Sulfamethoxazole Degradation Rate Research Articles

A novel integrated microbial fuel cell-membrane bioreactor (MFC-MBR) for controlling the spread of antibiotic and antibiotic resistance genes while simultaneously alleviating membrane fouling

The dissemination of antibiotics and antibiotic resistance genes (ARGs) in the environment can potentially pose risks to ecosystems and human health. Herein, a novel microbial fuel cell and membrane bioreactor (MFC-MBR) integrated system characterized by internal reflux of sludge mixtures was proposed to reduce antibiotics, control the spread risk of antibiotic resistance genes (ARGs), and simultaneously alleviate membrane fouling. The bioelectricity production was distinctly promoted with increasing return flow ratios under sulfamethoxazole (SMX) addition. Besides, reactors characterized by higher return flow ratios achieved a relatively elevated degradation rate of SMX, attributed to the enhanced microbial activities through electrical stimulation. Importantly, the absolute abundance of intI1, sul1 and sul3 significantly decreased in the effluent of reactors characterized by higher return flow ratios. The value of zeta potential and particle size of sludge flocs subsequently increased and the content of membrane foulants dropped with the increasing return flow ratios. Moreover, MFC-MBRs characterized by higher return flow ratios were enriched in antibiotic degrading bacteria (Firmicutes, Thauera) and electrochemically active bacteria (Proteobacteria, Bacteroidota). Therefore, this study provided a theoretical basis for reducing the spread of antibiotics and ARGs while simultaneously alleviating fouling, achieving the best of both worlds, through the novel MFC-MBR integrated system.

The Degradation of Sulfamethoxazole via the Fe2+/Ultraviolet/Sodium Percarbonate Advanced Oxidation Process: Performance, Mechanism, and Back-Propagate–Artificial Neural Network Prediction Model

The degradation of sulfamethoxazole (SMX) via the Fe2+/Ultraviolet (UV)/sodium percarbonate (SPC) system was comprehensively investigated in this study, including the performance optimization, degradation mechanism, and predicting models. The degradation condition of SMX was optimized, and it was found that appropriate amounts of CFe2+ (10~30 μM) and CSPC (10 μM) under an acidic condition (pH = 4~6) were in favor of a higher degradation rate. According to probe compound experiments, it was considerable that ∙OH and ∙CO3− was the primary and subordinate free radical in SMX degradation, and k∙OH,SMX maintained two times more than that of k∙CO3−,SMX, especially under acidic conditions. The UV direct photolysis and other active intermediates were also responsible for the SMX degradation. These active intermediates were produced via the Fe2+/UV/SPC system, involving ∙HO2, HCO4−, ∙O2 −, or 1O2. Furthermore, when typical anions co-existed, the degradation of SMX was negatively influenced, owing to HCO3− and CO32− possibly consuming ∙OH or H2O2 to compete with SMX. In addition, the prediction model was successfully established via the back-propagate artificial neural network (BP-ANN) method. The degradation rate of SMX was well forecasted via the Back-Propagate–Artificial Neural Network (BP-ANN) model, which was expressed as Ypre=tanh(tanh(xiWih)Who). The BP-ANN model reflected the relative importance of influence factors well, which was pH > t > CFe2+≈CSPC. Compared to the response surface method Box–Behnken design (RSM-BBD) model (R2 = 0.9765, relative error = 3.08%), the BP-ANN model showed higher prediction accuracy (R2 = 0.9971) and lower error (1.17%) in SMX degradation via the Fe2+/UV/SPC system. These findings help us to understand, in-depth, the degradation mechanism of SMX; meanwhile, they are conducive to promoting the development of the Fe2+/UV/SPC system in SMX degradation, especially in some practical engineering cases.

Autotrophic degradation of sulfamethoxazole using sulfate-reducing biocathode in microbial photo-electrolysis system

Sulfamethoxazole is a representative of sulfonamide antibiotic pollutants. This study aims to investigate the degradation pathways of sulfamethoxazole and the response of microbial communities using the autotrophic biocathode in microbial photo-electrolysis systems (MPESs). Sulfamethoxazole with an initial concentration of 2 mg L−1 was degraded into small molecule propanol within 6 h with the biocathode. Elemental sulfur (S0) was detected in the cathode chamber, accounting for 57 % of the removed sulfate. The conversion from sulfate to S0 indicated that autotrophic microorganisms might adopt a novel pathway for sulfamethoxazole removal in the MPES. In the abiotic cathode, sulfamethoxazole degradation rate was 0.09 mg L−1 h−1 with the electrochemistry process. However, sulfamethoxazole was converted to products that still contain benzene rings, including p-aminothiophenol, 3-amino-5-methylisoxazole, and sulfonamide. The microbial community analysis indicated that the synergistic interaction of Desulfovibrio and Acetobacterium promoted the autotrophic degradation of sulfamethoxazole. The results suggested that autotrophic microorganisms may play an important role in the environmental transformation of sulfamethoxazole.

