Degradation Of Sulfamethoxazole Research Articles

Degradation mechanism and decomposition of sulfamethoxazole aqueous solution with persulfate activated by dielectric barrier discharge.

The present study focused on the degradation of sulfamethoxazole (SMX) aqueous solution and the toxicity of processing aqueous by the dielectric barrier discharge (DBD) activated persulfate (PS). The effects of input voltage, input frequency, duty cycle, and PS dosage ratio on the SMX degradation efficiency were measured. Based on the results of the Response Surface Methodology (RSM), SMX degradation efficiency reached 83.21% which is 10.54% higher than that without PS, and the kinetic constant was 0.067 min-1 in 30 min when the input voltage at 204 V (input power at 110.6 W), the input frequency at 186 Hz, the duty cycle at 63%, and the PS dosage ratio at 5.1:1. The addition of PS can produce more active particles reached 1.756 mg/L (O3), 0.118 mg/L (H2O2), 0.154 mmol/L (·OH) in 30 min. Furthermore, the DBD plasma system effectively activated an optimal amount of PS, leading to improved removal efficiency of COD, and TOC to 30.21% and 47.21%, respectively. Subsequently, eight primary by-products were pinpointed, alongside the observation of three distinct pathways of transformation. Predictions from the ECOSAR software indicated that most of the degradation intermediates were less toxic than SMX. The biological toxicity experiments elucidated that the treatment with the DBD/PS system effectively reduced the mortality of zebrafish larvae caused by SMX from 100% to 20.13% and improved the hatching rate from 55.69% to 80.86%. In particular, it is important to note that the degradation intermediates exhibit teratogenic effects on zebrafish larvae.

Impact of Condition Variations on Bioelectrochemical System Performance: An Experimental Investigation of Sulfamethoxazole Degradation

Bioelectrochemical systems (BESs) are an innovative technology for the efficient degradation of antibiotics. Shewanella oneidensis (S. oneidensis) MR-1 plays a pivotal role in degrading sulfamethoxazole (SMX) in BESs. Our study investigated the effect of BES conditions on SMX degradation, focusing on microbial activity. The results revealed that BESs operating with a 0.05 M electrolyte concentration and 2 mA/cm2 current density outperformed electrolysis cells (ECs). Additionally, higher electrolyte concentrations and elevated current density reduced SMX degradation efficiency. The presence of nutrients had minimal effect on the growth of S. oneidensis MR-1 in BESs; it indicates that S. oneidensis MR-1 can degrade SMX without nutrients in a short period of time. We also highlighted the significance of mass transfer between the cathode and anode. Limiting mass transfer at a 10 cm electrode distance enhanced S. oneidensis MR-1 activity and BES performance. In summary, this study reveals the complex interaction of factors affecting the efficiency of BES degradation of antibiotics and provides support for environmental pollution control.

Interactive effects of urine components and treatment conditions on antibiotic degradation of combined system integrating thermally activated peroxydisulfate and membrane distillation using machine learning

The antibiotic degradation in urine is gaining focus as it’s essential for resource recovery. Complex organic and inorganic substances in urine impact degradation efficiency through their involvement in radical-type chain reactions. In this study, more than 95 % of sulfamethoxazole (SMX) in urine was successfully degraded in both concurrent and sequential modes of a combined system integrating thermally activated peroxydisulfate and membrane distillation (TAP-MD), previously shown to be effective for resource recovery. Three algorithms, including random forest (RF), XGBoost, and support vector machine (SVM), were applied to model the impact of urine components and treatment conditions on SMX degradation. The XGBoot and RF models, fine-tuned by Bayesian optimization, are accurate and credible in both prediction and interpretation (R2 > 0.90). The models suggest that the improvement of SMX degradation by the MD process is due to PDS enrichment, with high PDS concentrations significantly promoting SMX degradation. Urea and HCO3− are the key factors impacting SMX degradation efficiency, followed by temperature, PDS, Cl−, and NH4+. Additionally, strong interaction effects between urine components were found on SMX degradation, contrasting with results from individual ions that were present in isolation. At high urea concentration (>100 mM), increasing concentrations of Cl−, NH4+, and HCO3− significantly inhibited SMX degradation. As the second key factor on SMX degradation, HCO3− can react with S2O82− without producing free radicals, resulting in a reduction in its yield. Furthermore, in the presence of high concentrations of HCO3−, the Cl− and NH4+ negatively affect the kobs of SMX degradation. The HCO3− competes with SMX for Cl to produce the weak oxidant CO3∙−, which reacts quickly with NH2∙ without producing other free radicals, causing a loss of free radicals.

