Removal Rates Of Sulfamethoxazole Research Articles

Photo-assisted natural chalcopyrite activated peracetic acid for efficient micropollutant degradation

The effective activation of natural chalcopyrite (CuFeS2) on peracetic acid (PAA) to remove organic micropollutants was studied under visible light irradiation. Results showed than an effective sulfamethoxazole (SMX) degradation (95.0 %) was achieved under visible light irradiation for 30 min at pH 7.0. Quenching experiments, electron spin resonance analysis, and LC/MS spectrum demonstrated that HO• and CH3C(O)OO• were the main reactive species for SMX degradation, accounting for 43.3 % and 56.7 % of the contributions, respectively. Combined with X-ray photoelectron spectroscopy analysis, the photoelectrons generated on CuFeS2 activated by visible light enhanced the Fe3+/Fe2+ and Cu2+/Cu+ cycles on the surface, thereby activating PAA to generate HO•/CH3C(O)OO•. The removal rate of SMX decreased with the increase in wavelengths, due to the formation of low energy photons at longer wavelengths. Besides, the optimal pH for degradation of SMX by CuFeS2/PAA/Vis-LED process was neutral, which was attributed to the increasing easily activated anionic form of PAA during the increase in pH and the depletion of Fe species at alkaline conditions. Cl−, HCO3−, and HA slightly inhibited SMX degradation because of reactive species being quenched and/or shielding effect. Furthermore, the degradation efficiency of different pollutants by CuFeS2/PAA/Vis-LED was also measured, and the removal efficiency was different owing to the selectivity of CH3C(O)OO•. Finally, the process exhibited good applicability in real waters. Overall, this study provides new insight into visible light-catalyzed activation of PAA and suggests on further exploration of the intrinsic activation mechanism of PAA.

Efficient removal of sulfamethoxazole by activated peroxodisulphates using Fe/N co-doped biochar: The minimal role of high-valent iron species

The harmful effects of the widespread presence of sulfamethoxazole (SMX) in water on ecosystems have become an increasingly pressing concern, necessitating the urgent development of an effective decontamination strategy. In this work, iron and nitrogen co-doped biochar (Fe-N-BC) samples were synthesized using peanut shells as a precursor to activate peroxydisulfate for SMX degradation. The most effective Fe-N-BC had a 12 times higher SMX removal rate of 97.00% within 90 min compared to the pristine biochar. The excellent catalytic performance was achieved by the synergistic effect of the Fe and N active sites, and the system contained not only typical free radicals (SO4− and OH) but also high-valent iron species (Fe(IV)). Further quantitative experiments with active species revealed that the free radical reaction pathway played a predominant role, while the relative contribution of Fe(IV) was only 8.01%. Furthermore, the degradation pathways of SMX in the system were proposed, and toxicity assessment revealed that all intermediate products exhibited lower toxicity levels than SMX. This study clarifies the structure–activity relationships of Fe-N-BC for PDS activation and offers an innovative strategy for the treatment and utilization of agricultural waste biomass as the catalyst.

Enzyme-induced reactive oxygen species trigger oxidative degradation of sulfamethoxazole within a methanotrophic biofilm

Although microorganisms carrying copper-containing membrane-bound monooxygenase (CuMMOs), such as particulate methane monooxygenase (pMMO) and ammonia monooxygenase (AMO), have been extensively documented for their capability to degrade organic micropollutants (OMPs), the underlying reactive mechanism remains elusive. In this study, we for the first time demonstrate biogenic reactive oxygen species (ROS) play important roles in the degradation of sulfamethoxazole (SMX), a representative OMP, within a methane-fed biofilm. Highly-efficient and consistent SMX biodegradation was achieved in a CH4-based membrane biofilm reactor (MBfR), manifesting a remarkable SMX removal rate of 1210.6 ± 39.0 μg·L−1·d−1. Enzyme inhibition and ROS clearance experiments confirmed the significant contribution of ROS, which were generated through the catalytic reaction of pMMO and AMO enzymes, in facilitating SMX degradation. Through a combination of density functional theory (DFT) calculations, electron paramagnetic resonance (EPR) analysis, and transformation product detection, we elucidated that the ROS primarily targeted the aniline group in the SMX molecule, inducing the formation of aromatic radicals and its progressive mineralization. In contrast, the isoxazole-ring was not susceptible to electrophilic ROS attacks, leading to accumulation of 3-amino-5-methylisoxazole (3A5MI). Furthermore, microbiological analysis suggested Methylosarcina (a methanotroph) and Candidatus Nitrosotenuis (an ammonia-oxidizing archaea) collaborated as the SMX degraders, who carried highly conserved and expressed CuMMOs (pMMO and AMO) for ROS generation, thereby triggering the oxidative degradation of SMX. This study deciphers SMX biodegradation through a fresh perspective of free radical chemistry, and concurrently providing a theoretical framework for the advancement of environmental biotechnologies aimed at OMP removal.