Converting peracetic acid activation by Fe3O4 from nonradical to radical pathway via the incorporation of L-cysteine

Recently, peracetic acid (PAA) based Fenton (-like) processes have received much attention in water treatment. However, these processes are limited by the sluggish Fe(III)/Fe(II) redox circulation efficiency. In this study, L-cysteine (L-Cys), an environmentally friendly electron donor, was applied to enhance the Fe3O4/PAA process for the sulfamethoxazole (SMX) abatement. Surprisingly, the L-Cys incorporation was found not only to enhance the SMX degradation rate constant by 3.2 times but also to switch the Fe(IV) dominated nonradical pathway into the •OH dominated radical pathway. Experiment and theoretical calculation result elucidated -NH2, -SH, and -COOH of L-Cys can increase Fe solubilization by binding to the Fe sites of Fe3O4, while -SH of L-Cys can promote the reduction of bounded/dissolved Fe(III). Similar SMX conversion pathways driven by the Fe3O4/PAA process with or without L-Cys were revealed. Excessive L-Cys or PAA, high pH and the coexisting HCO3−/H2PO4− exhibit inhibitory effects on SMX degradation, while Cl− and humic acid barely affect the SMX removal. This work advances the knowledge of the enhanced mechanism insights of L-Cys toward heterogeneous Fenton (-like) processes and provides experimental data for the efficient treatment of sulfonamide antibiotics in the water treatment.

Cu Distribution Pattern Controlled Active Species Generation and Sulfamethoxazole Degradation Routes in a Peroxymonosulfate System

The distribution pattern of metals as active centers on a substrate can influence the peroxymonosulfate (PMS) activation and contaminants degradation. Herein, atomic layer deposition is applied to prepare Cu single atom (SA-Cu), cluster (C-Cu), and film (F-Cu) decorated MXene catalysts by regulating the number of deposition cycles. In comparison with SA-Cu-MXene (adsorption energy (Eads) = −4.236 eV) and F-Cu-MXene (Eads = −3.548 eV), PMS is shown to adsorb preferably on the C-Cu-MXene surface for activation (Eads = −5.435 eV), realizing higher utilization efficiency. More SO4− are generated in C-Cu-MXene/PMS system with steady-state concentration and 1–3 orders of magnitude higher than those in the SA-Cu-MXene and F-Cu-MXene activated PMS systems. Particularly, the contribution of SO4− oxidation to sulfamethoxazole (SMX) degradation followed the order, C-Cu-MXene (97.3%) > SA-Cu-MXene (90.4%) > F-Cu-MXene (71.9%), realizing the larger SMX degradation rate in the C-Cu-MXene/PMS system with the degradation rate constants (k) at 0.0485 min−1. Additionally, SMX degradation routes in C-Cu-MXene/PMS system are found with fewer toxic intermediates. Through this work, we highlighted the importance of guided design of heterogeneous catalysts in the PMS system. Appropriate metal distribution patterns need to be selected according to the actual water treatment demand. Metal sites could be then fully utilized to produce specific active species to improve the utilization efficiency of the oxidants.

Role of nitrogen dual reaction sites in N-doped graphene aerogels for synergistic sulfamethoxazole adsorption and peroxymonosulfate activation in Fenton-like process

