Effect Of Ferrate Research Articles

Degradation of the endocrine-disrupting 4-nonylphenol by ferrate(VI): biodegradability and toxicity evaluation.

4-Nonylphenol (4-NP) is an endocrine-disrupting and persistent chemical and is partially degraded in conventional wastewater treatment processes. Ferrate(VI) can be used as an environment-friendly oxidizing agent to mediate 4-NP degradation. Thus, this paper evaluates the biodegradability of 4-NP and its degradation products after the addition of ferrate(VI). The biodegradability was examined using NP labeled with 14C as a tracer and activated sludge microorganisms as an inoculum. The addition of ferrate(VI) to the 4-NP solution spiked with the tracer resulted in no remarkable decrease in the concentration of 14C, indicating incomplete mineralization of 4-NP and formation of degradation products. The degradation products from 4-NP with Fe(VI) were estimated based on mass spectra, which detected a unique peak at m/z 223 at low intensity. Four hydrogen atoms might have been added to 4-NP by degradation with Fe(VI). In addition, the effect of ferrate(VI) concentration on the estrogenic activity of 4-NP in an aqueous solution was investigated using a yeast bioassay. The results show that estrogenic activity was significantly decreased at a mass ratio of Fe(VI) to 4-NP greater than or equal to 2.5.

Synergistic mechanism of combined ferrate and ultrafiltration process for shale gas wastewater treatment

The operational issues of low-pressure ultrafiltration (UF) membrane are associated with its long-term membrane fouling caused by organic and inorganic matters, especially in treating shale gas wastewater (SGW) with complex water compositions. Herein, the effect of ferrate (Fe(VI)) pretreatment on UF membrane fouling and water quality in treating SGW was systematically investigated. Fe(VI) pretreatment significantly mitigated membrane fouling and slightly improved the effluent quality. The hydraulically irreversible fouling index and the total fouling index decreased by 69%–87% and 58%–84%, respectively. The mechanism of membrane fouling mitigation was comprehensively analyzed by the classical pore blocking model, correlation analysis between membrane fouling index and water quality, and the extended Derjaguin-Landau-Verwey-Overbeek theory. The synergistic mechanisms of membrane fouling mitigation were as follows: (i) Macromolecular organic matters (high molecular weight humics and biopolymers) which would block the membrane pores were oxidized into low fractions organics and removed by Fe(VI); (ii) Fe(VI) pretreatment improved interaction free energy of cohesion of foulants-foulants making foulants more hydrophilic and stable, and increased interaction free energy of adhesion of membrane-foulants making it more difficult for foulants to deposit on the membrane surface. Fe(VI) pretreatment had huge potential in alleviating membrane fouling in treating SGW and other complex wastewater.

Oxidative treatment of bisphenol A in municipal wastewater reverse osmosis concentrate using Ferrate(VI)

Reverse osmosis concentrate (ROC) resulting from the municipal wastewater recycling processes poses significant environmental and health risks as it contains significant concentrations of harmful compounds, including phenolic chemicals including bisphenol A (BPA). In this study, the effect of ferrate(VI) (or Fe(VI)) oxidation on the degradation of BPA (50 µg L−1) in a typical ROC matrix was investigated. The influence of process variables including the [Fe(VI)]/[BPA] ratios (7–50), initial pH (5.0–8.0) and reaction temperature (15–25 °C) was studied. Fe(VI) was found to be highly effective in degrading BPA in the complex ROC matrix with various operating conditions. At 25 °C, over 90% degradation of BPA was achieved at the [Fe(VI)]/[BPA] ratio of 50, and an initial pH of the ROC at 8.0 after 90 min of reaction. Under such conditions, the reduction in dissolved organic carbon (DOC) was found to be 34% accompanied by a 95% reduction in UV254 absorbance (initial value 0.750 cm−1) with 96.4% SUVA reduction. Additionally, the residual concentration of Fe(III) at pH 8.0 was the lowest compared to other pH conditions at a fixed [Fe(VI)]/[BPA] ratio of 50. Fluorescence regional integration (FRI) analyses revealed that Fe(VI) preferentially react with fulvic acid-like and humic acid-like compounds, and aromatic protein II in the ROC. This indicated Fe(VI) effectively breaking down electron-rich moieties groups including phenols and other organics in ROC. The apparent second-order rate constant (kapp) for BPA degradation was determined to be 2.27 × 102 M−1 s−1 at pH 8.0 at a [Fe(VI)]/[BPA] ratio of 50, and the value of reaction rate constant increased proportionally with increasing molar ratio at the range studied. The effectiveness of Fe(VI) in the degradation of BPA in the ROC demonstrates the potential of using Fe(VI) as an efficient oxidant to remediate the micropollutants present in water and wastewater.

