Fenton-like System Research Articles

Enhancement of iron cycling in Fenton-like catalysis by MoO2-C: Carbon-mediated efficient electron transport

In this study, the charge transfer capability of MoO2 materials was significantly improved by introducing carbon materials in situ. The resulting MoO2-C material could accelerate the Fe(III)/Fe(II) redox cycle and promote the continuous generation of reactive oxygen species in Fenton-like system. The results suggested that MoO2-C exhibited significant co-catalytic activity against a variety of pollutants. Meanwhile, the mechanisms behind the Fe(III)/Fe(II) cycle and reactive oxygen species generation were clarified. Analysis indicated that the incorporation of carbon material provided a reduction active site for the reduction of Fe(III) to Fe(II) on the surface of molybdenum oxide, and also reduced the thermodynamic energy barrier associated with Fe(III) reduction. Furthermore, quenching experiments and electron paramagnetic resonance (EPR) technology demonstrated that hydroxyl radicals (∙OH) and singlet oxygen (1O2) rapidly degrade the target pollutants. Fe(II) was verified as the primary component responsible for peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation. Additionally, the main generation pathway for 1O2 differed between the MoO2-C/Fe(III)/PDS and MoO2-C/Fe(III)/PMS systems. This study provides a new strategy to improve the iron reduction properties of metal oxide materials.

Iron/nitrogen/sulfur co-doped cyanobacteria derived carbon composites for enhanced hydroxychloroquine degradation via primary nonradical pathway in peroxymonosulfate-based fenton-like system

Iron/nitrogen/sulfur co-doped cyanobacteria derived carbon composites for enhanced hydroxychloroquine degradation via primary nonradical pathway in peroxymonosulfate-based fenton-like system

Structure tunning of MoS2@Fe3O4 by modulating electron density for enhanced Fenton-like PMS activation: Accelerated Fe (III)/Fe (II) cycle for efficient micropollutants removal

1T-MoS2 is a promising material for regulating the electronic structure of Fe-based catalyst to enhance PMS activation, due to the higher chemical reactivity of the basal plane with excellent intrinsic electronic properties. Herein, an excellent MoS2@Fe3O4 by using 1T- MoS2 as support to tune electronic structure, labeling as 1T-MoS2@Fe3O4, was successfully synthesized for faster and enhanced micropollutants degradation via Fenton-like peroxomonosulfate (PMS) activation. The composite showed remarkable catalytic performance, as evidenced by a removal rate of 1.12 × 10−1 min−1 for caffeine, which was 4.50 times higher than that of 2H-MoS2@Fe3O4, attributed to the robust capacity for Fe (II) regeneration. The efficiency of the 1T-MoS2@Fe3O4/PMS system was affected by pH, PMS and catalyst dosages, as well as water chemistry. Additionally, the potential mechanism for PMS activation was explored, showing that O2• were the dominant reactive oxygen species (ROS) generated in the system due to the electron-rich O sites on the composite, and electron transfer processes play an important role during PMS activation. The Mo (IV) active sites facilitated accelerated Fe (III)/Fe (II) cycle, which promoted the rapid PMS activation. Excellent degradation of micropollutants (MPs) mixture in real secondary effluent was achieved by 1T-MoS2@Fe3O4/PMS system. The possible degradation pathways of caffeine (CAF), ibuprofen (IBP), and carbamazepine (CBZ) were also investigated. This study offers a new perspective on MoS2 as a co-catalyst/support within Fenton-like system.

Selective oxidation of emerging contaminants by high-valent cobalt(IV)-Oxo species: Constructing high-spin Co(III) sites in Fenton-like system

In this study, a novel strategy for selectively generating Co(IV)=O species during peroxymonosulfate (PMS) activation was proposed, utilizing an optimized Co4Cu1-layered double hydroxide (LDH) material with low-coordination and high-spin-state Co sites. The incorporation of Cu(II), influenced by the Jahn-Teller effect, altered the geometry and coordination at Co(III) sites, optimizing the filling of Co 3d orbitals. The Co4Cu1-LDH/PMS system demonstrated exceptional catalytic activity for degrading emerging contaminants (ECs) across various water matrices, with a high concentration of Co(IV)=O generation. Continuous flow experiments showed an average 97.51 % degradation over 10 hours, indicating significant practical potential. Mechanistically, enhanced performance was attributed to a single electron transfer process and optimized orbital configurations for oxygen ligands at Co(III) sites. This study offers both theoretical insights and practical guidance for developing efficient catalysts targeting Co(IV)=O species in Fenton-like systems.