Persulfate-based advanced oxidation technology is widely used in water treatment, and the key is to develop catalysts showing excellent performance. In this study, an N-doped graphene aerogel (N-GA-2) with a three-dimensional macroscopic structure was prepared by chemically reducing graphene oxide using ethylenediamine (EDA) and was used to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) degradation. N-GA-2 has high pyridinic N content (5.84 at.%), and shows excellent catalytic performance in the activation of PMS. The SMX degradation rate was 94.11% within 90 min, and the first-order reaction rate constant was 0.0231 min−1. Furthermore, the adsorption of SMX on N-GA-2 was chemisorption, and the maximum adsorption capacity (qm) was 250.00 mg/g. Quenching experiments and electrochemical tests confirmed that the electron-transfer pathway was the main reason for SMX degradation. X-ray photoelectron spectroscopy and density functional theory revealed that pyridinic N, adjacent C atoms and electron-rich C = O functional groups were involved in the degradation of SMX. Specially, pyridinic N functioned as dual reaction sites for both SMX adsorption and PMS activation. The formation of SMX/N-GA-2* and N-GA-2/PMS* complexes, dominated by pyridinic N, enabled the completion of electron-transfer pathways. In addition, N-GA-2/PMS/SMX system demonstrated superior continuous catalytic performance in fluidized-bed experimental facility simulating practical applications, which can stably and sustainedly degrade SMX. This study focuses on the mechanism of electron transfer pathway induced by nitrogen dual reaction site in N-doped graphene aerogel and explores its potential application in engineering. This will provide basic theoretical support for the practical application of N-GA-2/PMS catalytic system.

Photo-Fenton properties of MIL-88A(Fe) / Ti3C2 MXene with tunable active crystal facets: Universal for degradation of common pollutants in wastewater

In this study, the MIL-88A(Fe)/MXene Type-I heterojunction photocatalysts were successfully prepared. The active crystal plane of MIL-88A(Fe) was modulated by changing the solvent ratio used in the solvent-thermal reaction. Taking sulfamethoxazole as the main target pollutant, the effects of different morphologies of MIL-88A(Fe) and different loadings of MXene on the photocatalytic performance of the composite were discussed in detail. The results showed that the degradation rate of sulfamethoxazole by DA-M100 composite photocatalysis combined with Fenton effect could reach about 70% within 10 min of light exposure, and the degradation efficiency reached 92.66% after 60 min of light exposure. The universality test showed that DA-M100 had good photo-Fenton oxidation ability for common dyes and good photo-Fenton reduction ability for heavy metal ions in sewage. After 1 h of irradiation, the removal efficiency of Cr (VI), Cu (II) and Ni (II) reached 95.88%, 79.77% and 66 67%, respectively. The stability experiments showed that DA-M100 had a good adaptability to the environment. The results of electrochemical experiments and photoemission spectroscopy showed that DA-M100 increased the migration rate of photogenerated electron-hole pairs and decreased their recombination rate. The results show that the complex of iron-based MOF and MXene has a good application prospect in the treatment of industrial wastewater, and also provides a new idea for the modification of Type-I heterojunction.

Catechin-enhanced sulfamethoxazole degradation in Fe(II) activated peracetic acid process: Efficiency, mechanism and affecting factors

Peracetic acid (PAA), a commonly used environmentally friendly disinfectant, has recently gained attention on its potential for degrading organic pollutants in water due to its high oxidation potential. A potential approach for enhancing the Fe(II)/PAA process was proposed in this study. The effect of catechin (CAT), a polyphenolic antioxidant, on Fe(II)/PAA system for the degradation of sulfamethoxazole (SMX) in water was investigated. The results showed that CAT significantly enhanced the degradation efficiency of Fe(II)/PAA against SMX. The SMX degradation rate improved from 39.2 % to 88.2 % in 60 min in the presence of CAT. CAT might serve as an effective reducing agent to quantitatively reduce Fe(III) to Fe(II) with a molar ratio of about 1:2.4 between CAT and Fe(III). Reactive species were fully identified. Hydroxyl radicals, organic radicals and FeIVO2+ might involve in the degradation of SMX. Affecting factors including reagent dose, pH and water matrices were investigated. Three possible degradation pathways of SMX were proposed based on the identified reaction products, underscoring its potential applicability in water treatment.

Effect of Benzophenone Type UV Filters on Photodegradation of Co-existing Sulfamethoxazole in Water

