Search Results (31)

To mitigate membrane fouling in the ultrafiltration process of surface water, this study focused on the source water from the Songhua River, systematically investigating the efficacy and mechanism of combined ferrate(VI) (Fe(VI)) and manganese(II) (Mn(II)) pretreatment in controlling ultrafiltration membrane fouling. Emphasis was placed on analyzing the impacts of pretreatment on membrane fouling performance, physicochemical properties of influent and effluent, membrane surface characteristics, and interfacial interactions. The results showed that the combined pretreatment with Fe(VI) and Mn(II) outperformed individual pretreatments and the untreated group significantly. When Fe(VI)/Mn(II) was 2/3, the normalized flux reached 0.66, a 35% increase compared to the untreated group; meanwhile, the pollutants retention was enhanced to 41.5%, with reversible and irreversible fouling resistances reduced by 75% and 77%, respectively. At this optimal ratio, the reaction products of Fe(VI) and Mn(II) coagulation acted as the core mechanism. It enhances pollutant particle repulsion, reduces particle size to form a loose structure, leading to a porous, hydrophilic membrane surface fouling layer with low roughness, thus minimizing membrane pore blockage. The combined pretreatment maintained a repulsive total interaction energy between pollutants and the membrane throughout the process, significantly reducing irreversible adsorption, which further verified the effectiveness of fouling mitigation. This study demonstrated that combined Fe(VI)/Mn(II) pretreatment at a molar ratio of 2:3 could efficiently control ultrafiltration membrane fouling by regulating pollutant characteristics and interfacial interactions, providing a theoretical basis and technical support for advanced treatment of surface water. Full article

Fenton oxidation can contribute to meeting effluent standards for COD in actual wastewater treatment plant effluents. However, Fenton oxidation is prone to produce iron sludge waste. The application of heterogeneous Fenton-like systems based on Fenton iron mud carbon in wastewater treatment plants is essential for Fenton iron mud reduction and recycling. In this study, a Fenton iron mud carbon catalyst/Ferrate salts/H₂O₂ (FSC/Fe(VI)/H₂O₂) system was developed to remove chemical oxygen demand (COD) from secondary effluents at the pilot scale. The results showed that the FSC/Fe(VI)/H₂O₂ system exhibited excellent COD removal performance with a removal rate of 57% under slightly neutral conditions in laboratory experiments. In addition, the effluent COD was stabilized below 40 mg·L⁻¹ for 65 days at the pilot scale. Fe(IV) and ¹O₂ were confirmed to be the main active species in the degradation process through electron paramagnetic resonance (EPR) and quenching experiments. C=O, O-C=O, N sites and Fe⁰ were responsible for the generation of Fe(IV) and ¹O₂ in the FSC/Fe(VI)/H₂O₂ system. Furthermore, the cost per ton of water treated by the pilot-scale FSC/Fe(VI)/H₂O₂ system was calculated to be only 0.6209 USD/t, further confirming the application potential of the FSC/Fe(VI)/H₂O₂ system. This study promotes the engineering application of heterogeneous Fenton-like systems for water treatment. Full article

Ferrate (Fe(VI)), an emerging green oxidant and disinfectant in water treatment, faces challenges due to its limited reaction efficiency stemming from a highly electron-deficient state. To address this, we designed NiFe-Layered Double Hydroxides (NiFe-LDHs) with different spin states to enhance electron transfer efficiency in Fe(VI)-mediated advanced oxidation processes (AOPs). We hypothesized that fine-tuning the spin state of NiFe-LDHs could optimize the balance between adsorption capabilities and electronic structure regulation. Our experiments revealed that intermediate-spin NiFeLDH-1, with a magnetic moment of 0.67 μB, exhibited the best catalytic performance, achieving 100% phenol removal. The NiFeLDH-x/Fe(VI) system demonstrated a significant synergistic enhancement in degradation efficiency. In addition, NiFeLDH-1 showed excellent performance in stability and continuous flow experiments. This study unveils a novel correlation between spin polarization and catalytic efficiency, offering insights into the optimization of electrocatalysts for Fe(VI)-mediated AOPs. The findings suggest that spin state modulation is a promising strategy to enhance the electrocatalytic activity and stability of non-noble metal catalysts. Full article

