Degradation of sulfamethoxazole in water by solar photo-Fenton. Chemical and toxicological evaluation

Performance and mechanism of sulfamethoxazole removal from seawater in a single-chamber bioelectrochemical system

The aim of this study was to investigate the performance and mechanism of sulfamethoxazole (SMX) biodegradation in seawater using a single-chamber bioelectrochemical system (SCBES). With an initial SMX concentration varying from 1 to 10 mg/L, the SMX removal decreased from 99.1 ± 2.0% to 89.6 ± 8.0% in the SCBES within 120 h under an applied voltage of 0.8 V. The SMX removals could be fitted by the pseudo-first-order equation (R2 > 0.96), which had a kinetic constant of 0.031 h-1 in the SCBES at 1 mg/L SMX. The control tests with a dual-chamber BES showed that the cathodic biofilms had higher SMX removal (97.0 ± 9% vs. 67.4 ± 7%) and S2- accumulation from SO42- reduction (651 ± 65 vs. 427 ± 43 mg/L) than anodic biofilms within 120 h, respectively. Higher bacterial viability and biomass in the cathodic than anodic biofilms of the SCBES resulted in higher performance of the cathodic biofilms (9.1:1 vs. 7.5:1 and 194 ± 30 vs. 76 ± 11 mg·protein/g). The linear relationship between SO42- removals and SMX concentrations (R2 > 0.970) demonstrated that sulfate-reducing bacteria (SRB) could be crucial to the SMX degradation. Desulfuromusa and Desulfococcus as the dominant species were identified in the bacterial communities of the SCBES. The high performance of SCBES may be attributed to the integration of bioelectrochemical reactions with the synergy between electrochemically active bacteria and SRBs. Results from this study showed that SCBES could be a promising way for SMX biodegradation in seawater.

Two birds with one stone: Degradation of pharmaceuticals and elimination of bacteria upon treatment of urban wastewater with a Fenton-like process, based on zero-valent iron at pH 4

ZVI-Fenton, which is the combination of zero-valent iron (metallic Fe) and H2O2 is a relatively cheap advanced oxidation process for the elimination of contaminants from wastewater. Here we experimentally tested the ZVI-Fenton reaction at pH 4 towards two crucial goals in the treatment of secondary (partially treated) urban wastewater: (i) degradation of pharmaceuticals such as anti-inflammatory drugs (ibuprofen) and antibiotics (cefazolin, sulfamethoxazole), and (ii) elimination of a considerable fraction of bacteria through a combination of acidic pH and strongly oxidising conditions. In detail, ZVI-Fenton at pH 4 achieved degradation of both primary contaminants and potentially problematic transformation intermediates. The latter include toxic 4-isobutylacetophenone from ibuprofen and compounds potentially retaining antibiotic properties, namely cefazolin products with an intact β-lactam ring and sulfamethoxazole products retaining the p-amino sulfonic acid moiety. Furthermore, the ZVI-Fenton process significantly lowered the total abundance of bacteria, greatly aiding the final disinfection stage. Overall, both objectives were successfully achieved demonstrating that ZVI-Fenton at pH 4 is an efficient treatment against chemical and microbiological contaminants.

Nitrate Enhanced Sulfamethoxazole Degradation by 222 nm Far-UVC Irradiation: Role of Reactive Nitrogen Species

The application of 222 nm far-UVC irradiation for degrading organic micropollutants in water shows promise. Nitrate (NO3-), found in nearly all water bodies, can significantly impact the performance of 222 nm far-UVC-driven systems. This work was the first to investigate the effect of NO3- on sulfamethoxazole (SMX) photodegradation at 222 nm, finding that NO3- significantly enhances SMX degradation in different dissociated forms. Besides the hydroxyl radical (•OH), reactive nitrogen species (RNS) also played important roles in SMX degradation. With increasing NO3- concentration, the RNS contribution to SMX degradation decreased from 25.7 to 8.6% at pH 3 but increased from 1.5 to 24.7% at pH 7, since the deprotonated SMX with electron-rich groups reacted more easily with RNS. The transformation mechanisms of SMX involving isomerization, bond cleavage, hydroxylation, nitrosation, and nitration processes were proposed. 15N isotope labeling experiments showed that the RNS-induced nitrated products even became the major products of SMX in the 222 nm far-UVC/NO3- system at pH 7 and exhibited a higher toxicity than SMX itself. Further research is necessary to avoid or eliminate these toxic byproducts. This study provides valuable insights for guiding the utilization of 222 nm far-UVC for treating antibiotics in NO3--containing water.