Benzophenones (BPs) frequently occur in water environments, and they are able to both screen UV light and to sensitize reactive intermediate (RI) production. However, BPs have largely been overlooked as a background water component when studying photodegradation of co-existing organic micropollutants (OMPs). Therefore, in this study, we investigated the influence of BP and its derivative oxybenzone (BP3) on the degradation of the co-existing model OMP sulfamethoxazole (SMX). A series of photodegradation experiments were conducted covering a range of BPs concentrations in μg/L levels, and the degradation of 1.00 μM of SMX was studied. The addition of BP at 0.10 μM, 0.25 μM, and 0.30 μM, and BP3 at 0.10 μM and 0.25 μM, significantly increased the first order degradation rate constant of 1.00 μM of SMX (kobs(BP)) by 36.2%, 50.0%, 7.3%, 31.5%, and 36.2% respectively, compared to that in the absence of any BPs. The maximum indirect photodegradation induced by BP and BP3 reached 33.8% and 27.7%, respectively, as a percentage of the observed SMX degradation rate at the [BPs]/[SMX] ratio of 0.25. In general, triplet excited dissolved organic matter (3SMX*, 3BP*, and 3BP3*) played the major role in the photosensitizing ability of BPs. The results further implied that the increase of SMX degradation at the molar ratio of 0.25 was possibly due to 3BP* for the mixture of SMX and BP. Overall, this study revealed the sensitizing ability of BP and BP3 on the co-existing OMP, SMX, in water for the first time. Our findings can be applied to other BP type UV filters which are similar to BP and PB3 in molecular structure.

Degradation of SMX with Peracetic Acid Activated by Nano Core-shell Co@NC Catalyst

Peracetic acid (PAA), as a new oxidant, has attracted increasing attention in the treatment of refractory organic pollution in sewage. In this study, the nano core-shell Co@NC catalyst was prepared via etching and used to activate PAA to degrade sulfamethoxazole (SMX) in sewage. The results indicated that the degradation rate of SMX reached 98%, and its reaction rate constant was 0.80 min-1 under optimal conditions (catalyst dosage=0.02 g·L-1, PAA concentration=0.12 mmol·L-1, pH=7, SMX concentration=10 μmol·L-1). With the increase in PAA concentration and core-shell Co@NC dosage, the degradation efficiency of SMX increased. The study found that the core-shell Co@NC/PAA system had the best degradation effect on SMX under near-neutral conditions (pH 6.0-8.0), and both acidic and alkaline environments were not conducive to SMX degradation. HCO3- and humic acid showed significant inhibition on the degradation of SMX, whereas Cl- showed weak inhibition. In addition, through a free radical quenching experiment and electron paramagnetic resonance (EPR) detection, acetoxy radical (CH3CO2CO3·) were the main active species for the degradation of organic pollutants in the system. Transformation products (TPs) of SMX were analyzed by U-HPLC-Q-Exactive Orbitrap HRMS, and a possible degradation path of SMX was proposed. At the same time, the catalyst recycling experiment showed that the nano core-shell Co@NC catalyst had good stability and reusability.

Dual role of soil-derived dissolved organic matter in the sulfamethoxazole oxidation by manganese dioxide

Manganese dioxide (MnO2) can mediate organic pollutant oxidation in aquatic environments, which has been reported to be inhibited or promoted by dissolved organic matter (DOM) in different studies. It remains unresolved why conflicting results have been observed and whether such results depend on the type and concentration of DOM. Here, we used three types of well-characterized DOM derived from soil heated at 50, 250, or 400°C (DOM_50, DOM_250, and DOM_400, respectively) to evaluate the impacts of DOM type and concentration and environmental pH on MnO2-mediated oxidation of sulfamethoxazole, a widely detected and ecotoxic emerging pollutant. We observed that the degradation rate of sulfamethoxazole was possibly promoted by DOM_250 (pH 6‒8), while it was generally inhibited by DOM_50 and DOM_400. Furthermore, it was initially inhibited and then promoted with increasing DOM concentrations and was consistently less inhibited at a higher pH. The inter-DOM variations of sulfamethoxazole degradation could be explained by the more enriched polyphenolics in DOM_250 than in DOM_50 and DOM_400, whereas the weak promoting effect of DOM_400 indicates that high DOM aromaticity may not necessarily promote pollutant degradation. Our results reconcile the debate on the role of DOM in the oxidation of sulfamethoxazole by MnO2 and highlight the decisiveness of the molecular composition and concentration of DOM and the reaction pH in the overall promoting or inhibiting role of DOM.