Bio-MIL-100(Fe) Heterostructure Construction and Charge Regulation: Iron Redundancy Breakthrough in a Fenton-like System

Bio-MIL-100(Fe) Heterostructure Construction and Charge Regulation: Iron Redundancy Breakthrough in a Fenton-like System

Surface and morphology modulated adsorption-activation of trace concentration hydrogen peroxide with multiple electron transfer pathways and sustained Fenton reactions

To promote mass transfer and activation of hydrogen peroxide (H2O2) in Fenton-like reactions, a novel MOFs-derived Fe2O3 was tailor-designed through surface sulfur modification and morphology tuning for degrading a group of persistent micropollutants, i.e., sulfamethoxazole, enrofloxacin, and ofloxacin. The introduction of Ca2+ and Mg2+ modulated the growth of crystal clusters to prevent aggregation of Fe2O3 nanoparticles and provide more reaction sites. Likewise, the abundant acid sites (–SO3H) promote the chemisorption of even trace-concentration H2O2 (S–O bonding), whereas the S–Fe bonding accelerates electron transfer to promote the Fe3+/Fe2+ cycle and thus the H2O2 utilization. More interestingly, surface-adsorbed H2O is found to be activated to form •OH, due to electron-poor Fe sites formed after detachment of –SO3H, demonstrating a sustained radical yield for the micropollutant degradation. This study opens new perspectives in catalyst design to ultimately realize the utilization of trace-concentration H2O2 and even H2O in Fenton-like systems.

The Ascorbic Acid-Modified Fenton System for the Degradation of Bisphenol A: Kinetics, Parameters, and Mechanism

Bisphenol A (BPA) has been extensively used in the commercial production, especially the production of plastic products. It has endocrine-disrupting effects and poses potential risks to health, which is also related to the development of various diseases. Nevertheless, using conventional biological treatment techniques has proved challenging in fully breaking down this particular hazardous substance. The degradation ability of the target substance was explored by investigating the effect of an ascorbic acid (Vc)-modified Fenton-like system. The results showed that the degradation rate of the modified system reached 74.6% after 20 min, which was much higher than the 9.1% degradation rate without Vc. Under different ratios of Vc and Fe(III), when the ratios were 1:1 and 1/2:1, the reaction efficiency was the best, and the degradation rate exceeded 83%. When pH = 6.5 and the ratio of Vc to Fe(III) was 1:1, the optimal conditions were achieved, and 83.5% of the BPA could be degraded within 60 min. The results of the quenching experiment provided evidence that •OH was the main reactive oxidizing species (ROS). Analysis of the BPA degradation pathway and the product toxicity evaluation revealed a reduction in the acute/chronic toxicity of BPA from toxic/very toxic to non-harmful/harmful levels. The presented evidence demonstrates that Vc significantly enhances the performance of the modified Fenton-like system and has definite potential for application.

Artificial humic acid mediated Fe(II) regeneration to restart Fe(III)/PMS for the degradation of atrazine

The degradation efficiency of organic contaminants using Fenton-like system based on Fe(II) and peroxymonosulfate (PMS) has been hindered by the rapid transformation from Fe(II) to Fe(III) and the slow regeneration of Fe(II). To address this challenge, artificial humic acid (AHA) derived from biomass was incorporated into Fe(III)/PMS system to build AHA/Fe(III)/PMS system. The results demonstrated that the degradation rate of atrazine (ATZ) in AHA/Fe(III)/PMS system (98.83%) is significantly superior to those in Fe(III)/PMS (16.51%) and AHA/PMS system (41.76%) within 90 min. Furthermore, Fe(II) measurement experiments revealed that AHA exhibited more significant iron-reducing potential. The analysis of FTIR, 3D-EEM, and liquid NMR indicated that AHA possessed more structures with reductive potential in comparison to commercial humic acid (CHA) and humic acid extracted from lignite (LHA). The results of persistent free radicals indicated that CHA possessed oxidative potential, which also accounted for the lowest Fe(II) concentration in those system containing CHA. Furthermore, quenching experiments, EPR analysis, and PMSO probe analysis have indicated the presence of reactive species such as •OH, SO4•-, and Fe(IV) within AHA/Fe(III)/PMS system. The degradation products from ATZ were identified and determined to exhibit reduced toxicity relative to parent compound. Collectively, these findings presented an in-depth understanding to reactivate Fe(III)/PMS system, offering a promising alternative strategy for efficient degradation of organic pollutants in water treatment processes.