Tailoring the surface functional groups of biochar for enhanced adsorption and degradation of pharmaceutically active compounds

In this study, orange peel biochar (OPBC) was synthesized through a pyrolysis process. Decoration with two specific functional groups (i.e., –COOH and NH2) was performed through a ball milling-assisted modification process to yield the respective biochars (i.e., OPBC-COOH and OPBC-NH2). Both OPBC-COOH and OPBC-NH2 demonstrated excellent adsorption capacities for sulfamethoxazole (SMX) and carbamazepine (CBZ), and hydrogen bonding between the pharmaceuticals and BCs followed the primary adsorption mechanism. In addition, both OPBC-COOH and OPBC-NH2 (0.3 g/L) exhibited high degradation efficiencies for SMX (10 mg/L, 87 %; 92 %) and CBZ (10 mg/L, 73 %; 83 %) when peroxymonosulfate (PMS, 1 mM) was present. The scavenging experiments confirmed that electron transfer and radical/non-radical pathways (·OH and 1O2) are mainly responsible for the degradation of SMX and CBZ, respectively. It was also proven that the oxygen- and nitrogen-containing surface functional groups on BC are important for activating PMS for the degradation of organic pollutants. These findings provide new insights into the effects of functional groups on BC for the degradation of contaminants of emerging concern.

A sustainable electrochemical strategy utilizing pulsed alternating current and dual carbon felt electrodes for enhanced degradation of organic pollutants: Oxidation performance and mechanisms

In this work, a novel electrochemical (EC) oxidation system utilizing pulsed alternating current (PAC) and dual carbon felt (CF) electrodes has been established for sustainable degradation of sulfamethoxazole (SMX) with no addition of extra oxidant. The EC/PAC system showed high degradation efficiency and energy efficiency compared to the pulsed direct current (PDC) and direct current (DC) systems. The EC/PAC process was effective across a wide pH range of 3–11 for SMX removal. The results showed that the 1O2 confined to the CF electrode surface was the dominant oxidative specie that was generated from dissolved oxygen in the system. Under PAC conditions, the cathode and anode were rapidly switched on the same CF electrode, increasing the generation of 1O2 for enhanced SMX oxidation. Furthermore, the EC/PAC system demonstrated resistance to interference from various anions of different concentration levels found in natural environment. In contrast to the EC/PDC system, the EC/PAC system emerged as a promising option for more efficient H2O2 production. High-resolution mass spectrometry results revealed the SMX degradation pathways and byproducts, which were then evaluated for toxicity removal. Overall, the EC/PAC system offers a green and sustainable solution to future wastewater treatment, with high degradation rates, energy efficiency, and sustainability.

Novel insights into ferrate (VI) activation by Mn-modified sludge biochar for sulfamethoxazole degradation: Dominance of hydroxyl group and Mn-O bond in the non-radical pathway