Interest in the combination of ferrates and advanced oxidation processes (AOPs) for wastewater treatment has increased, as revealed in this systematic review. In this study, the multiple functions of Fe(VI) in ferrate-based AOPs are summarized based on the Fe species. Various enhanced oxidation pathways are achieved through electron capture by Fe(VI), oxidation by Fe(V) and Fe(IV), or the catalytic effects of Fe(III) and Fe(II). The different contributions of high-valent Fe species and general reactive oxidation species are highlighted by analyzing the results of quenching, methyl phenyl sulfoxide probing, and electron paramagnetic resonance analysis. Methods that are used to adjust the Fe species, including changing the reaction pH, oxidant dosage, dosing pattern, and the addition of reducing or complexing additives, can influence the enhancement efficiency of micropollutant treatment from the perspective of determining the transformation from Fe(VI) to Fe(V) and Fe(IV) with higher reactivity or Fe(III) and Fe(II) circulation. Future studies should focus on the in situ production of high-valent Fe and oxidation pathway-based adjustments in Fe(VI)-AOP techniques. Full article

Potassium ferrate(VI) (K₂FeO₄) as a particularly strong oxidant represents an effective and environmentally friendly waste water treatment material. When produced by anodic oxidation in highly alkaline aqueous solution, the K₂FeO₄ product is separated and sealed in inert plastic bags with the retention of some liquid phase with high pH. This method proved to be excellent for long-term storage at moderately low temperature (5 °C) for industrial applications. It is still imperative to check the ferrate(VI) content of the product whenever it is to be used. Fe-57 Mössbauer spectroscopy is an excellent tool for checking the ratio of ferrate(VI) to the degradation product iron(III) in a sample. For this purpose, normally the spectral areas of the corresponding subspectra are considered; however, this approximation neglects the possible differences in the corresponding Mössbauer–Lamb factors. In this work, we have successfully determined the Mössbauer–Lamb factors for the ferrate(VI) and for the most common iron(III) degradation products observed. We have found superparamagnetic behavior and low-temperature phase transformation for another iron(III) degradation product that made the determination of the Mössbauer–Lamb factors impossible in that case. The identities of a total of three different iron(III) degradation products have been confirmed. Full article

An Fe(III)-carbonato six-coordinate picket fence porphyrin complex with the formula [K(2,2,2-crypt)][Fe^III(TpivPP)(CO₃)]·C₆H₅Cl·3H₂O (I) has been synthesized and characterized by UV-Vis and FT-IR spectra. The structure of (carbonato)(α,α,α,α-tetrakis(o-pivalamidophenyl)porphinato)ferrate(III) was also established by XRD. The iron atom is hexa-coordinated by the four nitrogen atoms of the pyrrol rings and the two oxygen atoms of the CO₃²⁻ group. Complex I, characterized as a ferric high-spin complex (S = 5/2), presented higher Fe-Np (2.105(6) Å) and Fe-P_C (0.654(2) Å) distances. Both X-ray molecular structure and Hirshfeld surface analysis results show that the crystal packing of I is made by C-H⋯O and C-H⋯Cg weak intermolecular hydrogen interactions involving neighboring [Fe^III(TpivPP)(CO₃)]⁻ ion complexes. Computational studies were carried out at DFT/B3LYP-D3/LanL2DZ to investigate the HOMO and LUMO molecular frontier orbitals and the reactivity within the studied compound. The stability of compound I was investigated by analyzing both intra- and inter-molecular interactions using the 2D and 3DHirshfeld surface (HS) analyses. Additionally, the frontier molecular orbital (FMO) calculations and the molecular electronic potential (MEP) analyses were conducted to determine the electron localizations, electrophilic, and nucleophilic regions, as well as charge transfer (ECT) within the studied system. Full article

Algal blooms are caused by excessive levels of nitrogen, phosphorus, and other plant nutrients in water. Algae and algal organic matter (AOM) pose a great threat to the quality of drinking water. This manuscript offers a systematic review of algal removal by ferrate (Fe(VI)) oxidation, including the conditions for the removal of different algae by Fe(VI) and the factors affecting the removal efficiency. On this basis, the oxidation and coagulation mechanisms of algae removal by Fe(VI) are discussed. Then, the review introduces the process combining Fe(VI) pre-oxidation with aluminum sulfate action. The addition of aluminum sulfate can further enhance the coagulation effect and reduce the formation of disinfection byproducts (DBPs) in the subsequent chlorination process by effectively removing AOM, which is recognized as a precursor of DBPs. In addition, recent studies on the combined application of Fe(VI) and Fe(II) are also reviewed. In a reasonable dose range, the synergistic effect of Fe(VI) and Fe(II) can significantly improve the removal of algae and algal toxins. Finally, this review provides a comprehensive evaluation of the applicability of Fe(VI) in removing algal material, offers guidance for the harmless treatment of algae with Fe(VI), and identifies future research questions. Full article