Mechanistic insights into the pH-driven radical transformation of the Fe(II)/nCP in groundwater remediation

Calcium peroxide nanoparticles (nCP) as a versatile and safe solid H2O2 source, have attracted significant research interst for their application potential in groundwater remediation. Compared to the traditional Fenton system, the nCP-based Fenton-like system has a wider pH-working window for contaminants degradation. This results from the dominant radical transformation under different pH. Unlike the traditional Fenton system which is only effective in acid conditions with hydroxyl radical (•OH) as the main active species, the release of H2O2 and O2 from nCP provides multiple contaminants degradation pathways. In acidic environments, •OH and Fe(IV) predominate as the active species, facilitated by substantial H2O2 production which activates the Fenton reaction. In neutral or alkaline conditions, the production of H2O2 was dramatically decreased. While the O2 released from nCP can be catalyzed by Fe(II) to form superoxide radical (•O2-), which subsequently generate singlet oxygen (1O2). The formation pathway of •O2- was tracked by O18 isotope labeling experiment. The impact of the water matrix on radical generation in the Fe(II)/nCP Fenton-like system was also studied. This research deepens the understanding of the radical formation mechanisms in nCP-based Fenton-like system, offering insights to support their application in remediating contaminated groundwater.

OXIDATIVE DESTRUCTION OF AMOXICILLIN IN PHOTO-FENTON-LIKE OXIDIZING SYSTEM USING SOLAR IRRADIATION

The kinetic regularities of oxidative destruction of β-lactam penicillin antibiotics are studied using amoxicillin as example in Fenton-like iron-persulfate system under solar irradiation. The effect of Fe2+ and persulfate concentrations on the antibiotic degradation rate and mineralization in terms of total organic carbon (TOC) decay in combined {Solar/Fe2+ /S2O82-} system was examined. With the increase of oxidant concentration from 0.5 mM to 1.5 mM, the initial reaction rate of amoxicillin degradation increased to 2.5-fold, and the conversion of target compound and TOC mineralization reached 90% and 19%, respectively, after 120 min of solar exposure. Increasing the Fe2+ concentration from 0.1 mM to 0.3 mM resulted in a 1.5-fold increase in the initial reaction rate of amoxicillin oxidation and up to 21% for TOC mineralization. A comparative evaluation of different oxidizing systems was given. It was experimentally established that the efficiency of amoxicillin destruction process increases in the order: {S2O82-} < {Solar} < {Solar/S2O82-} < {Fe2+/S2O82-} < < {Solar/Fe2+/S2O82-}. It should be noted that TOC mineralization was observed only in combined {Solar/Fe2+/S2O82-} system, which indicates to deep oxidation of intermediates and, consequently, increasing biodegradability of the final reaction products. It was found that in the real water matrix, in the natural surface water of Selenga River, inhibition of amoxicillin degradation and TOC mineralization were observed, due to a greater extent to bicarbonate ions presented in it. The obtained results demonstrate the prospect of using solar irradiation for effective degradation of β-lactam penicillin antibiotics in the combined {Solar/Fe2+/S2O82-} oxidation system. For citation: Alekseev K.D., Sizykh M.R., Batoeva A.A. Oxidative destruction of amoxicillin in photo-fenton-like oxidizing system using solar irradiation. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 12. P. 123-130. DOI: 10.6060/ivkkt.20246712.7082.

Constructing Tandem Fenton-like Reaction Systems Based on Structure Adaption to Boost Water Contaminant Mineralization Efficiency.