Ferrate (Fe (VI)), as a versatile oxidizer, has been widely employed for water treatment. However, the rapid self-decomposition of Fe (VI) diminishes its practical application efficiency. In this study, a novel Mn-modified sludge biochar (MSBC) was synthesized for the first time to activate Fe (VI) and generate highly reactive Fe (IV)/Fe (V) for the rapid removal of sulfamethoxazole (SMX). The results showed that MSBC (0.10 g/L) effectively activated Fe (VI) (100 μM), and 87.39 % of SMX (10 μM) and 40.26 % of total organic carbon (TOC) were removed within 10 min. Notably, raising the solution pH (e.g., from 6.0 to 11.0) would result in decreasing the reactivity of Fe (VI) and a lower removal efficiency of SMX. The quenching, electron paramagnetic resonance and probe experiments suggested that •O2– and high-valent iron species (Fe (V)/Fe (IV)) were identified as the major contributions to the removal of SMX. The detailed activation sites of MSBC were –OH and Mn-O, as corroborated by density functional theory (DFT) calculation and characterization. These activation sites facilitated activation of Fe (VI) through efficient electron transfer. The Fukui index indicated that the N, S, and O atom of SMX were the primary attacked sites. Subsequently, five potential degradation pathways were proposed, with the cleavage of the S-N bond being the predominant one. The toxicity of these products was examined using ECOSAR program, revealing that main products showed low toxicity or non-toxicity. The Cl-, SO42-, and NO3– had negligible effect on SMX degradation, although excessive concentrations of HCO3– and humic acid (HA) showed slightly inhibition. Additionally, the Fe (VI)/MSBC system also effectively removed 87.34 % of sulfadiazine (SDZ) and 93.91 % of sulfamethoxypyridazine (SMP). Overall, this study offered a practical and cost-effective approach for the activation of Fe (VI) and provided new insights to the degradation mechanism.

Bioinspired axial S-coordinated single-atom cobalt catalyst to efficient activate peroxymonosulfate for selective high-valent Co-Oxo species generation

The efficient activation and selective high-valent metal-oxo (HVMO) species generation remain challenging for peroxymonosulfate (PMS)-based advanced oxidation processes (PMS-AOPs) in water purification. The underlying mechanism of the activation pathway is ambiguous, leading to a massive dilemma in the control and regulation of HVMO species generation. Herein, bioinspired by the bio-oxidase structure of cytochrome P450, the axial coordination strategy was adopted to tailor a single-atom cobalt catalyst (CoN4S-CB) with an axial S coordination. CoN4S-CB high-selectively generated high-valent Co-Oxo species (Co(IV)=O) via PMS activation. Co(IV)=O demonstrated an ingenious oxygen atom transfer (OAT) reaction to achieve the efficient degradation of sulfamethoxazole (SMX), and this allowed robust operation in various complex environments. The axial S coordination modulated the 3d orbital electron distribution of the Co atom. Density functional theory (DFT) calculation revealed that the axial S coordination decreased the energy barrier for PMS desorption and lowered the free energy change (ΔG) for Co(IV)=O generation. CoN4S-PMS* had a narrow d-band close to the Fermi level, which enhanced charge transfer to accelerate the cleavage of O-O and O-H bonds in PMS. This work provides a broader perspective on the activator design with natural enzyme structure-like active sites to efficient activate PMS for selective HVMO species generation.

Radiation-induced preparation of nanoscale CoO@graphene oxide for activating peroxymonosulfate to degrade emerging organic pollutants

In this study, ionizing radiation was used to induce the in-situ formation of highly dispersed nanosized cobalt oxide on the surface of graphene oxide (R-Co-GO), which was highly effective for activating PMS to degrade sulfamethoxazole (SMX). R-Co-GO had the highest catalytic activity when 150 μL cobalt chloride hexahydrate solution was used in the precursor, and the pseudo first-order kinetic constant of SMX degradation was 0.07 min−1 with high mineralization efficiency (63.1 %) and high PMS utilization efficiency. The sulfate radicals and high-valent cobalt oxo were mainly responsible for SMX degradation. Mechanism analysis showed that cobalt active site dominated in PMS activation, which was responsible for the formation of sulfate radicals and high-valent cobalt oxo; while the carbon framework contributed to the formation of singlet oxygen. The R-Co-GO-150 had good catalytic activity and stability in five cycling experiments, in which SMX was completely degraded and the concentration of dissolved Co was below 0.1 mg/L. In addition, the R-Co-GO-150/PMS system could also degrade phenol, bisphenol A, atrazine and nitrobenzene effectively, confirming its wide applicability. This study provided a facile method to uniformly disperse the metal oxides on the surface of carbon materials, and an effective system for the removal of emerging organic pollutants from the actual wastewater.