Sludge biochar as an electron shuttle between periodate and sulfamethoxazole: The dominant role of ball mill-loaded Mn2O3

In this study, a one-step solvent-free method using the ball milling technique was employed to prepare Mn2O3-loaded sludge biochar (BM-SBC/Mn2O3), and it was applied to the efficient activation of periodate (IO4−) to achieve rapid removal of sulfamethoxazole from the water column. A nearly two-fold improvement in the degradation rate of sulfamethoxazole (pseudo-first-order constants from 0.049 to 0.09 min−1) was achieved with only a small loading of Mn2O3 (the mass ratio of Mn2O3 and SBC was 1:6). The BM-SBC/Mn2O3 possessed excellent IO4− activation ability and achieved 95.3% removal efficiency of sulfamethoxazole within 30 min. The removal efficiency of sulfamethoxazole was maximized at an initial pH of 3 and was almost unaffected by the coexisting inorganic anions and humic acid. Mechanistic studies suggested that free radical (•OH) and non-radical pathways were collectively responsible for the removal of sulfamethoxazole, while the non-radical pathway of electron transfer was predominant. Ball milling loading of Mn2O3 improved the degree of defects in the catalyst and enhanced the electron transfer efficiency. This study advances the fundamental understanding of the underlying mechanisms involved in the process of IO4− activation catalyzed by ball milling loaded metal oxides onto sludge biochar.

Effects of Fe-Co@N-BC anode on degradation of sulfamethoxazole (SMX) in microbial fuel cells

Sulfamethoxazole (SMX), a common antibiotic, is commonly used to treat urinary tract infections and intestine infections caused by sensitive bacteria. Water pollution is exacerbated as a result of its abuse and discharge. The feasibility and advantage of using microbial fuel cells (MFC) to degrade sulfamethoxazole have been proved. However, MFC is limited in wastewater treatment due to low bioelectric catalytic efficacy and expensive electrode costs. In this research, high performance Fe-Co@N/BC anode materials were prepared by bimetal and N doping to improve the electrochemical performance and biocompatibility of the electrodes, and Fe-Co@N/BC anode MFC was applied to the degradation of SMX. The results show that the MFC of Fe-Co@N/BC anode has the lowest internal resistance (144.46 Ω), greatly improves the electrical performance, and the maximum degradation rate of SMX reaches 89.1 %, which is 2.1 times that of a conventional anaerobic reactor. The results show that Fe-Co@N/BC anode has good physicochemical properties and the Fe-Co@N/BC anode MFC reactor can effectively degrade SMX.

An economic, self-supporting, robust and durable LiFe5O8 anode for sulfamethoxazole degradation

Electrochemically activating peroxydisulfate (PDS) to degrade organic pollutants is one of the most attractive advanced oxidation processes (AOPs) to address environmental issues, but the high cost, poor stability, and low degradation efficiency of the anode materials hinder their application. Herein, an economic, self-supporting, robust, and durable LiFe5O8 on Fe substrate (Fe@LFO) anode is reported to degrade sulfamethoxazole (SMX). When PDS is electrochemically activated by the Fe@LFO anode, the degradation rate of SMX is significantly improved. It is found that hydroxyl radicals (•OH), superoxide radical (O2•–), singlet oxygen (1O2), Fe(Ⅳ), activated PDS (PDS*), and direct electron transfer (DET) reactions synergistically contribute to the degradation of SMX, which can realize the degradation of SMX in four possible routes: cleavage of the isoxazole ring, hydroxylation of the benzene ring, oxidation of the aniline group, and cleavage of the S–N bond, as evidenced by a series of tests of radicals quenching, electron paramagnetic resonance (EPR), linear sweep voltammetry (LSV) and liquid chromatograph mass spectrometer (LC-MS). Furthermore, Fe@LFO has good structural stability, excellent cyclability and low degradation cost, demonstrating its great potential for practical applications. This work contributes to a stable and effective anode material in the field of AOPs.

Ascorbic acid promoted sulfamethoxazole degradation in MIL-88B(Fe)/H2O2 Fenton-like system