Mineralization of emerging contaminants by using advanced oxidation processes (AOPs) is a desirable option to ensure water safety, but still challenged by the excessive chemical and/or energy input. Here, we conceptually proposed the tandem reaction system (TRS) of different reactive oxygen species (ROS) based on structure adaption of target contaminants. To construct a model TRS, we first realized highly selective generation of three classical ROS (1O2, HO⋅ and SO4⋅-) by peroxymonosulfate activation in an electrochemical Fenton-like system, where three replaceable Fe-centered cathodes were rationally designed as electronic mediator. The 1O2+SO4⋅--TRS exhibited nearly 100 % mineralization of sulfamethoxazole (SMX), whereas only 34.2 %, 56.2 % and 60.8 % for each of the single 1O2/HO⋅/SO4⋅--AOP systems. Mechanism exploration of SMX degradation in TRS evidenced that the initial reaction with 1O2 selectively destructed the sulfonamide bridge of SMX to form p-aminobenzenesulfonic acid, which will be vulnerable to sequent SO4⋅- attack to facilitate mineralization. Successful extendibility of 1O2+SO4⋅--TRS to other sulfonamide antibiotics and 1O2+HO⋅-TRS to phenolic and arylcarboxylic compounds, as well as the demonstration of 1O2+SO4⋅--TRS in treatment of three actual pharmaceutical wastewaters strongly support that TRS is a powerful and sustainable strategy to enhance the mineralization of emerging contaminants in water.

Hydrochar supported strategy for nZVI to remove bisphenol A and Cr(VI): Performance, synergetic mechanism, and life cycle assessment

To comprehensively overcome the shortcomings and extend the application of nanoscale zero-valent iron (nZVI), a promising hydrochar supported strategy was provided. nZVI/Eupatorium adenophorum hydrochar (nZVI/EaHC) composite was attained under relatively mild reaction condition, and life cycle assessment revealed that the greenhouse gases emission, ecotoxicity, and resource consumption of nZVI/EaHC fabrication processes largely reduced in comparison with nZVI and pyrolysis biochar supported nZVI (nZVI/EaBC). Moreover, nZVI/EaHC exhibited an outstanding potential in reduction and immobilization of Cr(VI) as well as degradation of bisphenol A (BPA) via Fenton-like system. The static experiment showed that the removal efficiency achieved 99.21 % within 1 h for Cr(VI) and 97.9 % within 1 min for BPA, which significantly exceeded the performance of nZVI/EaBC, accompanied by a significant detoxification to non-harmful level and mineralization of 87.9 % within 10 min. The dynamic continuous flow column experiment indicated that 90 % Cr(VI) was removed within 40 min and 90 % BPA within 180 min under ultra-low-dosage of catalyst and H2O2. Furthermore, hydrochar supported strategy may reduce the economic cost and avoid secondary pollution due to the outstanding stability under aerobic condition and recyclability in magnetic field. The synergetic mechanisms were further revealed, the abundant oxygen-containing functional groups on EaHC facilitated the generation of electron-rich/poor centers via chemical bond bridge (COFe) and Fe-π interaction, which further enhanced the electron transfer to reduce Cr(VI) or promote the production of multiple reactive species including OH, O2–, and 1O2 to degrade BPA, additionally, persistent free radicals on EaHC also contributed to the degradation of BPA. Therefore, this efficient, applicable, and sustainable strategy may have a greatly practical outlook on nZVI application together with a comprehensive control and utilization of biomass including invasive plants.

Slow-release of hydrogen peroxide from PDA-coated calcium peroxide for enhanced dye wastewater decolourisation removal