Comparative study on the activation of peroxymonosulfate and peroxydisulfate by Ar plasma-etching CNTs for sulfamethoxazole degradation: Efficiency and mechanisms.

Sulfamethoxazole (SMX), a widely utilized antibiotic, was continually detected in the environment, causing serious risks to aquatic ecology and water security. In this study, carbon nanotubes (CNTs) with abundant defects were developed by argon plasma-etching technology to enhance the activation of persulfate (PS, including peroxymonosulfate (PMS) and peroxydisulfate (PDS) ) for SMX degradation while reducing environmental toxicity. Obviously, the increase of ID/IG value from 0.980 to 1.333 indicated that Ar plasma-etching successfully introduced rich defects into CNTs. Of note, Ar-90-CNT, whose Ar plasma-etching time was 90 min with optimum catalytic performance, exhibited a significant discrepancy between PMS activation and PDS activation. Interestingly, though the Ar-90-CNT/PDS system (kobs = 0.0332 min-1) was more efficient in SMX elimination than the Ar-90-CNT/PMS system (kobs = 0.0190 min-1), Ar plasma-etching treatment had no discernible enhancement in the catalytic efficiency of MWCNT for PDS activation. Then the discrepancy on activation mechanism between PMS and PDS was methodically investigated through quenching experiments, electron spin resonance (ESR), chemical probes, electrochemical measurements and theoretical calculations, and the findings unraveled that the created vacancy defects were the ruling active sites for the production of dominated singlet oxygen (1O2) in the Ar-90-CNT/PMS system to degrade SMX, while the electron transfer pathway (ETP), originated from PDS activation by the inherent edge defects, was the central pathway for SMX removal in the Ar-90-CNT/PDS system. Based on the toxicity test of Microcystis aeruginosa, the Ar-90-CNT/PDS system was more effective in alleviating environmental toxicity during SMX degradation. These findings not only provide insights into the discrepancy between PMS activation and PDS activation via carbon-based materials with controlled defects regulated by the plasma-etching strategy, but also efficiently degrade sulfonamide antibiotics and reduce the toxicity of their products.

Varying removal of emerging organic contaminants in drinking water treatment residue-based biofilter systems: Influence of hydraulic loading rates on microbiology

Drinking water treatment residue (DWTR)-based biofilter is an environment-friendly and cost-effective technology for eliminating nutrients and emerging organic contaminants (EOCs) from natural water. This study explored the removal efficiencies of five trace-level EOCs and the associated microbial response of biofilm in two identical DWTR-based biofilters under varying hydraulic loading rate (HLR) conditions over six months of operation. The results showed that the most recalcitrant EOC (carbamazepine) was mainly removed by DWTR adsorption (7.8–11.0 ng g−1), while the response of the biofilm community to HLR significantly affected the degradation of 17α-ethinylestradiol, sulfamethoxazole, roxithromycin, and sulfathiazole (P < 0.001). A higher HLR significantly stimulated the production of extracellular polymeric substance and increased the stochasticity and diversity of community assembly, improving denitrification and the removal efficiency of DWTR-based biofilm for biodegradable roxithromycin (80 %) and sulfamethoxazole (76 %). In contrast, lower HLR led to carbon limitation and exerted substrate selection pressures, resulting in more deterministic and stable community assembly, with keystone species such as Bacillus enriched in EOC degradation-related functional genes. Moreover, co-occurrence network analysis revealed a simpler but more intensive interaction network among EOC degraders under the lower HLR condition. This interaction network facilitated the co-metabolism of influent organic carbon and the removal of more recalcitrant contaminants, 17α-ethinylestradiol (48 %) and sulfathiazole (37 %). This study offered a novel insight into biofilter management from a hybrid perspective of environmental microbiology and engineering science, highlighting the dynamic adaptation of microbes to specific EOC degradation under varying HLR conditions.