Effect of ferrate and monochloramine disinfection on the physiological and transcriptomic response of Escherichia coli at late stationary phase

Biological mechanisms of disinfection not only vary by disinfectant but also remain not well understood. We investigated the physiological and transcriptomic response of Escherichia coli at late stationary phase to ferrate and monochloramine in amended lake water. Although ferrate and monochloramine treatments similarly reduced culturable cell concentrations by 3-log10, 64% and 11% of treated cells were viable following monochloramine and ferrate treatment, respectively. This observed induction of viable but non-culturable (VBNC) state following monochloramine treatment but not ferrate is attributed to slower monochloramine disinfection kinetics (by 2.8 times) compared to ferrate. Transcriptomic analysis of E. coli at 15 min of exposure revealed that 3 times as many genes related to translation and transcription were downregulated by monochloramine compared to ferrate, suggesting that monochloramine treatment may be inducing VBNC through reduced protein synthesis and metabolism. Downregulation of universal stress response genes (rpoS, uspA) was attributed to growth-related physiological stressors during late stationary phase which may have contributed to the elevated expression levels of general stress responses pre-disinfection and, subsequently, their significant downregulation post-disinfection. Both disinfectants upregulated oxidative stress response genes (trxC, grxA, soxS), although levels of upregulation were time sensitive. This work shows that bacterial inactivation responses to disinfectants is mediated by complex molecular and growth-related responses.

Flotation separation of molybdenite from chalcopyrite using ferrate(VI) as selective depressant in the absence of a collector

The effect of ferrate on the flotation of chalcopyrite and molybdenite in the absence of a collector was studied in this work. Flotation tests on single minerals revealed that chalcopyrite was strongly depressed by the ferrate for pH ranging from 4 to 9, whereas molybdenite was only slightly affected. The flotation tests on mineral mixtures and real ore confirmed that ferrate could selectively depress chalcopyrite flotation without significantly affecting molybdenite floatation. Under the optimum conditions, a value of >60% was obtained for the difference between the recovery of chalcopyrite and molybdenite. X-ray photoelectron spectroscopy results revealed that the oxide and hydroxide content and iron content of the chalcopyrite surface increased from 55.42% to 74.80% and 2.56% to 5.15%, respectively. This confirmed that the ferrate-treated chalcopyrite surface was more hydrophilic than the untreated surface. Therefore, ferrate can be used as a selective depressant of chalcopyrite in copper-molybdenum separation within a wide pH range.

Micropollutants in wastewater and their degradation by ferrates (VI)

Abstract In recent years, the occurrence of micropollutants (MPs) in sewage-, surface-, ground- and drinking water, and their removal processes are widely discussed. The content of various chemical organic/inorganic pollutants (pharmaceuticals, drugs, pesticides, hormones, heavy metals etc.) has increased over the years. Most of these compounds are not eliminated or biotransformed in traditional wastewater treatment plants. Several advanced oxidation processes (AOPs) for the removal of resistant micropollutants from water sources have been studied. Ferrate (VI) has aroused interest as an alternative oxidizing agent in drinking water preoxidation treatment. Electrochemically prepared potassium ferrate was used to remove the studied organic micropollutants. The effect of ferrate on two widely occurring organic micropollutants in water sources, carbamazepine and caffeine, was investigated. High performance liquid chromatography (HPLC) was used for sample analysis.

Effect of ferrate on green algae removal.

Green algae Cladophora aegagropila, present in cooling water of thermal power plants, causes many problems and complications, especially during summer. However, algae and its metabolites are rarely eliminated by common removal methods. In this work, the elimination efficiency of electrochemically prepared potassium ferrate(VI) on algae from cooling water was investigated. The influence of experimental parameters, such as Fe(VI) dosage, application time, pH of the system, temperature and hydrodynamics of the solution on removal efficiency, was optimized. This study demonstrates that algae C. aegagropila can be effectively removed from cooling water by ferrate. Application of ferrate(VI) at the optimized dosage and under the suitable conditions (temperature, pH) leads to 100% removal of green algae Cladophora from the system. Environmentally friendly reduction products (Fe(III)) and coagulation properties favour the application of ferrate for the treatment of water contaminated with studied microorganisms compared to other methods such as chlorination and use of permanganate, where harmful products are produced.

Removal of phosphorus and coliforms from secondary effluent using ferrate(VI)

The potassium ferrate(VI) was applied to treat secondary wastewater and its performance as both a disinfectant and a coagulant was investigated. In order to compare oxidation potential of the ferrate(VI) with that of chlorine, the different condition of doses and contact times were applied to the experiment for the same coliform. The disinfection rate of ferrate(IV) was faster than that of chlorine at the same concentration. The effect of ferrate(VI) supplementation on coagulation of phosphorus was examined and compared with other common coagulants. Ferrate(VI) reduced more than 80% of total phosphorous in the range of doses between 5. and 25 mg-Fe/L. The removal efficiencies of the ferrate(VI) appeared to be similar to those of alum but higher than other iron coagulants. The removal efficiencies of other contaminants in secondary effluent were not notable.