In Fenton-like systems, a slow-release of hydrogen peroxide (H2O2) is of great value in improving the sustainable treatment of pollutants. In this study, calcium peroxide (CaO2) was first synthesized by different methods, and its slow-release performance of H2O2 was evaluated. Then CaO2@PDA composites (referred to as CP-X, X represent the mass ratio of Polydopamine (PDA) to CaO2 were prepared by using a simple precipitation method. And the H2O2 slow-release experimental result indicates that the average release rate of the prepared CP-1.0 is 0.19 mmol·g-1·min-1 within 130 min. The release of H2O2 from CP-1.0 is consistent with the biexponential biphasic kinetic model, where water molecules and H2O2 osmotic diffusion are the main factors affecting the rate of H2O2 release. Decolourisation removal of crystalline violet (CV) solution was carried out using CP-1.0 as oxidants. Under the conditions of 0.02 g CP-1.0, pH = 6.5, and 20°C, more than 98.0% of CV solution (30 mg/L) was removaled within 30 min. Then, possible degradation pathways were postulated using a combination of density functional theory (DFT) and liquid chromatography mass spectrometry (LC-MS). Finally, the decolourisation degradation mechanism was proposed according to the active species quenching experiments and Electron Paramagnetic Resonance (EPR) analysis. This study presents novel insights into the removal of emerging pollutants in aqueous media by CaO2-based Fenton-like systems.

Oxidative degradation of chitosan by Fe-MCM-41 heterogeneous Fenton-like system

We herein disclosed an efficient multiphase Fenton-like catalytic system for oxidative degradation of chitosan. By utilizing Fe-MCM-41, featured with regular mesoporous structure and high specific surface area, the activation efficiency of H2O2 was significantly enhanced and the chitosan degradation efficiency proved by 28.1% higher than the conventional system using H2O2 alone. Under optimized conditions (5 g/L chitosan, 0.5 g/L Fe-MCM-41, 0.16 mol/L CH3COOH, 0.86 mol/L H2O2, 50 °C, 140 min), the viscosity reduction rate of chitosan reached an impressive 98.2%. Among the catalysts tested, Fe-MCM-41 with a loading factor of x = 0.12 demonstrated optimal degradation performance. After four recycles, the degradation efficiency maintained > 93.6%, demonstrating its excellent stability and recyclability for potential industrial applications. Kinetic studies provided further elucidation of the reaction mechanism, which indicated that the degradation process of chitosan followed a first-order kinetic model, with an apparent activation energy (Ea) of 48.91 kJ/mol. This novel and efficient strategy for chitosan degradation, addressed the challenges of catalyst recovery and secondary pollution typically associated with traditional Fenton systems, and posed broad application potential for polysaccharide material processing.

Heterogeneous Fenton system driven by magnetic graphene-like biochar for degrading tetracycline

In this study, a novel catalyst with high efficiency and low cost was synthesized from farmland waste peanut shells by one-step pyrolysis modification method via K2FeO4, and employed for the catalytic degradation of tetracycline (TC). The magnetic potassium ferrate modified graphene-like biochar catalyst (PFGB) exhibited a high porosity, a highly graphitized structure, and a large specific surface area (857.09 m2 g−1) which was almost 30 times higher compared with peanut shell biochar, and were found to contain more functional groups. The formation and distribution of Fe3O4 and Fe0 nanoparticles on the surface/pores of PFGB provided more active sites for promoting adsorption and catalytic degradation reactions, and accelerated Fe(II)/Fe(III) recycle. Under the optimal conditions (pH = 3.5, catalyst dosage = 0.5 g L−1, H2O2 concentration = 10 mmol L−1), about 98 % of TC were degraded within 90 min when the initial concentration of TC was 150 mg L−1, and PFGB could perform effectively over a wide pH range of 3–6. Furthermore, PFGB exhibited the advantages of convenient magnetic separation and strong reusability, maintaining a TC removal rate of ∼90 % after five cycles of experiments. The results of free radical quenching experiment and electron spin resonance analysis revealed that •OH and 1O2 were the main active species in the radical and non-radical pathways, respectively. This study indicated that PFGB, a catalyst developed for heterogeneous Fenton-like systems, possessed high efficiency, stability and reusability, and could be promising for the removal of TC in wastewater and other polluted waters.

Turning Microenvironments of Porous Co─N─C Catalysts Enable Efficient Fenton-Like Reaction.