MXene-regulated non-radical dominated degradation of binary sulfadiazine and sulfamethoxazole in semi-coke supported MXene/persulfate system

Sulfadiazine (SDZ) and sulfamethoxazole (SMX) are typical sulfonamide drugs that may pose potential risks to aquatic environment and organisms. Here, a small amount of MXene was introduced into an industrial waste semi-coke (SC) to prepare SC supported MXene (SC-MXene) heterogeneous catalyst for activating persulfate (PS) to degrade SDZ and SMX simultaneously. At SC to MXene ratio of 20:1, pH=7.0, T=30 °C, 0.20g/L SC-MXene and 0.50g/L PS, the developed SC-MXene/PS system had the degradation efficiency of 99.8% for SDZ and 99.9% for SMX within 120min. Furthermore, this system was able to efficiently degrade the target pollutants over a wide pH range of 3-9, with the degradation process being significantly promoted in the presence of Cl- and HCO3-. Compared with SC/PS system dominated by free radicals, SC-MXene/PS system was mainly controlled by non-radical 1O2 and electron transfer process, and thus was less susceptible to external factors and more conducive to the treatment of multiple antibiotics in real wastewaters. Compared to other relevant studies on MXene, this study demonstrates the unique role of MXene as an effective modifier for carbon-based catalysts, achieving a low-cost transformation of PS activation from free radical to non-radical pathways, and offering a promising option for the design of high-performance carbon-based catalysts in a non-radical dominated role via MXene regulation.

LaCoO3@Fe3O4 as peroxymonosulfate activator derived from spent lithium battery cathode materials for degradation of sulfamethoxazole in water

LaCoO3@Fe3O4 as peroxymonosulfate activator derived from spent lithium battery cathode materials for degradation of sulfamethoxazole in water

Photocatalytic activity of barium titanate composites with zinc oxide doped with lanthanide ions for sulfamethoxazole degradation

This comprehensive study delves into the structural and optical characteristics of barium titanate (BT) and zinc oxide (ZnO) heterostructures doped with europium (Eu), erbium (Er), and ytterbium (Yb), alongside their application in the photodegradation of sulfamethoxazole antibiotic (SMX). The heterostructures, prepared via a hydrothermal process, exhibit a heterogeneous connection between doped ZnO nanoparticles and the BT dielectric material with crystalline nature and chemical composition. Moreover, a significant reduction in the bandgap of the doped BT@ZnO:Ln heterostructures compared to undoped counterparts, indicating successful dopant incorporation and the creation of new sub-bands within the bandgap. A minimal adsorption interaction between SMX and the nanomaterials was observed. While BT alone exhibited limited photocatalytic activity, doping with ZnO significantly enhanced performance. Notably, the BT@ZnO:Yb heterostructure exhibited exceptional SMX degradation (99%) within 60 minutes. Incorporation of rare-earth ions (Eu, Er, Yb) not only improved photocatalytic activity but also acted as electron scavengers, mitigating electron-hole recombination. Furthermore, the investigation into the reuse of BT@ZnO:Yb 5%mol showed sustained high efficiency over three cycles. Mechanistic insights into SMX degradation pathways highlight the predominant role of hydroxyl radicals and electron-hole processes. Overall, these findings contribute significantly to the advancement of photocatalytic materials based on composites doped with lanthanide ions for applications in environmental wastewater treatment.

