Mineralization Of Sulfamethoxazole Research Articles

Stable isotopes and nanoSIMS single-cell imaging reveals soil plastisphere colonizers able to assimilate sulfamethoxazole

The presence and accumulation of both, plastics and antibiotics in soils may lead to the colonization, selection, and propagation of soil bacteria with certain metabolic traits, e.g., antibiotic resistance, in the plastisphere. However, the impact of plastic-antibiotic tandem on the soil ecosystem functioning, particularly on microbial function and metabolism remains currently unexplored. Herein, we investigated the competence of soil bacteria to colonize plastics and degrade 13C-labeled sulfamethoxazole (SMX). Using single-cell imaging, isotope tracers, soil respiration and SMX mineralization bulk measurements we show that microbial colonization of polyethylene (PE) and polystyrene (PS) surfaces takes place within the first 30 days of incubation. Morphologically diverse microorganisms were colonizing both plastic types, with a slight preference for PE substrate. CARD-FISH bacterial cell counts on PE and PS surfaces formed under SMX amendment ranged from 5.36 × 103 to 2.06 × 104, and 2.06 × 103 to 3.43 × 103 hybridized cells mm−2, respectively. Nano-scale Secondary Ion Mass Spectrometry measurements show that 13C enrichment was highest at 130 days with values up to 1.29 atom%, similar to those of the 13CO2 pool (up to 1.26 atom%, or 22.55 ‰). Independent Mann-Whitney U test showed a significant difference between the control plastisphere samples incubated without SMX and those in 13C-SMX incubations (P < 0.001). Our results provide direct evidence demonstrating, at single-cell level, the capacity of bacterial colonizers of plastics to assimilate 13C-SMX from contaminated soils. These findings expand our knowledge on the role of soil-seeded plastisphere microbiota in the ecological functioning of soils impacted by anthropogenic stressors.

Interaction patterns and keystone taxa of bacterial and eukaryotic communities during sulfamethoxazole mineralization in lake sediment

Sulfamethoxazole (SMX) is a common antibiotic pollutant in aquatic environments, which is highly persistent under various conditions and significantly contributes to the spread of antibiotic resistance. Biodegradation is the major pathway to eliminate antibiotics in the natural environment. The roles of bacteria and eukaryotes in the biodegradation of antibiotics have received considerable attention; however, their successions and co-occurrence patterns during the biodegradation of antibiotics remain unexplored. In this study, 13C-labled SMX was amended to sediment samples from Zhushan Bay (ZS), West Shore (WS), and Gonghu Bay (GH) in Taihu Lake to explore the interplay of bacterial and eukaryotic communities during a 30-day incubation period. The cumulative SMX mineralization on day 30 ranged from 5.2 % to 19.3 %, which was the highest in WS and the lowest in GH. The bacterial community showed larger within-group interactions than between-group interactions, and the positive interactions decreased during incubation. However, the eukaryotic community displayed larger between-group interactions than within-group interactions, and the positive interactions increased during incubation. The proportion of negative interactions between bacteria and eukaryotes increased during incubation. Fifty genera (including 46 bacterial and 4 eukaryotic genera) were identified as the keystone taxa due to their dominance in the co-occurrence network and tolerance to SMX. The cumulative relative abundance of these keystone taxa significantly increased during incubation and was consistent with the SMX mineralization rate. These taxa closely cooperated and played vital roles in co-occurrence networks and microbial community interactions, signifying their crucial role in SMX mineralization. These findings broadened our understanding of the complex interactions of microorganisms under SMX exposure and their potential functions during SMX mineralization, providing valuable insights for in situ bioremediation.