Active sites and structure regulation of non-radical pathways in N-doped graphene-activated persulfate

In this study, we investigated the non-free radical pathways and active sites of N-doped graphene (N-rGO)-activated peroxymonosulfate (PMS). All as-prepared N-rGO samples could activate PMS and develop non-radical pathways. Graphitic-N sites were the major sites for N-rGO activation of PMS, and their content was positively related to the intensity of non-radical pathways. For sulfamethoxazole (SMX), the degradation rate by NH3-rGO-10/PMS and non-radicals within 10 min was 93.66 and 75.34% respectively. In the presence of different anions and different concentrations of humic acid, the removal rate of SMX was still more than 90%.

Low energy consumption pathway to improve sulfamethoxazole degradation by carbon fiber@Fe3O4-CuO: Electrocatalysis activity, mechanism and toxicity

Catalysts play a pivotal role in advanced oxidation processes for the remediation of organic wastewater. In this study, a 3D carbon fiber@Fe3O4-CuO catalyst was fabricated, and its efficacy for persulfate activation to remove sulfamethoxazole (SMX) was investigated at extremely low current density. The results of characterization revealed that the catalyst was uniformly distributed on the carbon fiber, and the loaded catalyst was Fe3O4-CuO nanoparticles with a diameter range of 20–50 nm. The SMX removal rate was significantly enhanced at extremely low current density by the metallic oxide catalyst loaded on carbon fiber. Approximately 90 % of SMX was degraded within 90 min when the electric current density was set at 0.1 mA cm−2. This modification process not only improved the persulfate activation efficiency but also enhanced the generation of hydrogen peroxide. Both radical and non-radical pathways were involved in the degradation of SMX. The degradation pathway mainly included hydroxylation, carboxylation, aniline cleavage, and desulfonation reactions. The quantitative structure–activity relationship model indicated that the potential risk of intermediate products to fish, daphnia, and green algae significantly decreased during the electrocatalytic oxidation process. This study provides a novel strategy for persulfate activation, which can significantly enhance the degradation efficiency, toxicity abatement, and energy usage effectiveness of electrocatalytic technology.

Boosted micropollutant removal over urchin-like structured hydroxyapatite-incorporated nickel magnetite catalyst via peroxydisulfate activation

In this work, urchin-like structured hydroxyapatite-incorporated nickel magnetite (NiFe3O4/UHdA) microspheres were developed for the efficient removal of micropollutants (MPs) via peroxydisulfate (PDS) activation. The prepared NiFe3O4/UHdA degraded 99.0 % of sulfamethoxazole (SMX) after 15 min in 2 mM PDS, having a first-order kinetic rate constant of 0.210 min−1. In addition, NiFe3O4/UHdA outperformed its counterparts, i.e., Fe3O4/UHdA and Ni/UHdA, by giving rise to corresponding 3.6-fold and 8.6-fold enhancements in the SMX removal rate. The outstanding catalytic performance can be ascribed to (1) the urchin-like mesoporous structure with a large specific surface area and (2) the remarkable synergistic effect caused by the redox cycle of Ni3+/Ni2+ and Fe2+/Fe3+ that enhances multipath electron transfers on the surface of NiFe3O4/UHdA to produce more reactive oxygen species. Moreover, the effects of several reaction parameters, in this case the initial solution pH, PDS dosage, SMX concentration, catalyst loading, co-existing MPs and humic acid level on the catalytic performance of the NiFe3O4/UHdA + PDS system were systematically investigated and discussed in detail. The plausible catalytic mechanisms in the NiFe3O4/UHdA + PDS system were revealed via scavenging experiments and electron paramagnetic resonance analysis, which indicated a radical (•OH and SO4•−) as the major pathway and a nonradical (1O2) as the minor pathway for SMX degradation. Furthermore, NiFe3O4/UHdA exhibited fantastic magnetically separation and retained good catalytic activity with a low leached ion concentration during the performance of four cycles. Overall, the prepared NiFe3O4/UHdA with outstanding PDS activation could be a promising choice for the degradation of persistent organic pollutants from wastewater.