Sulfur doping-induced morphological and electronic structure modification of polyoxometalate FeWO4 for enhanced removal of organic pollutants from water

Wolframite (FeWO4), a typical polyoxometalate, serves as an auspicious candidate for heterogeneous catalysts, courtesy of its high chemical stability and electronic properties. However, the electron-deficient surface-active Fe species in FeWO4 are insufficient to cleave H2O2 via Fe redox-mediated Fenton-like catalytic reaction. Herein, we doped Sulfur (S) atom into FeWO4 catalysts to refine the electronic structure of FeWO4 for H2O2 activation and sulfamethoxazole (SMX) degradation. Furthermore, spin-state reconstruction on S-doped FeWO4 was found to effectively refine the electronic structure of Fe in the d orbital, thereby enhancing H2O2 activation. S doping also accelerated electron transfer during the conversion of sulfur species, promoting the cycling of Fe(III) to Fe(II). Consequently, S-doped FeWO4 bolstered the Fenton-like reaction by nearly two orders of magnitude compared to FeWO4. Significantly, the developed S-doped FeWO4 exhibited a remarkable removal efficiency of approximately 100% for SMX within 40 min in real water samples. This underscores its extensive pH adaptability, robust catalytic stability, and leaching resistance. The matrix effects of water constituents on the performance of S-doped FeWO4 were also investigated, and the results showed that a certain amount of Cl−, SO42−, NO3−, HCO3− and PO43− exhibited negligible effects on the degradation of SMX. Theoretical calculations corroborate that the distinctive spin-state reconstruction of Fe center in S-doped FeWO4 is advantageous for H2O2 decomposition. This discovery offers novel mechanistic insight into the enhanced catalytic activity of S doping in Fenton-like reactions and paves the way for expanding the application of FeWO4 in wastewater treatment.

Modulating electronic structure of active sites on iron-based nanoparticles enhances peroxymonosulfate activation

Herein, iron-based nanoparticle catalysts with heteroatoms anchored on nitrogen-doped carbon layers were constructed and applied to peroxymonosulfate (PMS) activation for antibiotic degradation. Results showed that S doping was beneficial to PMS activation, while P doping reduced the activation efficiency. The S-doped catalysts achieved 100% removal of sulfamethoxazole (SMX) within 15 min with a normalized rate constant of 130.4 min−1 M−1. Electron paramagnetic resonance and scavenging tests proved that high-valent iron-oxo species (HV-FeO) and singlet oxygen (1O2) mediated non-radical oxidation dominated the SMX degradation. Theoretical calculations and experiments elucidated that the electron-rich S atom donated electrons during PMS activation, which changed the valence state of Fe and enhanced the adsorption energy to PMS (Eads = −11.219 eV), resulting in excellent catalytic activity. This work elucidated the effects of heteroatoms on the electronic structure of active site in nanoparticles and provided guidance for the development of advanced catalysts for PMS activation.

Construction of BiOCl/bismuth-based halide perovskite heterojunctions derived from the metal-organic framework CAU-17 for effective photocatalytic degradation

The designed synthesis of an S-scheme heterojunction has possessed a great potential for improving photocatalytic wastewater treatment by demonstrating increased the photoredox capacity and improved the charge separation efficiency. Here, we introduce the fabrication of a heterojunction-based photocatalyst comprising bismuth oxychloride (BiOCl) and bismuth-based halide perovskite (BHP) nanosheets, derived from metal-organic frameworks (MOFs). Our composite photocatalyst is synthesized through a one-pot solvothermal strategy, where a halogenation process is applied to a bismuth-based metal-organic framework (CAU-17) as the precursor for bismuth sourcing. As a result, the rod-like structure of CAU-17 transforms into well-defined plate and nanosheet architectures after 4 and 8 h of solvothermal treatment, respectively. The modulation of the solvothermal reaction time facilitates the establishment of an S-scheme heterojunction, resulting in an increase in the photocatalytic degradation efficiency of rhodamine B (RhB) and sulfamethoxazole (SMX). The optimized BiOCl/BHP composite exhibits superior RhB and SMX degradation rates, achieving 99.8% degradation of RhB in 60 min and 75.1% degradation of SMX in 300 min. Also, the optimized BiOCl/BHP composite (CAU-17-st-8h sample) exhibited the highest rate constant (k = 3.48 × 10−3 min−1), nearly 6 times higher than that of the bare BHP in the photocatalytic degradation process of SMX. The enhanced photocatalytic efficiency can be endorsed to various factors: (i) the in-situ formation of two-components BiOCl/BHP photocatalyst, derived from CAU-17, effectively suppresses the aggregation of pristine BHP and BiOCl particles; (ii) the S-scheme heterostructure establishes a closely-knit interfacial connection, thereby facilitating efficient pathways for charge separation/transfer; and (iii) the BiOCl/BHP heterostructure enhances its capacity to absorb visible light. Our investigation establishes an effective strategy for constructing heterostructured photocatalysts, offering significant potential for application in photocatalytic wastewater treatment.