Investigation of electrochemical synthesis of ferrate, Part I: Electrochemical behavior of iron and its several alloys in concentrated alkaline solutions

In recent years, considerable attention has been paid to various applications of Fe(VI) due to its unique properties such as oxidizing power, selective reactivity, stability of the salt, and non-toxic decomposition by-products of ferric ion. In environmental remediation processes, Fe(VI) has been proposed as green oxidant, coagulant, disinfectant, and antifoulant. Therefore, it is considered as a promising multi-purpose water treatment chemical. Fe(VI) has also potential applications in electrochemical energy source, as 'green cathode'. The effectiveness of ferrate as a powerful oxidant in the entire pH range, and its use in environmental applications for the removal of wide range of contaminants has been well documented by several researchers. There is scientific evidence that ferrate can effectively remove arsenic, algae, viruses, pharmaceutical waste, and other toxic heavy metals. Although Fe(VI) was first discovered in early eighteen century, detailed studies on physical and chemical properties of Fe(VI) had to wait until efficient synthetic and analytical methods of Fe(VI) were developed by Schreyer et al. in the 1950s. Actually, there have been developed three ways for the preparation of Fe(VI) compounds : the wet oxidation of Fe(II) and Fe(III) compounds, the dry oxidation of the same, and the electrochemistry method, mainly based on the trans passive oxidation of iron. High purity ferrates Fe(VI) can be generated when electrode of the pure iron metal or its alloys are anodized in concentrated alkaline solution. It is known that the efficiency of electrochemical process of Fe(VI) production depends on many factors such as current density, composition of anode material, types of electrolyte etc. In this paper, the electrochemical synthesis of ferrate(VI) solution by the anodic dissolution of iron and its alloys in concentrated water solution of NaOH and KOH is investigated. The process of transpassive dissolution of iron to ferrate(VI) was studied by cyclic voltammetry, galvanostatic and potentiostatic pulse method. Cyclic voltammetry gave useful data on potential regions where ferrate(VI) formation is to be expected in the course of transpassive anodic oxidation of iron and some of its alloys, and its stability in the electrolytes of different composition. In addition, step-wise oxidation of iron in anodic oxidation is confirmed. Galvanostatic pulse experiments confirmed the character of successive anodic oxidation of iron, as the three-step process of ferrate(VI) formation is clearly observed. In the cathodic pulse complex reduction of ferrate (VI), firstly to Fe(III) species and then to mixed Fe(II) and Fe(III) compounds and finally to elementary iron is confirmed. The significant difference between the mechanisms of anodic oxidation of pure iron and low carbon steel at the one side and electrical ferrous-silicon steel at the other is observed. The influence of material chemical composition on the electrochemical behavior of electrode in course of anodic polarization in strong alkaline solutions is discussed in terms of composition of passivating layer formed on the electrode. On the base of the experimental data, efficient synthesis of ferrate(VI) can be expected in the region of anodic potentials between + 0,55 and + 0,75 V against Hg|HgO reference electrode in the same solution, depending on the anode materials composition, in the alkaline electrolytes concentration between 10 and 15 M.

Effect of ferrate, a site-specific phosphate analog, on human deoxyhemoglobin

Ferrate ion, a phosphate analog and a potent oxidizing agent, is known to inactivate a number of enzymes which interact with phosphoryl compounds. In contrast, enzymes which do not interact with phosphoryl compounds are not affected by comparable concentrations of ferrate. To further explore the specificity of ferrate as a reagent which is specific for phosphoryl binding sites, a study of its effect on human hemoglobin A was undertaken. In the deoxy form, this protein is known to interact with 2,3-bisphosphoglycerate, its natural allosteric inhibitor of cooperative binding of oxygen, while as oxyhemoglobin it does not interact with the inhibitor. Treatment with ferrate ion caused the loss of approximately three amino acid residues per β chain of human deoxyhemoglobin, His-2, His-143, and Tyr-145, and one residue, presumably Tyr-42, per α chain. Oxyhemoglobin was not affected by the reagent. 2,3-Bisphosphoglycerate was found to protect deoxyhemoglobin from the action of ferrate. His-2 and His-143 are among the residues reported to be implicated in the binding of 2,3-bisphosphoglycerate by deoxyhemoglobin [A. Arnone (1972) Nature (London) 237, 146–148] .