TiO2/Zeolite Composites for SMX Degradation under UV Irradiation

Sulfamethoxazole (SMX) is a common antibiotic that is considered an emerging pollutant of water bodies, as it is toxic for various aquatic species. TiO2-based photocatalysis is a promising method for SMX degradation in water. In this work, TiO2/zeolite (Z-45 loaded with TiO2 labeled as TZ and ZSM-5 loaded with TiO2 labeled as TZSM) composites were prepared by mechanical mixing and liquid impregnation methods, and the photocatalytic performance of these composites (200 mg·L−1) was investigated toward the degradation of SMX (30 mg·L−1) in water under UV light (365 nm). The pseudo-first-order reaction rate constant of the TZSM1450 composite was 0.501 min−1, which was 2.08 times higher than that of TiO2 (k = 0.241 min−1). Complete SMX degradation was observed in 10 min using the UV/TZSM1450 system. The mineralization ability in terms of total organic carbon (TOC) removal was also assessed for all of the prepared composites. The results showed that 65% and 67% of SMX could be mineralized within 120 min of photocatalytic reaction by TZSM2600 and TZSM1450, respectively. The presence of Cl− and CO32− anions inhibited the degradation of SMX, while the presence of NO3− had almost no effect on the degradation efficiency of the UV/TZSM1450 system. The electrical energy per order estimated for the prepared composites was in the range of 68.53–946.48 kWh m−3 order−1. The results obtained revealed that the TZSM1450 composite shows promising potential as a photocatalyst for both the degradation and mineralization of SMX.

Synchronously improved permeability, selectivity and fouling resistance of Fe-N-C functionalized ceramic catalytic membrane for effective water treatment: The critical role of Fe

Constructing catalytic membrane simultaneously displaying high permeability, selectivity and antifouling performance in water treatment remains challenging. Herein, the surface and pore channels of the ceramic membrane were co-functionalized with nitrogen doped carbon supported Fe catalyst (CN-F), and the Fe content was varied to investigate its effect on performance of CN-F coupled with peroxymonosulfate (PMS) activation (CN-F/PMS) for water treatment. Results confirmed the introduced Fe (in Fe-N coordination form) greatly enhanced the permeability, selectivity and fouling resistance of CN-F. Optimal CN-F3/PMS achieved 96.5% removal and 52.1% mineralization of sulfamethoxazole in short retention duration (2.7 min), whose performance was 5.4 and 6.7 times higher than that of nitrogen doped carbon functionalized ceramic catalytic membrane (CN/PMS) and CN-F3 filtration alone, respectively. CN-F3/PMS also efficiently inhibited fouling on both surface and pores with 2.8 and 2.4 times lower flux loss than that of CN/PMS and CN-F3 filtration alone, respectively. Moreover, CN-F3/PMS displayed superior performance in long-term treatment of real coking wastewater. The outstanding performance of CN-F was mainly attributed to the dual role of supported Fe, which served as hydrophilic site for enhanced water permeation and major active site for PMS adsorption and reduction into reactive species (mainly high-valent Fe(IV)=O species) towards pollutant elimination.

Iron and nitrogen modified sludge biochar efficiently activated persulfate for mineralization of sulfamethoxazole in groundwater

In this work, iron-nitrogen co-doped sludge biochar (Fe@N-SBC) was successfully prepared by a facile synthetic method using sludge as a precursor. We investigated the degradation effect of Fe@N-SBC activated peroxodisulfate (PDS) on sulfamethoxazole (SMX), a common antibiotic pollutant in groundwater, and explored its reaction mechanism. The removal of SMX in the Fe@N-SBC /PDS system reached more than 99%, and it could still reach 97.8% in actual groundwater with complex composition. Under the condition of sufficient dosage, the final mineralization of SMX can reach more than 95%, which means that there is no risk of secondary pollution of intermediate products to the environment. The main mechanism for the degradation of SMX by Fe@N-SBC/PDS system is the electron transfer mechanism mediated by the substable [Fe@N-SBC-PDS* ] complex formed on the surface of Fe@N-SBC, followed by the non-radical reaction mechanism dominated by singlet oxygen, and thus it has a wide pH range and strong resistance to ionic interference. The addition of N can significantly reduce the leaching of metal ions in the material, and the leaching amount of Fe in Fe@N-SBC is only 0.1 μg/g, while other toxic and harmful heavy metals are hardly leached. Overall, Fe@N-SBC is an environmentally friendly catalyst with simple preparation, high catalytic activity, wide applicable pH range, strong resistance to ionic interference, and selectivity for electron-rich organics, which has good application prospects in practical groundwater treatment.