Doped Cu0 and sulfidation induced transition from R-O• to •OH in peracetic acid activation by sulfidated nano zero-valent iron-copper

Peracetic acid (PAA) has emerged as a new effective oxidant for various contaminants degradation through advanced oxidation process (AOP). In this study, sulfidated nano zero-valent iron-copper (S-nZVIC) with low Cu doping and sulfidation was synthesized for PAA activation, resulting in more efficient degradation of sulfamethoxazole (SMX, 20 μM) and other contaminants using a low dose of catalyst (0.05 g/L) and oxidant (100 μM). The characterization results suggested that S-nZVIC presented a more uniform size and distribution with fewer metal oxides, as the agglomeration and oxidation were inhibited. More significantly, doped Cu0 and sulfidation significantly enhanced the generation and contribution of •OH but decreased that of R-O• in S-nZVIC/PAA/SMX system compared with that of nZVIC and S-nZVI, accounting for the relatively high degradation efficiency of 97.7% in S-nZVIC/PAA/SMX system compared with 85.7% and 78.9% in nZVIC/PAA/SMX and S-nZVI/PAA/SMX system, respectively. The mechanisms underlying these changes were that (i) doped Cu° could promote the regeneration of Fe(Ⅱ) for strengthened PAA activation through mediating Fe(Ⅱ)/Fe(Ⅲ) cycle by Cu(Ⅰ)/Cu(Ⅱ) cycle; (ii) S species might consume part of R-O•, resulting in a decreased contribution of R-O• in SMX degradation; (iii) sulfidation increased the electrical conductivity, thus facilitating the electron transfer from S-nZVIC to PAA. Consequently, the dominant reactive oxygen species transited from R-O• to •OH to degrade SMX more efficiently. The degradation pathways, intermediate products and toxicity were further analyzed through density functional theory (DFT) calculations, liquid chromatography-mass spectrometry (LC-MS) and T.E.S.T software analysis, which proved the environmental friendliness of this process. In addition, S-nZVIC exhibited high stability, recyclability and degradation efficiency over a wide pH range (3.0∼9.0). This work provides a new insight into the rational design and modification of nano zero-valent metals for efficient wastewater treatment through adjusting the dominant reactive oxygen species (ROS) into the more active free radicals.

Periodate activation by MnFe2O4 spinel for sulfamethoxazole degradation: Iodate radical dominance, degradation pathway, DFT calculation and toxicity assessment