Non-radical mediated reduced graphene oxide/polypyrrole catalytic ceramic membrane-PDS system for source control of SMX

The activation of persulfate by a novel heterogeneous metal-free catalyst is of great significance in the efficient degradation of antibiotics. In this study, a novel reduced graphene oxide/polypyrrole ceramic membrane (rGO/PPy CM) integrated with in-situ peroxydisulfate (PDS) activation was operated for sulfamethoxazole (SMX) removal. Membrane confinement effect was used to enhance the interaction among SMX, PDS and catalytic membrane, whose removal rate of SMX reached 95 % after filtration for 10 min. Five-cycle filtration of SMX showed superior stability and reusability with all removal efficiencies above 90 %. Quenching experiments and in-situ open circuit potential testing established that this system maximized the induction of non-radical pathways for SMX degradation. rGO/PPy played a dual role as a PDS activator to form singlet oxygen and as an electron transfer medium. Density functional theory calculations illustrated that the combination of rGO and PPy enhanced the binding force with PDS, promoting non-radical oxidation. The possible degradation pathways of SMX by rGO/PPy CM-PDS system were proposed, including S-N bond cleavage, oxidation, aniline ring cleavage and hydroxylation. In general, this system enhanced the efficiency of PDS activation and SMX removal through membrane confinement and non-radical oxidation, which showed the promise of rGO/PPy CM in water purification.

The environmental risk assessment of constructed wetlands filled with iron and manganese ores in typical antibiotic treatment

Constructed wetlands (CWs) is considered as an efficient and environmentally friendly technology for advanced wastewater treatment to eliminate organic pollutants such as sulfamethoxazole (SMX) and trimethoprim (TMP). Iron (Fe) and manganese (Mn) ores have attracted more and more attention as CWs substrates in treating SMX and TMP, but the potentially negative environmental effects of wetland effluents, ore contaminants leached from the substrates and the risk of transmission of antibiotic resistance genes (ARGs) are still not clear. Three CW groups with different substrates (river sand (C-CW), Fe ore (Fe-CW), and Mn ore (Mn-CW)) were set up to evaluate the average removal rates and environmental risk in treating wastewater containing SMX and TMP. The results showed that the average removal rates of SMX and TMP by Fe-CW and Mn-CW were significantly higher than that of C-CW by 12.46%, 6.59% and 38.93%,15.39% respectively (p < 0.05), suggesting that both Fe and Mn ores facilitated the removal of antibiotics. However, the least abundance of ARGs was found in the layer of Fe ore at the middle layer (ML) in Fe-CW among all CWs, which suggested that Fe ore could reduce the risk of ARGs transmission. Although the environmental risk of Fe-CW and Mn-CW effluent was low, Fe-CW effluent inhibited the growth of Chlorella in both 48h and 72h experiments, while Mn-CW effluent showed an inhibitory effect in 48h and then promoted the growth in 72h. Meanwhile, these findings offer valuable insights for wetland health assessment and substrate selection for CWs.

Unraveling the role of CH3C(=O)OO• in the degradation of emerging organic contaminants via boosting activation of peracetic acid by iron oxychloride catalyst