Butylated hydroxyanisole (BHA), a synthetic phenolic antioxidant (SPA), is now widely present in natural waters. To improve the degradation efficiency of BHA and reduce product toxicity, a combination of peroxymonosulfate (PMS) and Ferrate(VI) (Fe(VI)) was used in this study. We systematically investigated the reaction kinetics, mechanism and product toxicity in the degradation of BHA through the combined use of PMS and Fe(VI). The results showed that PMS and Fe(VI) have synergistic effects on the degradation of BHA. The effects of operational factors, including PMS dosage, pH and coexisting ions (Cl⁻, SO₄²⁻, HCO₃⁻, K⁺, NH₄⁺ and Mg²⁺), and different water matrices were investigated through a series of kinetic experiments. When T = 25 °C, the initial pH was 8.0, the initial BHA concentration was 100 μM, the initial concentration ratio of [PMS]₀:[Fe(VI)]₀:[BHA]₀ was 100:1:1 and the degradation rate could reach 92.4% within 30 min. Through liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) identification, it was determined that the oxidation pathway of BHA caused by PMS/Fe(VI) mainly includes hydroxylation, ring-opening and coupling reactions. Density functional theory (DFT) calculations indicated that ^•OH was most likely to attack BHA and generate hydroxylated products. The comprehensive comparison of product toxicity results showed that the PMS/Fe(VI) system can effectively reduce the environmental risk of a reaction. This study contributes to the development of PMS/Fe(VI) for water treatment applications. Full article

Chemical warfare agents (CWAs) are one of the most toxic compounds. Degradation of CWAs using decontamination agents is one of the few ways to protect human health against the harmful effects of CWAs. A ferrate (VI)-based potential chemical warfare agent decontaminant was studied for the degradation of persistent nitrogen mustard (tris(2-chloroethyl)amine, HN3). By optimizing the reaction conditions, the complete degradation of HN3 was achieved in 4 min. The degradation products contained mostly reduced Fe species, which confirmed the environmental friendliness of the proposed decontamination solution. Full article

Doxycycline (DOX), a typical antibiotic, is harmful to aquatic ecosystems and human health. This study presents DOX removal by potassium ferrate (Fe(VI)) and montmorillonite and investigates the effect of Fe(VI) dosage, reaction time, initial pH value, montmorillonite dosage, adsorption pH, time and temperature on DOX removal. The results show that DOX removal increases when increasing the Fe(VI) dosage, with the optimal condition for DOX removal (~97%) by Fe(VI) observed under a molar ratio ([Fe(VI)]:[DOX]) of 30:1 at pH 7. The reaction of DOX with Fe(VI) obeyed second-order kinetics with a rate constant of 10.7 ± 0.45 M⁻¹ s⁻¹ at pH 7. The limited promotion (~4%) of DOX adsorption by montmorillonite was observed when the temperature increased and the pH decreased. Moreover, the synergetic effect of Fe(VI) and montmorillonite on DOX removal was obtained when comparing the various types of dosing sequences (Fe(VI) oxidation first and then adsorption; adsorption first and then Fe(VI) oxidation; simultaneous oxidation and adsorption). The best synergistic effect of DOX removal (97%) was observed under the simultaneous addition of Fe(VI) and montmorillonite, maintaining the Fe(VI) dosage (from 30:1 to 5:1). Five intermediates were detected during DOX degradation, and a plausible DOX degradation pathway was proposed. Full article

Iron species can act as electron donors, electron acceptors or serve as a sorbent to co-precipitate contaminants. These properties, along with its relatively low cost as a material, make iron an ideal compound for environmental applications in the removal of pollutants from water and wastewater. This study assesses the use of metallic iron as a reductant for the removal of toxic Cr(VI) from aqueous solutions, as well as the use of hexavalent iron (ferrates) for the removal of organic compounds, turbidity and biological contaminants from water and wastewater. Laboratory-scale experiments show that the Cr(VI) removal efficiency of metallic iron filling materials, such as scrap iron fillings, via reduction to Cr(III) and the subsequent precipitation/filtration of aggregates can reach values over 99.0%. Moreover, the efficiency of ferrates, in situ synthesized via a low-cost Fe⁰/Fe⁰ electrochemical cell, in the removal of organic compounds, turbidity and biological contaminants from high-strength industrial wastewater, biologically treated wastewater and natural water can also reach values over 99.0%. The results showed that iron species can be applied in low-cost and environmentally friendly technologies for natural water remediation and wastewater treatment. Furthermore, the study showed that the challenge of an iron material’s surface passivation, as well as of ferrates’ procurement cost and stability, can be resolved via the application of ultrasounds and via in situ ferrate electrosynthesis. Full article