Hydrolysis of sulfamethoxazole in the hyporheic zone: kinetics, factors and pathways

ABSTRACTIt is unknown how antibiotics would behave after entering the hyporheic zone (HZ), which is an area where groundwater and surface water alternate continuously. In this study, the hydrolysis process in the HZ was investigated based on the intermediates identified by HPLC-Q-TOF-MS and FTIR, and the active sites of sulfamethoxazole (SMX) were predicted by density functional theory (DFT). The results showed that the hydrolysis rate of SMX during surface water recharged groundwater reached 38.94%, and the contribution rate of hydroxyl radicals reached 48.35%. In neutral and alkaline environments, SMX hydrolysed more quickly. This is due to the fact that ·OH, as the main precursor of OH-, is much higher in quantity under alkaline conditions. Inorganic anions such as NO3-, HCO3- and CO 3 2 - may inhibit the hydrolysis of SMX by eliminating the reactive oxygen species generated in the HZ. In the process of groundwater recharging to surface water, the concentration of dissolved oxygen (DO) and the rate of SMX hydrolysis gradually reduced. Nitrification, hydroxylation and polymerisation are the main hydrolysis pathways of SMX. The hydrolysis products of SMX in the HZ are more plentiful and have a higher hydrolysis rate compared to the single oxygen environment. The study on the hydrolysis mechanism of SMX in this paper will provide a theoretical basis for the treatment of antibiotic pollution.

Distribution and ecological risk assessment of antibiotics in different freshwater aquaculture ponds in a typical agricultural plain, China

Freshwater aquaculture serves as a significant focal point for antibiotic contamination, yet understanding antibiotic distribution across different aquaculture models and stages remains limited. This study evaluated antibiotic pollution in three distinct freshwater aquaculture models: rice-crayfish coculture, fish aquaculture, and crab-crayfish aquaculture, during various aquaculture stages. Of the 33 target antibiotics, 16 antibiotics were detected, with the total concentrations ranging from 111.81 ng/L to 15,949.05 ng/L in water and 10.11 ng/g to 8986.30 ng/g in sediment. Among these antibiotics, erythromycin and lomefloxacin are prohibited for use in Chinese aquaculture. Dominant antibiotics in water included lincomycin, enrofloxacin, and enoxacin, whereas in sediment, oxytetracycline and erythromycin were predominant. Notably, lincomycin emerged as a dominant antibiotic in aquaculture for the first time. The concentrations of these dominant antibiotics were high compared to other aquaculture settings and exhibited elevated ecological risk. Critical periods for antibiotic contamination in water and sediment were found to be incongruent, occurring during the rainy season in July for water and the dry season in October for sediment. Notably, the rice-crayfish coculture model exerts a good effect in reducing antibiotic pollution. Overall, these findings offer valuable evidence for the healthful and sustainable advancement of aquaculture.

Direct Phototransformation of Sulfamethoxazole Characterized by Four-Dimensional Element Compound Specific Isotope Analysis

The antibiotic sulfamethoxazole (SMX) undergoes direct phototransformation by sunlight, constituting a notable dissipation process in the environment. SMX exists in both neutral and anionic forms, depending on the pH conditions. To discern the direct photodegradation of SMX at various pH levels and differentiate it from other transformation processes, we conducted phototransformation of SMX under simulated sunlight at pH 7 and 3, employing both transformation product (TP) and compound-specific stable isotope analyses. At pH 7, the primary TPs were sulfanilic acid and 3A5MI, followed by sulfanilamide and (5-methylisoxazol-3-yl)-sulfamate, whereas at pH 3, a photoisomer was the dominant product, followed by sulfanilic acid and 3A5MI. Isotope fractionation patterns revealed normal 13C, 34S, and inverse 15N isotope fractionation, which exhibited significant differences between pH 7 and 3. This indicates a pH-dependent transformation process in SMX direct phototransformation. The hydrogen isotopic composition of SMX remained stable during direct phototransformation at both pH levels. Moreover, there was no variation observed in 33S between the two pH levels, indicating that the 33S mass-independent process remains unaffected by changes in pH. The analysis of main TPs and single-element isotopic fractionation suggests varying combinations of bond cleavages at different pH values, resulting in distinct patterns of isotopic fractionation. Conversely, dual-element isotope values at different pH levels did not significantly differ, indicating cleavage of several bonds in parallel. Hence, prudent interpretation of dual-element isotope analysis in these systems is warranted. These findings highlight the potential of multielement compound-specific isotope analysis in characterizing pH-dependent direct phototransformation of SMX, thereby facilitating the evaluation of its natural attenuation through sunlight photolysis in the environment.