Activated peracetic acid (PAA) processes have received increasing focus on the removal of various micropollutants. In this study, iron oxychloride (FeOCl) was used to activate PAA for emerging organic contaminants (EOCs) degradation and sulfamethoxazole (SMX) was utilized as the target pollutant. The removal rate of SMX can achieve 90.37% at a neutral condition, and the kobs was 0.0836 min−1. According to the free radical quenching experiment, ESR spectrum, and LC/MS analysis, CH3C(=O)OO• was confirmed to be the main contributor to SMX degradation. The redox cycle of Fe(III)/Fe(II) pairs was the core mechanism of the FeOCl catalysis. A total of six possible transformation products in the FeOCl/PAA system were identified, as well as four possible degradation pathways were proposed. After the FeOCl/PAA treatment, most of the TPs exhibited lower toxicity than SMX itself. The repeatability of FeOCl was still > 80% after four uses, inorganic anions (HCO3– and Cl-) had negligible influences, while humic acid could compete for reactive species and lead to a decrease in the degradation of SMX. Besides, the SMX degradation was almost not affected in the actual water bodies, demonstrating that the FeOCl/PAA process possesses high application potential. The degradation efficiency of FeOCl/PAA systems for other pollutants was also measured, and the removal efficiencies were different due to the selectivity of the CH3C(=O)OO•. Overall, this study comprehensively revealed the oxidation mechanism of the FeOCl/PAA system and provides theoretical support for practical application.

Co single-atom C2N3 activates peroxymonosulfate for efficient degradation of sulfamethoxazole at 4 °C: A combined experimental and density functional theory study

The Fenton-like reactions for antibiotic degradation become very slow at low temperatures. To overcome this inadequacy, we prepared a rare CxNy allotrope, C2N3, by pyrolysis of HNO3 pretreated melamine and loaded with ultrahigh-density Co single atom (SA) to activate peroxymonosulfate (PMS) to remove sulfamethoxazole (SMX). Results showed that the removal rate of SMX reached 100 % at 4 °C within 8 min. The Co/C2N3-650 + PMS system achieved excellent degradation efficiency for simulated wastewater experiments and various interference factors. The catalyst could efficiently degrade a variety of antibiotics, and achieved more efficient degradation rate in alkaline wastewater. Electron paramagnetic resonance (EPR) measurements and quenching tests confirmed the primary role of singlet oxygen (1O2) in SMX degradation with PMS. Density functional theory (DFT) calculation verified the binding energy of CoN3 site and activation pathway for the different oxygen sites of PMS. The linear sweep voltammetry (LSV) and chronopotentiometry analysis revealed that the electrons of PMS were transferred to the CoN3 sites to form SO5•- intermediates, and proved the generation of 1O2 via the SO5•- self-reaction. This work reveals a new mechanism for the formation of 1O2 and opens up novel approach for SA heterogeneous catalysts in advanced oxidation processes (AOPs).

Degradation of Sulfamethoxazole by Manganese(IV) Oxide in the Presence of Humic Acid: Role of Stabilized Semiquinone Radicals.

In this work, we demonstrate for the first time the abatement of sulfamethoxazole (SMX) induced by stabilized ortho-semiquinone radicals (o-SQ•-) in the MnO2-mediated system in the presence of humic acid. To evaluate the performance of different MnO2/mediator systems, 16 mediators are examined for their effects on MnO2 reactions with SMX. The key role of the bidentate Mn(II)-o-SQ• complex and MnO2 surface in stabilizing SQ•- is revealed. To illustrate the formation of the Mn(II)-o-SQ• complex, electron spin resonance, cyclic voltammetry, and mass spectra were used. To demonstrate the presence of o-SQ• on the MnO2 surface, EDTA was used to quench Mn(II)-o-SQ•. The high stability of o-SQ•- on the MnO2 surface is attributed to the higher potential of o-SQ•- (0.9643 V) than the MnO2 surface (0.8598 V) at pH 7.0. The SMX removal rate constant by different stabilized o-SQ• at pH 7.0 ranges from 0.0098 to 0.2252 min-1. The favorable model is the rate constant ln (kobs,7.0) = 6.002EHOMO(o-Qred) + 33.744(ELUMO(o-Q) - EHOMO(o-Qred)) - 32.800, whose parameters represent the generation and reactivity of o-SQ•, respectively. Moreover, aniline and cystine are competitive substrates for SMX in coupling o-SQ•-. Due to the abundance of humic constituents in aquatic environments, this finding sheds light on the low-oxidant-demand, low-carbon, and highly selective removal of sulfonamide antibiotics.