The aim of this study is to evaluate the effects of ferrate (VI)-based treatment on surface water collected from the Rímac River as an irrigation water treatment model for bean (Phaseolus vulgaris), lettuce (Lactuca sativa), and radish (Raphanus sativus) plant species irrigated with treated water in the experimental field. The experimental field was divided into eight 625 m² plots (50 m × 12.5 m) with sandy loam soil (sand 51%, silt 30%, clay 19%). The treatment system operated uninterrupted for three and a half months without deterioration in production, demonstrating that it can function continuously to improve water quality even when the effects on the parameters evaluated here did not reveal significant differences, presumably due to the prevailing effect from metal concentrations already found in the soil. This study also seeks to validate the effect of treatment on the concentration of plant tissue bacteria. Full article

Ferrate(VI) is a green and efficient water treatment agent for drinking and wastewater. It is widely used in water treatment because it has multi-functional uses such as oxidation, algae removal, disinfection, and adsorption flocculation. It does not cause secondary pollution to the environment. This paper compares ferrate(VI) with other water treatment agents and discusses three methods of preparing ferrate(VI). The removal, adsorption, and control of organic matter, algae, disinfection by-products, and heavy metal ions in water when ferrate(VI) was used as an oxidant, disinfectant, and coagulant were summarized. Ferrate(VI) has some advantages in removing toxic, harmful, and difficult-to-degrade substances from water. Due to the disadvantages of ferrate(VI) such as oxidation selectivity and instability, it is necessary to develop the hyphenated techniques of ferrate(VI). In this review, three hyphenated techniques of ferrate(VI) are summarized: ferrate(VI)–photocatalytic synergistic coupling, ferrate(VI)–PAA synergistic coupling, and ferrate(VI)–PMS synergistic coupling. Full article

Dissolved organic phosphorus (DOP), which is recalcitrant in municipal wastewater treatment, accounts for 26–81% of dissolved total phosphorus in the effluent. More importantly, the majority of DOP could be bioavailable, potentially threatening the aquatic environment through eutrophication. This study aimed to develop a ferrate (VI)-based advanced treatment to effectively destruct and remove DOP from secondary effluent and use deoxyribonucleic acid (DNA) and adenosine-5’-triphosphate (ATP) as DOP model compounds to explore the relevant mechanisms. The results showed that ferrate (VI) treatment could efficiently destruct and remove 75% of the DOP in secondary effluent from an activated sludge-adopted municipal wastewater treatment plant, under normal operating conditions. Moreover, the coexistence of nitrate, ammonia, and alkalinity barely affected the effectiveness, while the presence of phosphate significantly inhibited DOP removal. The mechanistic study revealed that ferrate (VI)-induced particle adsorption was the dominant way to achieve DOP reduction, rather than oxidating DOP to phosphate and forming precipitation afterward. Meanwhile, DOP molecules could be effectively decomposed into smaller ones by ferrate (VI) oxidation. This study clearly demonstrated that ferrate (VI) treatment could achieve a promising DOP removal from secondary effluent for mitigating the risk of eutrophication in receiving water bodies. Full article

Occurrence of micropollutants in water and their potential impact on the environment and human health are arising concerns. The micropollutants are not removed efficiently by current wastewater treatment and a small amount of them get released into receiving waters accompanying the discharging of the treated wastewater effluents. Therefore, it is useful to investigate an advanced or alternative technology to remove traces of micropollutants in Lake Constance water during drinking water treatment. Among various oxidation processes, ferrate(VI) has received extensive attentions due to its superior dual properties of oxidation and coagulation. The work in this communication is the first trial using ferrate(VI) in comparison with FeCl₃/ozonation to treat lake water and to remove micropollutants in the region. The results of pilot-scale trials showed that 10% of metformin, benzotriazole and acesulfam can be removed by ferrate(VI) at a dose of 0.1 mg L⁻¹ from raw water, but FeCl₃ with or without pre-ozonation cannot achieve the same performance. The degradability of three additional micropollutants by ferrate(VI) oxidation followed the sequences of bisphenol-S (BS) > azithromycin (AZM) > imidacloprid (IMP) was evaluated, and 100% concentration reduction of BS was achieved. The work suggests that ferrate(VI) is a potential alternative to the existing treatment processes for drinking water treatment. Full article