Catalytic wet air oxidation of sulfamethoxazole and tetracycline using platinum-based catalysts at eco-operating conditions

Conventional wastewater treatment plants (WWTP) are unsuitable for emerging contaminants' elimination. Most of these pollutants persist after the treatment and threaten the receiving environment. Catalytic wet air oxidation (CWAO) is one of the promising solutions to treat these concentrated active molecules. This study reports the catalytic degradation tests on sulfamethoxazole (SM) and tetracycline (TET) using platinum (Pt) supported on cerium oxide (Ce) and mixed cerium and zirconium oxides (CeZr). Pt/CeZr catalyst showed 98 % TET elimination at 50 °C under atmospheric pressure (Patm). Furthermore, the test at room conditions reached 92 % removal. Pt/Ce test enabled 77 % SM elimination and reached 45 % SM mineralization. Toxicity assessment confirmed the environmental legibility of the treated solution using CWAO. The outcomes of this study showed an eco-energetic, eco-friendly, and efficient way to treat wastewater loaded with pharmaceutical pollutants.

Face-to-face interfacial assembly of a hybrid NiAl-LDH@BiOIO3 photocatalyst for the effective solar-induced abatement of antibiotic and dye pollutants: Insights into surface engineering and S-scheme charge transfer

The development of hybrid catalysts with 2D/2D interfacial contact and step-scheme (S-scheme) charge transfer is crucial for photocatalysis because these catalysts potentially offer more efficient photoexcited charge separation and separated charge carriers with a stronger redox capability. In this study, we strategically developed a novel hybrid NiAl layered double hydroxide (LDH)@BiOIO3 (BOI) photocatalyst with effective S-scheme charge transfer for the efficient solar-induced abatement of aqueous antibiotic and dye pollutants. The in-situ growth of LDH sheets on BOI sheets yielded a hybrid 2D/2D LDH@BOI photocatalyst with favorable face-to-face interfacial contact, which provided a broader platform for photoinduced charge migration and minimizes charge recombination. Furthermore, the S-scheme charge transfer mechanism within the hybrid photocatalyst effectively promoted the separation of the photoinduced charge carriers and preserved their strong redox capability. These beneficial features, in combination with the large specific surface area and enhanced light-harvesting capability, were responsible for the exceptional photocatalytic performance of the optimized hybrid LDH@BOI photocatalyst in terms of the degradation and mineralization of sulfamethoxazole and Congo red dye. Notably, the proposed hybrid photocatalyst outperformed BOI and LDH individually and previously reported state-of-the-art photocatalysts while maintaining its stability over consecutive test cycles, highlighting it as a promising candidate for photocatalytic applications.

Deep degradation of sulfamethoxazole by the Fe-Co/γ-Al2O3-catalysed photo-Fenton system

ABSTRACT The heterogeneous photo-Fenton system using Fe-Co/γ-Al2O3 as a catalyst was applied in the study of sulfamethoxazole(SMX) degradation. The morphology, structure, elemental composition and metal valence distribution of Fe-Co/γ-Al2O3 were found to be relatively stable before and after the reaction. The highest SMX degradation efficiency and mineralization (The ratio of organic matter being oxidized to carbon dioxide and water) were obtained under the conditions of 15% Fe-Co loading rate, 1:1 mass ratio of Fe and Co, 1 g/L catalyst dosage, 1.5 mL 30% H2O2 dosage, 18 W UV lamp power and 60 min reaction time, which were 98% and 66%, respectively. Radical quenching experiments and electronic paramagnetic resonance (EPR) characterization revealed that ·OH played an important role in the degradation and mineralization SMX in the Fe-Co/γ-Al2O3 heterogeneous photo-Fenton system. Combined with the analysis of N, S and intermediate products, there may be three degradation pathways of SMX in the heterogeneous photo-Fenton system. This work provides a technical reference for realizing the efficient degradation and mineralization of SMX in a heterogeneous photo-Fenton reaction system.