Enhanced hydroxyl radical generation for micropollutant degradation in the In2O3/Vis-LED process through the addition of periodate

Periodate (PI) as an oxidant has been extensively studied for organic foulants removal in advanced oxidation processes. Here PI was introduced into In2O3/Vis-LED process to enhance the formation of ·OH for promoting the degradation of organic foulants. Results showed that the addition of PI would significantly promote the removal of sulfamethoxazole (SMX) in the In2O3/Vis-LED process (from 9.26% to 100%), and ·OH was proved to be the dominant species in the system. Besides, the process exhibited non-selectivity in the removal of different organic foulants. Comparatively, various oxidants (e.g., peroxymonosulfate, peroxydisulfate, and hydrogen peroxide) did not markedly promote the removal of SMX in the In2O3/Vis-LED process. Electrochemical analyses demonstrated that PI could effectively receive photoelectrons, thus inhibiting the recombination of photogenerated electron-hole (e−/h+) pairs. The holes then oxidized the adsorbed H2O to generate ·OH, and the PI converted to iodate at the same time. Additionally, the removal rate of SMX reduced from 100% to 17.2% as Vis-LED wavelengths increased from 440 to 560 nm, because of the low energy of photons produced at longer wavelengths. Notably, the species of PI do not affect its ability to accept electrons, resulting in the degradation efficiency of SMX irrespective of pH (4.0–10.0). The coexistence of inorganic cations and anions (such as Cl−, CO32−/HCO3−, SO42−, Ca2+, and Mg2+) also had an insignificant effect on SMX degradation. Furthermore, the process also showed excellent degradation potential in real water. The proposed strategy provides a new insight for visible light-catalyzed activation of PI and guidance to explore green catalytic processes for high-efficiency removal of various organic foulants.

Efficient electrochemical decomposition of sulfamethoxazole using a novel free-standing TiN anode

The utilization of electrochemical oxidation (EO) processes has become increasingly popular in the field of wastewater treatment, and the robust and sustainable electrode materials were highly desirable for such processes. Among these materials, titanium nitride (TiN) has emerged as a promising candidate due to its unique electronic configuration, which impart ideal electrical conductivity similar to metals, and good stability approaching that of ceramic electrode. This study aimed to develop a free-standing TiN electrode for the EO treatment of refractory antibiotics such as sulfamethoxazole (SMX), and to evaluate its efficacy for SMX removal. The results showed that the TiN electrode achieved a high SMX removal rate (100% removal at 60 min, kobs = 0.031 min−1). Density functional theory (DFT) calculations were utilized to explicate the underlying mechanism, revealing that water oxidation on the TiN surface generates ·OH rather than O2, making TiN an excellent material for the mineralization of recalcitrant SMX. Additionally, both the DFT and LC-MS/MS results demonstrated that the degradation pathway of SMX was induced by ·OH through H-abstraction and electron-transfer pathway, and the active sites responsible for the degradation intermediates were determined by DFT calculation. Overall, these findings provide valuable insights into the development of effective and environmental benign water purification method using novel, free-standing TiN anode material.

DBD plasma coupling MnO2-Fe3O4-cellulose acetate films for sulfamethoxazole degradation: Insight for catalytic ozonation and Fenton effect

In this study, efficient degradation of sulfamethoxazole (SMX) by coupling dielectric barrier discharge (DBD) plasma and MnO2-Fe3O4-cellulose acetate (MnO2-Fe3O4-CA) film catalyst was investigated. SEM, XRD, FT-IR and XPS were carried out to confirm the successful preparation of the MnO2-Fe3O4-CA film. The optimal constitution of MnO2-Fe3O4 and CA was evaluated according to the SMX degradation under different conditions of the prepared films. When 3 % 3:1 MnO2-Fe3O4-CA films were added into the DBD system, the removal rate of SMX could reach 93.55 %. Experiments on the effect of the initial pH value of the solution indicated that the SMX degradation was better under both neutral and alkaline solution conditions. Mechanism analysis show that ·OH, ·O2− and 1O2 were involved in the degradation of SMX. The MnO2-Fe3O4-CA catalyst could burst Fenton reaction and promote ozone decomposition, and accordingly generated more reactive oxygen species (ROS) responsible for the increase of the SMX degradation. The cyclic experiments showed that film had good repeatability and stability. Four routes of SMX degradation were given according to the byproducts analysis, and the toxicity was evaluated.

