal conditions were identified to build a model for fast and efficient treatment. Secondly, wastewater treatment using ferrate oxidation was investigated via demulsification, visbreaking, and COD removal. Finally, a mechanism for ferrate oxidation was proposed for the three effects using Fourier-transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The theoretical and experimental data demonstrated that the ferrate oxidation achieved the three desired effects. When ferrate was added, the demulsification efficiency increased from 56.2% to 91.8%, the total viscosity dropped from 1.45 cp to 1.10 cp, and the total removal rate of COD significantly increased to 74.2%. A mechanistic analysis showed that the strongly-oxidizing ferrate easily and efficiently oxidized the O/W interfacial film materials, viscous polymers, and compounds responsible for the COD, which was a promising result for the triple effects.

Enhancing ferrate(VI) oxidation process to remove blue 203 from wastewater utilizing MgO nanoparticles.

The aim of this study is to investigate the beneficial effect of utilizing MgO nanoparticles on the performance of ferrate(VI) oxidation process to remove blue-203 dye from wastewater. It was also made an attempt to assess the effects of pH, temperature, and MgO nanoparticle dosage on this oxidation process performance. Several sets of batch experiment were conducted to find out the effects of temperature ranging from 25 to 65 °C, pH ranging from 1.5 to 13, ferrate(VI) concentration ranging from 0.5 to 5.9 mg/L and MgO nanoparticles dosage ranging from 0.01 to 0.05 g in 150 mL solution on the removal efficiency. The results showed that adding MgO nanoparticles can improve the performance of ferrate(VI) oxidation removal method significantly, spec. at basic conditions. This synergistic effect can be attributed to the simultaneous adsorption of ferrate(VI) and dye molecules on the surface of nanoparticles. The results also revealed that the reaction between blue-203 dye and ferrate(VI) takes place rapidly at high mixing rate. It means that the required time to complete the removal process is controlled by mixing rate. It was finally concluded that adding MgO nanoparticles was an efficient means to enhance the performance of ferrate(VI) to oxidize blue-203 dye, esp. under basic conditions.

The role of mixing in potassium ferrate(VI) consumption kinetics and disinfection of bypass wastewater.

Bypass wastewaters need an appropriate auxiliary treatment to address their broad range of chemical and bacterial characteristics. The dual capacity of potassium ferrate(VI) as disinfectant/oxidant and coagulant may be useful in a sustainable process retrofit to provide adequate treatment to such wastewaters. However, the engineering aspects of potassium ferrate(VI) based technology to retrofit within existing coagulation-flocculation-sedimentation basins have not been studied. This study investigated, for the first time, the role of rapid mixing on the rate of potassium ferrate(VI) decay and disinfection in bypass wastewaters from extreme wet weather flow events. First-order, second-order, and double exponential models were fit to the potassium ferrate(VI) consumption data, and the double exponential model was able to represent the potassium ferrate(VI) decay in all conditions with a high coefficient of determination and low mean square error. In addition, Chick-Watson and Hom models were tested in this study, and both fit the E. coli disinfection results. The rates of potassium ferrate(VI) consumption and disinfection derived from the models were higher using 500-1000 rpm rapid mixing speeds than they were when magnetic stirrer mixing was used for the same initial dosage and wastewater sample. There was no significant increase in the potassium ferrate(VI) consumption or disinfection rates with the increase of the rapid mixing speeds from 500 to 1000 rpm which revealed that the reactions were kinetically controlled. The coagulation capability of potassium ferrate(VI) enhanced the sedimentation ability and contributed almost the same as the chemical disinfection capability to the overall E. coli removal. This study suggests that potassium ferrate(VI) can be implemented in existing facilities that mix coagulants to enhance primary sedimentation, yet potassium ferrate(VI) can provide both disinfection and coagulation at lower mixing speeds.

Oxidation of propyl paraben by ferrate(VI): Kinetics, products, and toxicity assessment.

Propyl paraben (propyl 4-hydroxybenzoate, PPB), one of the typically used paraben species in various pharmaceutical and personal care products, has been found in different aquatic environment, which could affect the water quality and human health. In this paper, the degradation of PPB by aqueous ferrate (Fe(VI)) was investigated in different water matrix and reaction kinetics as a function of pH was determined. Intermediate products of the degradation process were isolated and characterized by the high performance liquid chromatography/mass spectrometry/mass spectrometry techniques. Acute and chronic toxicities during water treatment of PPB using Fe(VI) were calculated using the ECOSAR program at three trophic levels. The obtained apparent second-order rate constant (kapp) for PPB reaction with Fe(VI) ranged from 99.6 ± 0.4 M-1 s-1 to 15.0 ± 0.1 M-1 s-1 with the half-life (t1/2) ranging from 154 s to 1026 s at pH 6.5-10.0 for an Fe(VI) concentration of 600 µM. The proposed pathway for the oxidation of PPB by Fe(VI) involves one electron transfer of phenoxyl radical and breaking of the ether bond. In general, the oxidation of PPB by ferrate resulted in a significant decrease in toxicity at three trophic levels.