Reduced graphene oxide supported CoFe2O4 composites with enhanced peroxymonosulfate activation for the removal of sulfamethoxazole: Collaboration of radical and non-radical pathways

In this work, an environmentally friendly reduced graphene oxidized supported cobalt ferrite (CFO/rGO) catalyst was constructed using a hydrothermal technique to heterogeneously activate peroxymonosulfate (PMS) and utilized for the degradation of sulfamethoxazole (SMX) antibiotic in aqueous solution. The results exhibited that the complete degradation of SMX was achieved in 25 min under optimal conditions ([SMX] = 8.0 mg/L, [CFO/rGO-30%] = 0.5 g/L, [PMS] = 5.0 mM, pH = 7.0) in the presence of CFO/rGO-30%/PMS with a rate constant of 0.3076 min˗1, which was roughly 6.08 times higher compared to the CoFe2O4/PMS system (0.0506 min˗1). The enhanced degradation of SMX in the CFO/rGO-30%/PMS system might be attributed to the large surface area of the CFO/rGO-30% (98.11 m2/g) catalyst compared to the pristine CoFe2O4 (24.31 m2/g), which increased the availability of active sites for PMS activation. Furthermore, the influence of pivotal reaction parameters and interfering anions on SMX mineralization was also scrutinized. The formation of free radicals (SO4•−, •OH, and 1O2) was established through quenching experiments and electron paramagnetic resonance analysis. The degradation mechanism of SMX was speculated based on the identification of degradation intermediates and X-ray photoelectron spectroscopy spectral analysis. Mechanistic investigations suggested that the transition of Co2+/Co3+ and Fe3+/Fe2+ pairs on the catalyst surface was responsible for the PMS activation, and the SMX degradation was accomplished through radical and non-radical pathways. Furthermore, CFO/rGO-30% exhibited high stability after four consecutive cycles and maintained catalytic activity. Finally, the developed CFO/rGO-30% catalyst exhibited promising potential for the purification of SMX polluted water.

Layered double hydroxide driven 1O2 non-radical or •OH radical process for the degradation, transformation and even mineralization of sulfamethoxazole via efficient peroxymonosulfate activation

As reported, PMS can be activated and decomposed into different reactive oxygen species such as 1O2, •OH and SO4•-, besides, coupling of non-radical (PMS direct oxidation) and radical (SO4•-) process could enhance the utilization efficiency of PMS. In this study, we proposed another strategy of 1O2-based non-radical and •OH-based radical process using layered double hydrotalcite (MgAl-LDH and MgAlCu-LDH) to regulate the degradation, transformation and even mineralization of sulfamethoxazole. Compared with PMS direct oxidation, SMX removal efficiency was increased from 41.8% to 71.7% by 1O2. However, there was almost no real degradation or mineralization since the ionization intermediates including C10H12N3O4S and C7H9N3O5S accumulated with reaction time according to DFT and LC-MSMS analysis. In comparison, 100% of SMX degradation was obtained via coupling 1O2 and •OH-radical process, in which the mineralization efficiency reached to 24.8%. Importantly, the above-mentioned intermediates of SMX were not detected and their accumulation were also significantly inhibited. Moreover, SMX degradation behavior and kinetics could be manipulated via direct oxidation, 1O2 and then •OH step by step, which was beneficial to enhance the PMS utilization efficiency. Finally, based on the results of zeta potential of MgAlCu-LDH, effect of solution pH on SMX degradation, the interfacial PMS activation process was responsible to regulate non-radical and radical process.