Plasma treatment of sulfamethoxazole contaminated water: Intermediate products, toxicity assessment and potential agricultural reuse

The increasing global water demand has prompted the reuse of treated wastewater. However, the persistence of organic micropollutants in inefficiently treated effluents can have detrimental effects depending on the scope of the reclaimed water usage. One example is the presence of sulfamethoxazole, a widely used antibiotic whose interference with the folate synthesis pathway negatively affects plants and microorganisms. The goal of this study is to assess the suitability of a non-thermal plasma-ozonation technique for the removal of the organic pollutant and reduction of its herbicidal effect. Fast sulfamethoxazole degradation was achieved with apparent reaction rate constants in the range 0.21-0.49 min-1, depending on the initial concentration. The highest energy yield (64.5 g/kWh at 50 % removal) exceeds the values reported thus far in plasma degradation experiments. During treatment, 38 degradation intermediates were detected and identified, of which only 9 are still present after 60 min. The main reactive species that contribute to the degradation of sulfamethoxazole and its intermediate products were hydroxyl radicals and ozone, which led to the formation of several hydroxylated compounds, ring opening and fragmentation. The herbicidal effect of the target compound was eliminated with its removal, showing that the remanent intermediates do not retain phytotoxic properties.

Kinetic modelling of colour and turbidity formation in aqueous solutions of sulphamethoxazole degraded by UV/H2O2

The oxidation of sulphamethoxazole medicine (SMX) has been studied by means of UV/H2O2 conducting at a controlled pH between 2.0 and 12.0 and oxidant ratios of 500 mol H2O2/mol SMX. It is verified that operating at pH = 2.0 the highest rates of SMX degradation (74%) and loss of aromaticity (64%) are obtained. During the process, a strong brown tint and high turbidity are generated in the water depending on the pH, as it affects the chemical speciation of the dissociable compounds. The colour intensity of the water increases from pH = 2.0 (light brown, 3.5 NTU) to a maximum value at pH = 4.0 (dark brown, 42 NTU), when the neutral SMX species is almost 100%. Under these conditions, the formation of carboxylic acids (acetic and oxalic) and nitrate ion are minor. Conducting at higher pH, hue decreases, obtaining at pH = 12.0 a light yellow water (5 NTU) when the anionic SMX predominates. Thus, the maximum formation of nitrate ion occurs under these conditions. A pseudo-first order kinetic modelling is proposed for the loss of aromaticity and colour and turbidity formation in water, where the kinetic parameters are expressed as a function of the applied pH, being the pseudo-first-order rate constants (min-1): k a r o m = 0.0005 p H 2 - 0.0106 p H + 0.0707 ; k c o l o u r = 0.0011 p H 2 - 0.02 p H + 0.1125 and kNTU = 0.06 min-1.

Degradation of enrofloxacin by a novel Fe-N-C@ZnO material in freshwater and seawater: Performance and mechanism

In this study, we investigated the doping of Fe-N-C with ZnO (Fe-N-C@ZnO) to enhance its performance in the reduction of biological toxicity and degradation of enrofloxacin (ENR) in seawater. The steady-state/transient fluorescence analysis and free radical quenching test indicated an extremely low electron-hole recombination rate and the generation of reactive oxygen species in Fe-N-C@ZnO, leading to an improvement in the energy efficiency. We compared the ENR degradation efficiencies of Fe-N-C@ZnO and ZnO using both freshwater and seawater. In freshwater, Fe-N-C@ZnO exhibited a slightly higher degradation efficiency (95.00%) than ZnO (90.30%). However, the performance of Fe-N-C@ZnO was significantly improved in seawater compared to that of ZnO. The ENR degradation efficiency of Fe-N-C@ZnO (58.87%) in seawater was 68.39% higher than that of ZnO (34.96%). Furthermore, the reaction rate constant for ENR degradation by Fe-N-C@ZnO in seawater (7.31 × 10-3 min-1) was more than twice that of ZnO (3.58 × 10-3 min-1). Response surface analysis showed that the optimal reaction conditions were a pH of 7.42, a photocatalyst amount of 1.26 g L-1, and an initial ENR concentration of 6.56 mg L-1. Fe-N-C@ZnO prepared at a hydrothermal temperature of 128 °C and heating temperature of 300 °C exhibited the optimal performance for the photocatalytic degradation of ENR. Based on liquid chromatography-mass spectrometry analysis, the degradation processes of ENR were proposed as three pathways: two piperazine routes and one quinolone route.