Enhanced in-situ oxygen evolution and hydrogen peroxide production by a floatable ZnO-incorporated polyurethane photocatalyst for sulfamethoxazole degradation

A highly efficient rigid floatable photocatalyst was prepared by seeding ZnO in polyurethane (PU) and subsequent hydrothermal ZnO coating (P-ZsZc). Compared to pristine ZnO, granular P-ZsZc had an uplifted valence band (VB) and generated new covalent Zn-O-C bond between PU and ZnO, resulting in a significantly enhanced photocorrosion resistance by boosting the mobility of photoexcited holes. In addition, the VB of P-ZsZc was favorable for the in-situ oxygen evolution reaction (OER) and H2O2 production. As a result, the P-ZsZc achieved ∼ 98% removal of sulfamethoxazole (SMX) within 2 h for 5 consecutive cycles. Moreover, the SMX removal rate and Zn(II) leaching remained at ∼ 0.036 min−1 and 0.17 mg L−1, respectively, even during the fifth cycle for 10 h. Furthermore, scavenger experiments and electron spin resonance (ESR) spin trap analysis revealed that the main photogenerated reactive oxygen species (ROS) was H2O2. Floatable P-ZsZc showed constant SMX removal of ∼ 90% in continuous flow experiments (CFEs) for up to 10 h of operation. This study offers a new approach to prepare floatable rigid photocatalysts capable of in-situ oxygen and H2O2 production to degrade organic pollutants.

An anode and cathode cooperative oxidation system constructed with Ee-GF as anode and CuFe2O4/Cu2O/Cu@EGF as cathode for the efficient removal of sulfamethoxazole

This study aimed to further improve the degradation efficiency of pollutants by electrochemical oxidation system and reduce the consumption of electric energy. A simple method of electrochemical exfoliation was used to modify graphite felt (GF) to prepare an anode material (Ee-GF) with high degradation performance. An anode and cathode cooperative oxidation system was constructed with Ee-GF as the anode and CuFe2O4/Cu2O/Cu@EGF as the cathode to efficiently degrade sulfamethoxazole (SMX). Complete degradation of SMX was achieved within 30 min. Compared with anodic oxidation system alone, the degradation time of SMX was reduced by half and the energy consumption was reduced by 66.8 %. The system displayed excellent performance for the degradation of different concentrations (10–50 mg L−1) of SMX, different pollutants, and under different water quality conditions. In addition, the system still maintained 91.7 % removal rate of SMX after ten consecutive runs. At least 12 degradation products and seven possible degradation routes of SMX were generated in the degradation process by the combined system. The eco-toxicity of degradation products of SMX was reduced after the proposed treatment. This study provided a theoretical basis for the safe, efficient, and low energy consumption removal of antibiotic wastewater.

Peroxymonosulfate activation by Mg-introduced Fe-N carbon nanotubes to accelerate sulfamethoxazole degradation: Singlet oxygen-dominated nonradical pathway

Here, Mg-introduced Fe-N carbon nanotube catalysts (FeMg@NCNTs) were prepared for peroxymonosulfate (PMS). Experiments suggested that the introduction of Mg improved the removal of sulfamethoxazole (SMX) and found a transformation from the original radical pathway to a nonradical pathway dominated by singlet oxygen (1O2). XPS characterization demonstrated an enhanced pyridinic N content with the introduction of Mg. SMX degradation was not inhibited by pH, coexisting ions, or humic acid (HA). The free radical scavengers and electron paramagnetic resonance (EPR) indicate that the primary reactive substance was 1O2. Experimentally, 1O2 was proven to have a predominant effect on the degradation of SMX. The concentration of 1O2 increased 6.37 times after the introduction of Mg. Four decomposition pathways and three fragile sites for SMX were proposed by DFT calculations and HPLC-MS. The toxicity estimation software tool (T.E.S.T) analyzed the intermediates with lower ecotoxicity than SMX. The different contaminants (CIP, BPA, TBBPA, TCS, TC and Rh B) had a removal rate of more than 99% at 60 min except TC. The removal rates of SMX in tap water, river water and lake water were 100%, 96.6% and 93.1% in 40 min, respectively. The SMX degradation efficiency remained good after 5 cycles of the experiment. FeMg@NCNTs hydrogel catalyst continuous flow device exceeded 90% within 15 h for SMX removal efficiency and the Rh B is always running at 99% removal rate. In conclusion, this work provides a singlet oxygen-dominated non-radical pathway activating material and provides a new option for antibiotic wastewater degradation and practical applications.