Well-defined Fe/Cu diatomic catalysts for boosted peroxymonosulfate activation to degrade organic contaminants

The Fe-N-C catalyst with a FeNx active site has gained ever-increasing attention for peroxymonosulfate (PMS) activation to degrade organic contaminants, however, the regulation of the electronic configuration of Fe centers to further enhance the catalytic ability still remains a huge challenge. Herein, a well-defined Fe/Cu diatomic catalyst (Fe/CuDA-NC) was successfully fabricated. The Fe/CuDA-NC/PMS system can almost completely degrade sulfamethoxazole (SMX) in a wide pH range (3.0–9.0). Significantly, the degradation rate constant in Fe/CuDA-NC/PMS reaction (0.4672 min−1) was twice as high as that in Fe single-atom Fenton-like system (0.2213 min−1). Theoretical simulations illustrated that electron transfer from nearby Cu atom to Fe atom effectively optimized the bonding orbital distribution in the Fe 3d orbitals and subsequently promoted the adsorption and activation of PMS. Besides, the sulfate radicals (SO4−·), hydroxyl radicals (OH), superoxide radicals (O2–), high-valent metal-oxo species, and mediate metal-peroxo intermediates, made vital contributions to the decomposition and mineralization of SMX. We further deposited the catalysts on the widely used polyvinylidene fluoride (PVDF) microfiltration membrane and demonstrated that the target contaminants were oxidized to remove over 90 % in 60 min when passing through the filter, which showed the prospect of utilizing this novel catalyst in practical applications.

Fabrication of an intimately coupled photocatalysis and biofilm system for removing sulfamethoxazole from wastewater: Effectiveness, degradation pathway and microbial community analysis

Sulfamethoxazole (SMX) is an extensively applied antibiotic frequently detected in municipal wastewater, which cannot be efficiently removed by conventional biological wastewater processes. In this work, an intimately coupled photocatalysis and biodegradation (ICPB) system consisting of Fe3+-doped graphitic carbon nitride photocatalyst and biofilm carriers was fabricated to remove SMX. The results of wastewater treatment experiments showed that 81.2 ± 2.1% of SMX was removed in the ICPB system during the 12 h, while only 23.7 ± 4.0% was removed in the biofilm system within the same time. In the ICPB system, photocatalysis played a key role in removing SMX by producing hydroxyl radicals and superoxide radicals. Besides, the synergism between photocatalysis and biodegradation enhanced the mineralization of SMX. To understand the degradation process of SMX, nine degradation products and possible degradation pathways of SMX were analyzed. The results of high throughput sequencing showed that the diversity, abundance, and structure of the biofilm microbial community remained stable in the ICPB system at the end of the experiments, which suggested that microorganisms had accommodated to the environment of the ICPB system. This study could provide insights into the application of the ICPB system in treating antibiotic-contaminated wastewater.

Mechanism and security of UV driven sodium percarbonate for sulfamethoxazole degradation using DFT and metabolomic analysis

Recently, sodium percarbonate (SPC) as a solid substitute for H2O2 has aroused extensive attention in advanced oxidation processes. In current work, the degradation kinetics and mechanisms of antibiotic sulfamethoxazole (SMX) by ultraviolet (UV) driven SPC system were explored. The removal efficiency of SMX was enhanced as the increasing dosage of SPC. Moreover, hydroxyl radical (•OH), carbonate radical (CO3•−) and superoxide radical (O2•−) were verified to be presented by scavenger experiments and •OH, CO3•− exhibited a significant role in SMX degradation. Reactions mediated by these radicals were affected by anions and natural organic matters, implying that an incomplete mineralization of SMX would be ubiquitous. The screening four intermediates and transformation patterns of SMX were verified by DFT analysis. Metabolomic analysis demonstrated that a decreasing negative effect in E. coli after 24 h exposure was induced by intermediates products. In detail, SMX interfered in some key functional metabolic pathways including carbohydrate metabolism, pentose and glucuronate metabolism, nucleotide metabolism, arginine and proline metabolism, sphingolipid metabolism, which were mitigated after UV/SPC oxidation treatment, suggesting a declining environmental risk of SMX. This work provided new insights into biological impacts of SMX and its transformation products and vital guidance for SMX pollution control using UV/SPC technology.

