Search Results (37)

Ferrate(VI) has increasingly been proposed as an environmentally friendly oxidant due to its high reactivity and the relatively low toxicity of its by-products. However, its performance in degrading emerging pollutants (EPs) has not been systematically compared with conventional systems. This study presents a novel comparative assessment of three oxidation systems for the degradation of acetaminophen (APAP): (i) Fe⁰-activated hydrogen peroxide (HP), (ii) Fe⁰-activated persulfate (PS), and (iii) a commercial ferrate(VI)-based product, Envifer^® (Fe(VI)). Optimal conditions were determined based on degradation kinetics, pH dependence, and oxidant stability. Oxidant systems were then evaluated in realistic matrices, including tap water and synthetic wastewater. When UP water was used, the HP/Fe⁰ system achieved the highest APAP mineralization (i.e., 66%) with 1 mM of oxidant dosage, and PS/Fe⁰ was shown to be effective without pH adjustment. Nevertheless, these heterogeneous systems presented serious limitations when applied in more complex matrices. Fe(VI) instead achieved a rapid APAP degradation even in the presence of carbonates and natural organic matter without pH adjustment. This represents a key advantage over HP- and PS-based systems, enabling simpler implementation and lower chemical demand. Furthermore, Fe(VI) resulted in lower dissolved iron concentrations, potentially enabling less intensive post-treatment requirements. Overall, the results identify Fe(VI)-based AOPs as a potentially green alternative to conventional systems for wastewater treatment. Full article

Acid Black 1 (AB1), a recalcitrant disazo dye from the textile industry, poses a severe threat to aquatic ecosystems owing to its resistance to biological treatment. Although ferrate(VI) (${\mathrm{K}}_2\mathrm{Fe}{\mathrm{O}}_4)$ and plasma-based advanced oxidation processes have shown promise for dye remediation, the effect of treatment sequence on synergistic mineralization remains largely unaddressed. Nano-ferrate(VI) (nano-Fe(VI), ${\mathrm{K}}_2\mathrm{Fe}{\mathrm{O}}_4$) synthesized via the Solution Plasma Process (SPP) was integrated with Gliding Arc Plasma (GAP) in a sequential hybrid system, with nanoscale morphology and ${\mathrm{K}}_2\mathrm{F}\mathrm{e}{\mathrm{O}}_4$ composition confirmed by FE-SEM and EDS. pH, molar ratio, and temperature were systematically optimized for the standalone nano-Fe(VI) process, and synergistic performance was evaluated via Synergy Effect Factor (SEF) analysis. Optimization identified pH 7.0, [AB1]:[Fe(VI)] = 1:0.9, and 45 °C as optimal, achieving 90.24% decolorization within 12 min. The sequential nano-Fe(VI)–GAP configuration achieved the highest mineralization efficiency of 58.7%, outperforming standalone nano-Fe(VI) (36.0%), standalone GAP (16.0%), and simultaneous application (37.8%), with SEF values of 1.3 and 1.2 for mineralization and decolorization. This is the first study to quantify treatment sequence effects in a nano-Fe(VI)–GAP system via SEF analysis. The proposed system eliminates intermediate pH adjustment while achieving superior mineralization, offering a practical AOP framework for refractory textile wastewater treatment. Full article

The relative position of the oxime group within pharmaceutically relevant pyridinium oximes is a pivotal factor that governs their intrinsic physicochemical properties and their biological reactivity. However, studies providing in-depth, molecular-level insight into these structure–reactivity relationships are still limited. In this work, we present an integrated experimental and computational study of N-methylpyridinium-2-aldoxime chloride (PAM2-Cl), N-methylpyridinium-3-aldoxime iodide (PAM3-I), and N-methylpyridinium-4-aldoxime iodide (PAM4-I), aimed at elucidating discrete differences in their ionization behavior, electronic structure, σ-donor properties, and nucleophilicity. The crystal structure of PAM3-I was determined by X-ray diffraction. Comparative structural and spectroscopic (UV–Vis, NMR, IR) analyses elucidated the structural and electronic effects arising from the position of the oxime group. Kinetic studies of substitution reactions with aquapentacyanoferrate(II) in aqueous solution enabled the determination of pentacyano(PAM)ferrate(II) formation and dissociation rate constants, coordination modes, pK_a values of the coordinated ligands, complex stability constants, and σ-donating capabilities. The DFT-based analysis of atomic charge distribution transcended experimental limitations, offering a new perspective on electronic structure-related properties. This study presents the first side-by-side, internally consistent structure–reactivity map across PAM2, PAM3, and PAM4 isomers that triangulates crystallography, UV–Vis-derived pK_a values, substitution kinetics, and DFT descriptors in a single framework. Full article