Lithium cobalt oxide with excellent electron mobility: An efficient activator of peroxymonosulfate for the degradation of sulfamethoxazole

Aiming at the problems of sulfamethoxazole (SMX), such as large amount of usage, high degradation difficulty and low removal efficiency of conventional sewage treatment technology, commercial lithium cobalt oxide (LCO) was employed as heterogeneous catalyst to activate peroxymonosulfate (PMS) for SMX degradation in this study. Various characterization methods were applied to investigate the morphology and physicochemical properties of LCO catalysts. Then, complete removal of SMX (2.5 mg/L) was attained within 30 min, the dissolution of cobalt ion was less than 0.1 mg/L, and the removal rate of SMX could still be maintained at 90% after five consecutive cycles, revealing that LCO had outstanding catalytic performance, excellent electron transfer rate, wide operating pH range and good stability. The susceptibility of inorganic anions, diverse water bodies and distinct contaminants to LCO/PMS system was investigated to explore its realistic application. Further exploration demonstrated that the reactive species generated on SMX degradation were sulfate radical (SO4•–) and hydroxyl radical (•OH), in which SO4•– performed a leading role. Integrated with XPS analysis, it was proposed that the Co3+/Co2+ redox companions were the active sites for activating PMS. The possible degradation pathways were put forward by discussing the intermediates of SMX which identified by UPLC-QTOF-MS/MS. In short, this work was conducive to supply a reference for the application of cobalt based doped heterogeneous catalyst in the field of wastewater treatment.

Promoting effect of plant hormone gibberellin on co-metabolism of sulfamethoxazole by microalgae Chlorella pyrenoidosa

In this study, sodium acetate (NaAC) as a co-substrate effectively promoted the metabolism of sulfamethoxazole (SMX) by microalgae Chlorella pyrenoidosa. In the cultivation supplied with 5.0 and 10.0 g L−1 NaAC, 51.1% and 61.2% SMX was removed, respectively. On this basis, the improvement effect of plant hormone gibberellin (GA3) on SMX removal by 5 g L−1 NaAC supplied as co-substrate was further investigated. The results showed that biodegradation played decisive role in the removal of SMX. As a plant hormone, GA3 effectively improved the co-metabolic removal efficiency of SMX by C. pyrenoidosa. Especially when GA3 dosage reached 10.0 and 50.0 mg L−1, C. pyrenoidosa showed a very high SMX removal rate of 83.5% and 95.3%, respectively. Transcriptome analysis showed that GA3 promoted the removal of SMX by C. pyrenoidosa was the result of the combined action of exogenous and endogenous plant hormones.

Effective photocatalytic degradation of sulfamethoxazole using tunable CaCu3Ti4O7 perovskite

Sulfamethoxazole (SMX) is largely prescribed for bacterial infections but raises a major concern over generation of antibiotic-resistant bacteria in the environment. This study employed various perovskite-type photocatalysts, made by two-step synthesis procedures, to remove SMX. The as-synthesized CaCu3Ti4O7 (CCTO) perovskites were characterized by XRD, SEM-EDX, and DLS. Complete degradation (∼99%; kobs = 0.0279 min−1) of SMX was recorded under UV-light irradiation for 90 min in the presence of CCTO. SMX removal rate was investigated under various reaction conditions including pH, catalyst dose, electrolyte (NaCl and NaBr). The astonishing rate of SMX removal (kobs = 0.0614 min−1) was observed with the addition of 50 mM NaBr electrolytes in the reaction, which might imply that the appearance of halogen reactive species. CCTO-MS particles were aggregated in traces when the electrolytes concentration increases, resulting in reduced rate of SMX. The SMX concentration abatement and the formation of possible intermediates during photocatalytic reaction were analyzed. The upshot of this study reveals that the inexpensive and environmentally benign CCTO perovskite photocatalyst could be applied for the treatments of emerging contaminants in the future.