Pd nanoparticles decorated BiVO4 pine architectures for photocatalytic degradation of sulfamethoxazole

Sulfamethoxazole (SMX) has been extensively detected in wastewater treatment plant effluents and surface water. Because of its potential risks to ecology and health, treatment for eliminating SMX is urgently required. In this study, we report the application of Pd nanoparticles decorated on BiVO4 pine architecture for the photocatalytic degradation of SMX. The results showed that the barer BiVO4 and Pd–BiVO4 eliminated SMX under visible-light irradiation. After 210 min of irradiation, 98.8% of SMX was substantially eliminated by Pd–BiVO4, whereas bare BiVO4 can degraded approximately 36.3% of SMX. Pd–BiVO4 also exhibited a high mineralization rate (84% of total organic carbon (TOC) removal) compared to bare BiVO4 (51% of TOC removal). Through three-dimensional excitation-emission matrix fluorescence spectra, SMX with high fluorescence intensity can be degraded to non-fluorescence intermediate products, further confirming the high mineralization of SMX over Pd–BiVO4 catalyst. Well-dispersed Pd nanoparticles on the {040} facet of BiVO4 pine architecture can support the recombination of photogenerated charge carriers because of the formation of the Schottky junction at the Pd–BiVO4 interface. Besides, the active species trapping tests indicated that •O2− and h+ radicals dominate SMX photodegradation over Pd–BiVO4. The main degradation intermediates of SMX in the reaction solution was also identified through ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry analysis. This investigation can provide insight into designing metallic/semiconductor junctions for antibiotic elimination in water media.

Zeolite supported TiO2 for the degradation and mineralization of sulfamethoxazole under UV light irradiation

Zeolites have been widely regarded as promising supporting host materials for the catalyst due to their unique structure, high surface area and excellent adsorption capacity. In this work, TiO2 particles were deposited on the surface of zeolite and used as catalyst for photocatalytic degradation of sulfamethoxazole in water under UV light irradiation (365 nm). XRD, Raman spectroscopy, SEM/EDS, UV-Vis diffuse reflectance spectroscopy (DRS) and BET analysis were used to investigate the physico-chemical properties of prepared catalysts. Among prepared catalysts, TiO2/Z-500 exhibited better photocatalytic performance by achieving complete sulfamethoxazole (30 mg/L) degradation after 20 min of reaction and ~18% of TOC removal after 120 min.

Bimetallic and nitrogen co-doped biochar for peroxymonosulfate (PMS) activation to degrade emerging contaminants

In this study, the bimetallic and nitrogen co-doped biochar was prepared for peroxymonosulfate (PMS) activation to degrade emerging contaminants. Compared to single metal-doped biochar, bimetallic-doped biochar showed much higher catalytic activity. Iron and cobalt co-doped biochar (FeCo-BC) exhibited higher catalytic activity than iron and copper co-doped biochar (FeCu-BC). When FeCo-BC was used for PMS activation, sulfamethoxazole (SMX) could be completely removed within 10 min, with the degradation rate of 0.749 min−1, which was 2.3 and 69.4 times higher than that of Fe-BC (0.333 min−1) and Co-BC (0.0108 min−1), respectively, demonstraing the synergistic effect of bimetallic co-doping. Meanwhile, the SMX mineralization efficiency reached 57.1 %. In the system of FeCo-BC/PMS, multi reactive species produced, in which hydroxyl radicals, sulfate radicals and high-valent metal-oxo mainly contributed to SMX degradation. The superior catalytic activity of FeCo-BC was attributed to the configuration of FeNx-CoNx. In five consecutive experiments, FeCo-BC showed good catalytic activity and stability. This study provides a way to the rational design of high efficient and stable PMS catalyst, which could be used in Fenton-like reaction to remove the emerging organic contaminants.