Metal nitrogen carbon (MNC)-based Fenton reactions leveraged with robust peroxymonosulfate (PMS) interaction effectively guarantee the elimination of refractory contaminants, yet the precise design of local microenvironment of MNC to couple with the multiple PMS activation pose major challenges. Herein, a porous Co single-atom catalyst (SAC) with nitrogen defects (Nv) (MCo/NC-6) is fabricated to initiate PMS oxidation reaction. The weaker but richer coordination between Co and N in the precursor facilitates the formation of Nv and porous structure during pyrolysis, achieving simultaneously electronic structure and spatial distribution tuning. Compared with the Co SAC (ZCo/NC-6), the optimized MCo/NC-6 significantly increase the bisphenol A (BPA) reactivity (k = 0.63 min-1), PMS utilization (78%), and singlet oxygen (1O2) yield (100%) by 15.3, 2.4, and 2.6 times, respectively. Experimental analyses and theoretical calculations reveal that the Co─N─C coordination regulated by both micro space and neighboring Nv is endowed high-mobility electrons, thus synergistically facilitating rapid generation and efficient utilization of 1O2. This work promises new opportunities for the design of local microenvironments-regulated SACs, and charts new trajectories in complex Fenton-like systems.

Construction of a multiple reactive species-mediated Co9S8/NBC-PMS Fenton-like system for tetracycline degradation with broadened adaptability to water background

A Fenton-like system based on peroxymonosulfate (PMS) oxidant has high potential for antibiotic degradation, However, various complex water background factors, including pH, coexisting ions, and dissolved organic matter, can adversely affect degradation efficiency. This work constructed a PMS oxidative Fenton-like system activated by cobalt polysulfide/N-doped biochar composite (Co9S8/NBC) for the degradation of tetracycline (TC) and achieving approximately 99 % removal of TC. Furthermore, the removal efficiency was maintained above 90 % across a broad pH range (3−11), in the presence of various coexisting anions (Cl−, NO3− and CO32−), even at high concentrations of humic acid. The characterization of Co9S8/NBC through various techniques confirmed that Co9S8 nanoparticles were uniformly loaded within the porous NBC structure. Electron paramagnetic resonance and reactive oxygen species (ROSs) quenching experiment revealed that the effectiveness of TC degradation in the Co9S8/NBC/NBC-PMS system arises from the cooperation of radical and non-radical species rather than the single mechanism. Moreover, the analysis of the contribution ratios of ROSs to TC degradation indicates that the contribution of non-free radicals exceeds that of free radicals, and it is capable of adapting to changes in pH. The characterization of the post-reaction catalyst suggested that Co9S8 and NBC synergistically participated in the activation of PMS. Moreover, the practical examination proved that the disabled Co9S8/NBC catalyst can recover the catalytic activity via a reheat treatment, the leaching concentration of Co ions was lower than the emission limit of China. The river water and lake water as the matrix water have little negative impact on the degradation of TC. The Co9S8/NBC-PMS system is expected to provide a practical pathway for the treatment of antibiotic wastewater.

Degradation kinetics, influencing factors, and mechanisms of polycyclic aromatic hydrocarbons in a Fe3O4-nZVI Fenton-like system

To improve the catalytic performance of nano zero-valent iron (nZVI) in a Fenton-like system, Fe3O4 supported nZVI (Fe3O4-nZVI) was produced by the liquid-phase reduction method and co-precipitation method, then characterized by SEM, EDS, XRD, XPS, and VSM. Fe3O4-nZVI was used as the catalyst in a Fenton-like system to degrade polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (Nap), phenanthrene (Phe), and pyrene (Pyr) in simulated wastewater. The results showed that under the optimization conditions, which were 25℃, 0.6g/L of Fe3O4-nZVI dosage, 3 of the pH in the reaction system, and 10-15mmol/L of the concentration of H2O2, the sequence of degradation efficiency in this system was Phe (99.76%)>Pyr (99.71%)>Nap (98.01%). The reused experiments on Fe3O4-nZVI showed that the degradation efficiency for PAHs remained above 87% after 4 reuses of Fe3O4-nZVI. These results indicated that nanoscale magnetic composites of Fe3O4-nZVI had excellent reactivity, stability, and reuse performance. The fitting parameters of kinetics showed that the degradation of PAHs in the Fenton-like system with the Fe3O4-nZVI catalyst fitted well with the Behnajady-Modirshahla-Ghanbery kinetic model. The radial quenching experiment proved that ·OH was the dominant free radical for the degradation of PAHs in the Fe3O4-nZVI Fenton-like system. Based on the degradation products of PAHs and the related literature, the possible degradation paths of the three PAHs in the Fe3O4-nZVI Fenton-like system were inferred. The above results could provide a reference and basis for the treatment of wastewater containing PAHs by Fe3O4-nZVI Fenton-like technology.