Degradation of sulfonamides and formation of trihalomethanes by chlorination after pre-oxidation with Fe(VI).

Sulfonamides are used in human therapy, animal husbandry and agriculture but are not easily biodegradable, and are often detected in surface water. Sulfamethazine (SMZ) and sulfadiazine (SDZ) are two widely used sulfonamide antibiotics that are used heavily in agriculture. In this study, they were degraded in an aqueous system by chlorination after pre-oxidation with ferrate(VI) (FeVIO42-, Fe(VI)), an environmentally friendly oxidation technique that has been shown to be effective in degrading various organics. The kinetics of the degradation were determined as a function of Fe(VI) (0-1.5mg/L), free chlorine (0-1.8mg/L) and temperature (15-35°C). According to the experimental results, SMZ chlorination followed second-order kinetics with increasing Fe(VI) dosage, and the effect of the initial free chlorine concentration on the reaction kinetics with pre-oxidation by Fe(VI) fitted a pseudo-first order model. The rate constants of SDZ and SMZ chlorination at different temperatures were related to the Arrhenius equation. Fe(VI) could reduce the levels of THMs formed and the toxicity of the sulfonamide degradation systems with Fe(VI) doses of 0.5-1.5mg/L, which provides a reference for ensuring water quality in drinking water systems.

Formaldehyde removal from wastewater and air by using UV, ferrate(VI) and UV/ferrate(VI).

Formaldehyde removal from an air stream absorbed into a water stream in a packed bed continuously and then removed by employing a combination of UV and ferrate(VI) as a highly-powerful oxidant in a continuous stirred tank. In addition, the removal of formaldehyde from water was investigated in both batch and continuous modes. The results of the study performed on formaldehyde-contaminated water treatment can be used for both air and water treatment process design. The primary objective of this study is to compare the performance of using UV and ferrate(VI) individually with that of using UV/ferrate(VI) simultaneously to remove formaldehyde from both air and water. Moreover, the effects of several factors such as pH, ferrate(VI) concentration and temperature on formaldehyde removal from water using ferrate(VI) method were evaluated. The results of the current study in batch condition showed that the best initial pH and ferrate(VI) concentration to obtain the highest formaldehyde removal are 2 and 1 mg/l, respectively. The results of this part of research also reveal that temperatures rise from 25 °C to 50 °C increases formaldehyde removal from 69% to 97%; however, further increase in temperature has an adverse effect on removal efficiency. The combination of UV and ferrate(VI) enhances formaldehyde removal efficiency to very close to 100% within 35 min. In continuous air stream treatment, maximum formaldehyde removal of 94% was obtained by using a packed bed scrubber with gas over liquid flow rates ratio of 1.28 m3/m3. Although the results of this study shows that ferrate(VI) method for removal of formaldehyde can be considered as a promising alternative for both water and air treatment, further economic studies are required for this process to be commercialized.

Synthesis of Graphene Oxide by Oxidation of Graphite with Ferrate(VI) Compounds: Myth or Reality?

It is well established that graphene oxide can be prepared by the oxidation of graphite using permanganate or chlorate in an acidic environment. Recently, however, the synthesis of graphene oxide using potassium ferrate(VI) ions has been reported. Herein, we critically replicate and evaluate this new ferrate(VI) oxidation method. In addition, we test the use of potassium ferrate(VI) for the synthesis of graphene oxide under various experimental routes. The synthesized materials are analyzed by a number of analytical methods in order to confirm or disprove the possibility of synthesizing graphene oxide by the ferrate(VI) oxidation route. Our results confirm the unsuitability of using ferrate(VI) for the oxidation of graphite on graphene oxide because of its high instability in an acidic environment and low oxidation power in neutral and alkaline environments.

A new perspective on contaminants as "activators": Aromatic amine groups promoted degradation of tetracycline by ferrate(VI).

Occasionally, our group found that the degradation of tetracycline by ferrate(VI) could be promoted by four co-exist contaminants, containing aromatic amines (ofloxacin, diatrizoic acid, sulfadiazine and alachlor). This study investigated the promotion of aromatic amine groups on tetracycline degradation by ferrate(VI) by using aniline as a model compound. The results implied that the presence of aniline increased the degradation rate of tetracycline by 2.76 times, and the enhancement was weakened gradually with the decrease of pH from 10 to 7.5. The generation of Fe(IV) and·OH by the reaction between ferrate(VI) and aniline was proposed to enhance the degradation of tetracycline, supported by quenching experiments, electron paramagnetic resonance (EPR) and theoretical calculations. A positive correlation was found between the rate constant of tetracycline degradation and the electron-donating ability of the substituted amines (quantified by the Hammett substituent constants). In addition, the degradation of tetracycline was remarkably inhibited by HA and some inorganic ions such as NO3-, SO42-, Cl-, Ca2+, and Mg2+, and the inhibition also happened in the Songhua River water and the secondary effluent. The present study provided an insight into the complex oxidation process for the degradation of micropollutants containing aromatic amine by ferrate in water treatment.