Acid violet 19 (AV19) dye is used in many fields, including photographic film, inks, leather, and textiles. Potassium ferrate (VI) (Fe(VI)) represents a novel oxidant, notable for its strong oxidative capabilities, stability, and environmental sustainability. This research investigates the decolorization and mineralization of AV19 through the application of Fe(VI), with a particular emphasis on essential parameters, including pH, molar ratios, and temperature variations. The study ascertained that the optimal conditions for AV19 oxidation are a pH of 7.0, a molar ratio of AV19: Fe(VI) of 1:5, and a temperature of 45 °C with a reaction time of 12 min. The decolorization efficiency achieved was approximately 98%, and the mineralization was 31%. The degradation process yielded intermediates, such as sulfonic acid derivatives, benzoic acid, benzene, and cyclohexane compounds, which were further oxidized into acetic acid, carbon dioxide, and water. Comprehensive computational toxicity evaluations confirmed that both the intermediates and the final products are non-toxic. Full article

Ferrate as an environmentally friendly oxidant has been widely used in the environmental remediation and versatile functionalization of carbon-based materials. In this study, we investigated its ability to induce surface wettability of polymers and its emerging applications in separating mixed plastics through flotation for recycling. It was found that ferrate (VI) formed oxygen-containing groups on the surface of polycarbonates (PCs) by selectively oxidizing the sp³-hybridized carbon atoms into hydroxyl and carboxyl moieties, in addition to introducing nanoscale iron oxides. This facilitated the selective hydrophilization of PC with a water contact angle of 60.7° but did not clearly affect the surface wettability of polyvinyl chloride (PVC). This difference in surface wettability highlighted the distinct floatability properties of PC and PVC, which can be utilized to separate mixtures of these plastics with the aid of flotation. A central composite design (CCD) utilizing response surface methodology (RSM) was applied to model ferrate oxidation and to optimize flotation. Under the optimized conditions, mixtures of PC and PVC were efficiently separated with recovery and purity values of more than 99.8 ± 0.3%. Our findings provide a rational understanding of polymer wettability tailoring and expand its emerging applications in waste plastic recycling to address environmental problems. Full article

In this study, three benign oxidants, potassium ferrate (Fe(VI)), sodium persulfate (PS), and sodium percarbonate (SPC), were combined with nonthermal plasma (NTP) to enhance the degradation of Malachite Green (MG) and Metanil Yellow (MY). Experimental factors, including dye concentration, oxidant dose, and treatment time, were optimized using Response Surface Methodology (RSM). The hybrid systems achieved markedly improved decolorization rates, with maximum efficiencies exceeding 99% within 30 min, compared to 96% for NTP alone. Kinetic analysis confirmed significantly higher rate constants for NTP-assisted oxidants, particularly NTP + Fe (VI) (k_obs = 0.127 min⁻¹), followed by NTP + PS (0.114 min⁻¹) and NTP + SPC (0.098 min⁻¹). Enhanced mineralization, together with stable pH and controlled conductivity variations, further substantiated the efficient breakdown of the dye molecules. Phytotoxicity assays demonstrated that untreated dyes severely inhibited germination. In contrast, effluents treated with NTP + PS and NTP + Fe (VI) restored germination and root growth to levels comparable to the deionized water (DIW) control, indicating substantial toxicity reduction. These results confirm that NTP-oxidants significantly improve oxidation performance, accelerate reaction kinetics, and yield environmentally safe effluents suitable for practical wastewater remediation. Full article

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