This study synthesized spinel MnFe2O4 at different temperatures, which was applied to activate periodate (PI) for sulfamethoxazole (SMX) degradation. It was found that the 500-MFO (MnFe2O4 calcined at 500 ℃) demonstrated superior activity in PI activation, with notable sustainability but strong substrate selectivity. Furthermore, a comprehensive analysis, including quenching experiment, electron paramagnetic resonance (EPR) technique, X-ray photoelectron spectroscopy (XPS) analysis, metal ions leaching detection, homogeneous PI activation, and methyl phenyl sulfoxide (PMSO) probe test, revealed that homo- and heterogeneous pathways as well as free and non-free radical routes coexisted in the 500-MFO/PI system. Multiple active species, including iodate radical (IO3•), hydroxyl radical (•OH), superoxide radical (O2•-), singlet oxygen (1O2), and Mn(IV) were identified, with IO3• from heterogeneous activation being the primary species. When PMSO and SMX coexisted, PMSO could react with Mn(IV), promoting the regeneration of Mn reaction sites and the production of IO3•, thereby being beneficial for the degradation of SMX. The degradation pathways of SMX were elucidated through high-performance liquid chromatography-mass spectrometry (HPLC-MS) and density functional theory (DFT) calculation. The acute and chronic toxicity of thirteen by-products to aquatic organisms were predicted using the Ecological Structure Activity Relationships (ECOSAR) software, with the corresponding results revealing that although the toxicity of intermediates fluctuated, the final products were environmentally benign. Therefore, this investigation provides a viable method for SMX degradation in wastewater treatment.

Effective Activation of Peroxymonosulfate by Oxygen Vacancy Induced Musa Basjoo Biochar to Degrade Sulfamethoxazole: Efficiency and Mechanism.

Biochar materials have garnered attention as potential catalysts for peroxymonosulfate (PMS) activation due to their cost-effectiveness, notable specific surface area, and advantageous structural properties. In this study, a suite of plantain-derived biochar (MBB-400, MBB-600, and MBB-800), possessing a well-defined pore structure and a substantial number of uniformly distributed active sites (oxygen vacancy, OVs), was synthesized through a facile calcination process at varying temperatures (400, 600, and 800 °C). These materials were designed for the activation of PMS in the degradation of sulfamethoxazole (SMX). Experimental investigations revealed that OVs not only functioned as enriched sites for pollutants, enhancing the opportunities for free radicals (•OH/SO4•-) and surface-bound radicals (SBRs) to attack pollutants, but also served as channels for intramolecular charge transfer leaps. This role contributed to a reduction in interfacial charge transfer resistance, expediting electron transfer rates with PMS, thereby accelerating the decomposition of pollutants. Capitalizing on these merits, the MBB-800/PMS system displayed a 61-fold enhancement in the conversion rate for SMX degradation compared to inactivated MBB/PMS system. Furthermore, the MBB-800 exhibited less cytotoxicity towards rat pheochromocytoma (PC12) cells. Hence, the straightforward calcination synthesis of MBB-800 emerges as a promising biochar catalyst with vast potential for sustainable and efficient wastewater treatment and environmental remediation.

Sources of the active substances in microwave catalytic redox processes induced by iron-based carbon materials: The key role of B doping

Organic and heavy metal water pollutants is an urgent environmental problem to be solved. Herein, a B-doped iron-based carbon material (FC-B) was synthesized and used in a microwave field for the degradation of sulfamethoxazole (SMX) and the reduction of Cr(VI). Under a low power of microwave irradiation (240 W), FC-B rapidly degraded SMX (99.8 %, 12 min) and reduced Cr(VI) (100.0 %, 14 min) without adding any oxidizing and reducing agents. SEM, XRD, XPS, and FTIR verified the successful synthesis of FC-B. And the “temperature visualization test” verified the existence of “hot spots”. The presence of O2− in the MW/FC-B system but not in the MW/FC system was verified by quenching experiments, electron paramagnetic resonance (EPR) experiments and nitro blue tetrazolium chloride (NBT) quantitative experiments, and then the conversion of microwave-generated electrons (e−) to O2− was elaborated using N2 blowing experiments, temperature-programmed desorption of O2 (O2-TPD), density functional theory (DFT) calculations and electrochemical tests. Subsequently, cycling experiments showed that FC-B has good reusability. Finally, the practical application of the MW/FC-B system was verified with antibiotic-containing farm wastewater. This study not only proposed a new technology for water pollution treatment, but also provided a pioneering explanation of the production of oxidizing substances in microwave-induced catalytic reactions.