Catalytic activation of persulfate by mechanically-treated natural pyrite: Revisit on the dominant role of sulfur vacancies and size effect

Mechanical treatment has been widely used to modify the surface properties of nature pyrite minerals and improve their catalytic performances; however, the mechanistic relationship still keeps unclear. In this study, we have systematically investigated the effect of milling speed treatment on the surface characteristics of commercial natural pyrite and evaluated the activation ability of persulfate (PDS) for the degradation of sulfamethoxazole (SMX). The results demonstrated that increase in the milling speed of 200–600 rpm could dramatically enhance the degradation and mineralization of SMX, while lower speed (≤200 rpm) exhibited marginal effect. The high milling speeds could reduce the content of sulfate and S(-II) in the pyrite and lead to the occurrence of sulfur vacancies (SVs) for promotional activation of PDS. Nevertheless, the SVs content was not in accordance with increased speed and size effect would mainly contribute to the efficient degradation of SMX. The milling pyrite/PDS system could efficiently treat a molasses-processed wastewater with COD removal of 770 mg/L, suggesting slow-release function of pretreated pyrite and it broaden application potential. In addition, based on the novel conclusion of the mechanism, this study provided a green, efficient and economical pyrite mechanical activation method and its application.

N and S co-doping of TiO2@C derived from in situ oxidation of Ti3C2 MXene for efficient persulfate activation and sulfamethoxazole degradation under visible light

Visible-light-driven photocatalysts with synergistic persulfate (PS) activation and photocatalysis possess enormous pollution-control potential. Herein, nitrogen and sulphur co-doped TiO2@C hybrid (N/S-TiO2@C) featuring the complementary visible-light photocatalysis and synergetic PS activation was synthesized by in situ oxidation of Ti3C2 MXene and thereafter co-doping with N and S. Both anatase and rutile phases of TiO2 were attained in N/S-TiO2@C. The decrease of TiO2 bandgap (about 1.81 eV) and the defect of carbon layer caused by the N and S co-doping in both TiO2 crystal and carbon layer enabled the synergistic enhancement of PS activation and photocatalysis. Complete degradation and 93.4% mineralization of sulfamethoxazole (SMZ, 10 mg/L) were achieved by dosing PS (2 mM) and N/S-TiO2@C (0.4 g/L) under visible light within 30 min. The degradation rate by N/S-TiO2@C through PS activation under visible light was 27.9-, 11.1-, and 2.30-fold higher than that by PS, N-TiO2@C, and S-TiO2@C alone, respectively. Reactive species SO4−,1O2, OH, and O2−, especially the former two, were determined dominating the SMZ degradation, and the degradation pathways were illustrated through intermediates identification. Moreover, N/S-TiO2@C kept excellent performance in activating PS to degrade SMZ in real water samples. These results indicate that N/S-TiO2@C is a stable and promising PS activator under visible light and has a good application potential in organic wastewater treatment.

Mineralization of sulfamethoxazole by ozone-based and Fenton/Fenton-like-based processes

Mineralization of sulfamethoxazole by ozone-based and Fenton/Fenton-like-based processes

Degradation of sulfamethoxazole (SMX) by water falling film DBD Plasma/Persulfate: Reactive species identification and their role in SMX degradation

The performance and mechanism of persulfate on improving the degradation of sulfamethoxazole (SMX) in a water falling film dielectric barrier discharge (DBD) plasma reactor have been studied. Both peroxymonosulfate (PMS) and peroxydisulfate (PDS) improved the degradation and mineralization of SMX, but PMS presented higher SMX degradation than PDS. Moreover, increases in applied voltage, solution pH and PMS/PDS concentration promoted SMX degradation. The reactive species were qualitatively and quantitatively detected by electron paramagnetic resonance (EPR) spectra and chemical probes. The results show that the activation process of PMS/PDS by discharge plasma produced reactive radicals including ·OH and SO4·-, and PMS led to higher aqueous O3 and ·OH concentrations than PDS; scavengers of ·OH, SO4·-, O2·- and 1O2 in SMX solution decreased SMX degradation, but scavengers of hydrated electrons and H· in SMX solution had little effect on SMX degradation. The detected degradation products of SMX included 5-amino-3-methylisoxazole, 4-aminobenzenesulfonic acid, nitrosobenzene and 4-nitro sulfamethoxazole, etc., and the calculation results show that most of these products had lower toxicities than SMX. Our study indicates that the combination of DBD plasma and PMS/PDS is an efficient pretreatment method for bio-treatment of refractory SMX.