Activation of persulfate by a layered double oxide supported sulfidated nano zero-valent iron for efficient degradation of 2,2′,4,4′-tetrabromodiphenyl ether in soil

The nano zero-valent iron (nZVI) activated persulfate (PS) is recognized as a promising approach to degrade 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), which is ubiquitous in the soil at electronic waste sites. However, all the reported studies were performed in liquids, gaps in the real behaviour and microbial contribution to the degradation of BDE-47 in soil media need to be urgently filled. The removal efficiency of BDE-47 is low using traditional nZVI as activator because of its aggregation and corrosion. Herein, we designed a novel layered double oxide supported sulfidated nano zero-valent iron (S-nZVI@LDO) composite and explored the performance of S-nZVI@LDO/PS to remediate BDE-47 contaminated soil. The results showed that S-nZVI@LDO has excellent stability and superior reduction capability. It could couple PS to achieve a rapid and efficient degradation of BDE-47, and the removal efficiency reached 92.31 % (5 mg/kg) within 6 h, which was much higher than that of n-ZVI/PS (53.38 %) or S-nZVI/PS (75.69 %). The kinetic constant of BDE-47 degradation by S-nZVI@LDO/PS was 23.6 and 3.7 times higher than that by single S-nZVI@LDO and nZVI/PS, respectively. It is attributable to the efficient production of SO4•-, •OH, O2•-, and 1O2 in the system, in which SO4•- and •OH dominated. The bioinformatic analysis demonstrate that soil remediation by S-nZVI@LDO/PS significantly enriched aromatic compounds-degrading bacteria and increased the abundance of hydrocarbon degradation functions. Microbial degradation may play important roles in the BDE-47 degradation and soil quality recovery. The identification of degradation pathways suggests that BDE-47 was degraded to very low-toxic products based on GHS toxicity prediction through a series process of debromination, hydroxylation, cleavage central oxygen, and ring opening, or even completely mineralized. The findings may provide significant implications for the in-situ clean-up of brominated flame retardants in contaminated soil using S-nZVI@LDO/PS Fenton-like system.

Highly efficient activation of peroxymonosulfate via KOH-activated Fe@NC for the degradation of bisphenol A.

In this study, the KOH-modified Fe-ZIF-derived carbon materials (Fe@NC-KOH-x) were designed for Fenton-like systems to enhance bisphenol A (BPA) removal from wastewater. Compared with the Fe@NC without KOH activation, the pore structure, BET (Brunner-Emmet-Teller) surface area, and oxygen-containing functional group of KOH-activated Fe@NC-KOH-x are dramatically improved, which increases the adsorption and catalytic performance. The Fe@NC-KOH-900/PMS system showed significant BPA removal reactivity across wide pH ranges and low doses of Fe@NC-KOH-900. Interestingly, our findings indicated that the removal effectiveness of BPA improved when PMS was introduced following the saturation adsorption of Fe@NC-KOH-x, as compared to the simultaneous introduction of Fe@NC-KOH-x and PMS. More particularly, through regression analysis, we found that the proportion of reactive species in the Fe@NC-KOH-x/PMS system changes with the increase of pyrolysis temperature, and there was a certain relationship between structure-function and active species in the Fe@NC-KOH-x/PMS system. O-C = O, Fe-N4, C-O, and pyrrolic N in Fe@NC-KOH-x lead to the generation of •OH, and SO4-•, C = O, Fe-N4, and defect are closely related to FeIV = O, and the formation of 1O2 is affected by Fe-N4, graphite N, C = O, and defect. Also, the density functional theory (DFT) calculation and the potential correlation between catalyst active centers and reactive oxygen species indicate that Fe-N4 is the main active site of Fe@NC-KOH-x. These outcomes of the study offer an innovation for enhanced elimination of BPA in wastewater treatment and provide a dynamic understanding of the mechanism of BPA degradation.