In this work, the presence of ascorbic acid (AsA) in MIL-88B(Fe)/H2O2 system was demonstrated to significantly increase the sulfamethoxazole (SMX) degradation efficiency. The SMX degradation rate in AsA/MIL-88B(Fe)/H2O2 system was 0.177 L/(mg∙min), which was 60 times that of the MIL-88B(Fe)/H2O2 system. Moreover, the study shows that AsA not only promotes SMX degradation in Fenton-like systems but also expands its pH application range. The effect of coexisting anions on the catalytic performance of the AsA/MIL-88B(Fe)/H2O2 system was also investigated. Then, reactive species were detected via quenching experiments, which indicated •OH as the dominant free radical contributing to SMX degradation. Meanwhile, ESR determinations confirmed the existence of •OH and O2 − • in AsA/MIL-88B(Fe)/H2O2 system. The high activity of the AsA/MIL-88B(Fe)/H2O2 system was attributed to the effective surface Fe(III)/Fe(II) cycle promoted by AsA, and a possible mechanism of the AsA/MIL-88B(Fe)/H2O2 system is proposed. The possible pathways for SMX and AsA degradation in the AsA/MIL-88B(Fe)/H2O2 system are proposed based on the identified intermediates and the ecotoxicity analysis was conducted by ECOSAR. Finally, experimental results using the actual surface water and groundwater revealed the excellent availability of AsA/MIL-88B(Fe)/H2O2 system in remediating SMX contaminated water. This study presents a novel, efficient Fenton-like system using AsA and iron-based metal-organic frameworks for sulfonamide removal from water.

Degradation of sulfamethoxazole by chlorination in water distribution systems: Kinetics, toxicity, and antibiotic resistance genes

Sulfamethoxazole (SMX) is one of veterinary drugs and food additives, which has been frequently detected in surface waters in recent years and will cause damage to organisms. Therefore, SMX was selected as a target to be investigated, including the degradation kinetics, evolution of toxicity, and antibiotic resistance genes (ARGs) of SMX during chlorination in batch reactors and water distribution systems (WDS), to determine the optimal factors for removing SMX. In the range of investigated pH (6.3-9.0), the SMX degradation had the fastest rate at close to neutral pH. The chlorination of SMX was affected by the initial total free chlorine concentration, and the degradation of SMX was consistent with second-order kinetics. The rate constants in batch reactors are (2.23 ± 0.07) × 102 M-1 s-1 and (5.04 ± 0.30) × 10M-1 s-1 for HClO and ClO-1 , respectively. Moreover, the rate constants in WDS are (1.76 ± 0.07) × 102 M-1 s-1 and (4.06 ± 0.62) × 10M-1 s-1 , respectively. The degradation rate of SMX was also affected by pipe material, and the rate followed the following order: stainless-steel pipe (SS) > ductile iron pipe (DI) > polyethylene pipe (PE). The degradation rate of SMX in the DI increased with increasing flow rate, but the increase was limited. In addition, SMX could increase the toxicity of water initially, yet the toxicity reduced to the level of tap water after 2-h chlorination. And the relative abundance of ARGs (sul1 and sul2) of tap water samples was significantly increased under different chlorination conditions. PRACTITIONER POINTS: The degradation rate of SMX in batch reactor and WDS is different, and they could be described by first- or second-order kinetics. The degradation of SMX had the fastest rate at neutral pH. The degradation rate of SMX was also affected by pipe material and flow velocity. SMX increased the toxicity of water initially, yet the toxicity reduced after a 2-h chlorination. SMX increased the relative abundance of antibiotic resistance genes sul1 and sul2.

Synergistic activation of peroxymonosulfate by nickel-cobalt hexacyanoferrate derived hybrid metal oxides for efficient sulfamethoxazole degradation

The development of a heterogeneous catalyst for efficient activation of peroxymonosulfate (PMS) is still highly desired in metal-based advanced oxidation processes. In this study, nickel-cobalt-iron hybrid oxides (NiCoFe-HO) catalyst was fabricated via direct thermal decomposition of nickel-cobalt hexacyanoferrate to activate PMS for sulfamethoxazole (SMX) degradation. NiCoFe-HO presented a much greater catalytic performance in SMX degradation with PMS under neutral pH (k = 0.079 min−1). The degradation rate of SMX with NiCoFe-HO was 2.3 and 3.0 times higher than that with nickel-iron hybrid oxides and cobalt-iron hybrid oxides, respectively. The synergistic effect among Ni, Co and Fe was experimentally verified to elucidate the superior catalytic activity. Sulfate radical and singlet oxygen were identified as the predominant reactive species in the current oxidation process. SMX degradation efficiency was gradually enhanced with the increase of catalyst dosage, PMS dosage and temperature but decreased with the increase of pH. In addition, NiCoFe-HO showed good stability and reusability. This study extends the design of hybrid metal oxides as efficient heterogeneous catalysts for PMS activation.