A novel visible light-driven oxygen doped C3N4/Bi12O17Cl2/ferrate(VI) system for Bisphenol A degradation: Radical and nonradical pathways.

In this study, visible light-activated photocatalyst oxygen-doped C3N4@Bi12O17Cl2 (OCN@BOC) and Fe(VI) coupling system was proposed for the efficient degradation of bisphenol A (BPA). The comprehensive characterization of the OCN@BOC photocatalyst revealed its excellent photogenerated carrier separation rate in heterogeneous structures. The OCN@BOC/Fe(VI)/Vis system exhibited a remarkable BPA removal efficiency of over 84% within 5 min. Comparatively, only 37% and 59% of BPA were degraded by single OCN@BOC and Fe(VI) in 5 min, respectively. Reactive species scavenging experiments, phenyl sulfoxide transformation experiments, and electron paramagnetic resonance experiments confirmed the involvement of superoxide radicals (⋅O2-), singlet oxygen (1O2), as well as iron(V)/iron(IV) (Fe(V)/Fe(IV)) species in the degradation process of BPA. Furthermore, density functional theoretical calculations and identification of intermediates provided insights into the potential degradation mechanism of BPA during these reactions. Additionally, simulation evaluations using an ecological structure activity relationship model demonstrated that the toxicity of BPA to the ecological environment was mitigated during its degradation process. This study presented a novel strategy for removing BPA utilizing visible light photocatalysts, highlighting promising applications for practical water environment remediation with the OCN@BOC/Fe(VI)/Vis system.

Ferrate(VI) assists in reducing cytotoxicity and genotoxicity to mammalian cells and organic bromine formation in ozonated wastewater.

Ozonation of wastewater containing bromide (Br-) forms highly toxic organic bromine. The effectiveness of ozonation in mitigating wastewater toxicity is minimal. Simultaneous application of ozone (O3) (5 mg/L) and ferrate(VI) (Fe(VI)) (10 mg-Fe/L) reduced cytotoxicity and genotoxicity towards mammalian cells by 39.8% and 71.1% (pH 7.0), respectively, when the wastewater has low levels of Br-. This enhanced reduction in toxicity can be attributed to increased production of reactive iron species Fe(IV)/Fe(V) and reactive oxygen species (•OH) that possess higher oxidizing ability. When wastewater contains 2 mg/L Br-, ozonation increased cytotoxicity and genotoxicity by 168%-180% and 150%-155%, respectively, primarily due to the formation of organic bromine. However, O3/Fe(VI) significantly (p < 0.05) suppressed both total organic bromine (TOBr), BrO3-, as well as their associated toxicity. Electron donating capacity (EDC) measurement and precursor inference using Orbitrap ultra-high resolution mass spectrometry found that Fe(IV)/Fe(V) and •OH enhanced EDC removal from precursors present in wastewater, inhibiting electrophilic substitution and electrophilic addition reactions that lead to organic bromine formation. Additionally, HOBr quenched by self-decomposition-produced H2O2 from Fe(VI) also inhibits TOBr formation along with its associated toxicity. The adsorption of Fe(III) flocs resulting from Fe(VI) decomposition contributes only minimally to reducing toxicity. Compared to ozonation alone, integration of Fe(VI) with O3 offers improved safety for treating wastewater with varying concentrations of Br-.

The effect of temperature on the rate of oxygen evolution reaction during ferrate(VI) synthesis by anodic dissolution of iron in highly alkaline media.

This study investigates the effect of temperature on the rate of the oxygen evolution reaction (OER) during the electrochemical production of ferrate(VI) through anodic iron dissolution. We employed a membrane-divided electrochemical cell with a galvanostatically operated three-electrode setup. During the experiments, we recorded the anode potential at various temperatures and monitored temperature variations over time. Simultaneously, we measured the rates of ferrate(VI) formation and the oxygen evolution reaction. The latter, considered a parasitic reaction, competes with ferrate synthesis. By quantifying the extent to which the OER consumed the applied charge, we discovered that the OER rate decreases with temperature. Specifically, at 25 °C and 168 Am-2, the OER consumes more than double the charge of the produced ferrate, at higher temperatures the rate sensibly decays and with it the consumed charge by the OER. The specific energy required for ferrate(VI) production decreases as temperatures increase, aligning well with current efficiency and space-time yield values within the same temperature range.