Novel activated system of ferrate oxidation on organic substances degradation: Fe(VI) regeneration or Fe(VI) reduction

Ferrate(VI) oxidation has caught more attention because of its high-efficiency degradation capacity on organic substances, while previous studies overlooked the effect of NaClO and NaClO2 on Fe(VI) oxidizability. This study discovered that NaClO could react with intermediate iron species, i.e., Fe(V) and Fe(IV), to regenerate Fe(VI), which reduced the unnecessary consumption of Fe(VI) by its self decomposition and thus improved the oxidizability of ferrate(VI) on organic substances. Then, the degradation content of sulfamethoxazole (SMX) and carbamazepine (CBZ) increased from 60.77 % and 68.42 % of 50 μM of Fe(VI) group to 100 % and 73.21 % of Fe(VI)/NaClO (50/5 μM) system within 30 min, respectively. However, NaClO2 contributed to reducing Fe(VI) to form more intermediate iron species in the reaction system and then elevated the degradation rate of SMX and CBZ at the initial stage. NaClO2 also further reduced intermediate iron species, leading to the decrease of active species. Besides, OH was involved into organics degradation in Fe(VI)/NaClO2 system, due to the rapid decomposition of ferrate(VI). By frontier orbital theory analysis, Fe(VI) had the lowest ELUMO (-5.50 eV) so it was more liable to be reduced by NaClO2 than intermediate iron species. Alpha orbital of Fe(V) possessed the highest EHOMO (−7.36 eV), which was more prone to be attacked by NaClO. Two coupling systems still achieved a synergistic effect on SMX degradation in authentic water. Meanwhile, the acute toxicity and disinfection by-products (DBPs) was further decreased in coupling systems. Therefore, Fe(VI)/NaClO and Fe(VI)/NaClO2 system may be a viable method for abating micropollutants with their unique advantages in water treatment.

Catalytic pyrolysis of lotus leaves for producing nitrogen self-doping layered graphitic biochar: Performance and mechanism for peroxydisulfate activation.

In this study, nitrogen self-doping layered graphitic biochar (Na-BC900) was prepared by catalytic pyrolysis of lotus leaves at 900°C, in the presence of NaCl catalyst, for peroxydisulfate (PDS) activation and sulfamethoxazole (SMX) degradation. NaCl as catalyst played a crucial part in the preparation of Na-BC900 and could be reused. The SMX degradation rate in Na-BC900/PDS system was 12 times higher than that in un-modified biochar (BC900)/PDS system. The excellent performance of Na-BC900 for PDS activation was attributed to its large specific surface areas (SSAs), the enhanced graphitization structure and the high graphitic N content. The quenching and electrochemical experiments, electron paramagnetic resonance (EPR) studies inferred that the radicals included SO4•-, •OH, O2•- and the non-radical processes were driven by 1O2 and biochar mediated electron migration. Both radical and non-radical mechanisms contributed to the removal of SMX. Additionally, this catalytic pyrolysis strategy was clarified to be scalable, which can be applied to produce multiple biomass-based biochar catalysts for restoration of polluted water bodies.

Highly efficient peroxymonosulfate activation of single-atom Fe catalysts via integration with Fe ultrafine atomic clusters for the degradation of organic contaminants

Recently, Fe single-atom catalysts activating peroxymonosulfate (PMS) have been of great potential to degrade recalcitrant organic pollutants. However, the mechanism of the unfavorable metal agglomerates produced throughout high-temperature pyrolysis on the Fenton-like reaction still remains confused. Herein, an efficient and stable catalyst integrating Fe single atoms with ultrafine atomic clusters (FeUAC@FeSA-NC) was successfully synthesized. The FeUAC@FeSA-NC/PMS system exhibited nearly 100% sulfamethoxazole (SMX) decomposition performance over a broad range of pH 3.0–9.0. Considering the difference in SMX degradation rate with or without Fe ultrafine atomic clusters, the catalytic performance of leached Fe ions, and the permissible Fe leaching concentration, it was not necessary to acid leach the FeUAC@FeSA-NC catalyst before use. Density functional theory (DFT) calculations manifested that the isolated Fe single-atom site neighbored by ultrafine atomic clusters acted as the optimal active site for PMS activation, and simultaneously the pyrrolic N served as the SMX adsorption site. The reactive species, including 1O2, O2−, SO4− and OH radicals and activated metal-peroxo species (Fe-PMS*), played the key role in FeUAC@FeSA-NC/PMS system. The satisfactory SMX removal efficiency and mineralization rate in actual wastewater imply that this efficient heterogeneous catalytic PMS system is a promising approach for sustainable wastewater reclamation applications.