Degradation of veterinary antibiotics by Fenton process: Products identification and toxicity assessment

The aim of the work was primarily to determine the relationship between the doses of Fenton's reagents and the effectiveness of the ecotoxicity removal of aqueous solutions containing selected antibiotics. The degradation process of ampicillin, doxycycline, and tylosin in an acidic environment in the presence of H2O2 and FeSO4 was studied. The effect of reagent doses on the degree of degradation and identification of antibiotic transformation products was measured by the UPLC qTOF method. The degree of mineralisation was determined based on changes in the concentration of total organic carbon. The ecotoxicity of products was determined with commercial MARA® and MICROTOX® bioassays, as well as against unselected microorganisms from polluted rivers and wastewater treatment plant effluent. It was found that the complete degradation of antibiotics and the simultaneous elimination of the toxicity of the Fenton process products required the use of a precisely defined amount of reagents. When an insufficient dose of reactants was used, the post-reaction solutions contained antibiotic derivatives showing antimicrobial activity. On the other hand, the toxicity of the post-reaction solution against to microbiocenoses was observed when too high doses of H2O2 were used in the process. This effect resulted from the presence of unreacted reagent or other unidentified peroxides.

Influence of water matrix components and peroxide sources on the transformation products and toxicity of tebuthiuron under UVC-based advanced oxidation processes

Coupling of UV-C irradiation to different peroxides (H₂O₂, S₂O₈^2- and HSO₅^-) has great potential to degrade persistent organic compounds due to the formation of HO^• or SO₄^•- species. However, an in-depth comparison between the performance of different UV-C/peroxide processes as a function of (i) target compound degradation, (ii) generated transformation products and (iii) lethal/sub lethal toxicity effects has not yet been performed. To this end a comparison study was carried out to evaluate the effectiveness of different UV-C/peroxide processes using the herbicide tebuthiuron (100 or 500 μg L^-1) as a model pollutant. TBH degradation experiments were performed at lab-scale in real municipal wastewater treatment plant effluent and distilled water. Faster degradation occurred by increasing peroxide concentration from 735 to 2206 μmol L^-1 in the municipal wastewater treatment plant effluent, mainly for S₂O₈^2-. Experiments performed in the presence of peroxide trapping agents - HO^• and SO₄^•- (methoxibenzene) or HO^• (2-propanol) - revealed that oxidation in the UV-C/S₂O₈^2- system occurs mainly through SO₄^•-. Lower toxicity for the MWWTP effluent was obtained after oxidative treatments using hydrogen peroxide or monopersulfate as oxidants which react mainly through HO^• radicals. Two mechanistic pathways were proposed for tebuthiuron degradation: (i) hydrogen abstraction by HO^• (H₂O₂ and HSO₅^-) and (ii) electron transfer by SO₄^•- (S₂O₈^2-). In addition, one unprecedented transformation product was identified. In conclusion, results emphasize the relevance of comparing the degradation of toxic compounds in the presence of different peroxide sources and matrices and simultaneouly evaluating responses chemical and biological endpoints.

A hybrid technique for sulfamethoxazole (SFM) removal using Enterobacter hormaechei HaG-7: Bio-electrokinetic degradation, pathway and toxicity

Prolonged exposure to antibiotics would likely favor the development of antibiotic resistance and their gene transfer among bacterial communities that are responsible for enriched antibiotic resistant microbes. Sulfamethoxazole (SFM) is a commonly used antibiotic that is released into the environment through human and animal wastes. Improper degradation of SFM poses severe threats to mankind and all life forms. The present study aims in analyzing the process and the probability of utilizing bio-electrokinetic degradation for elimination of SFM from artificially contaminated soil employing Enterobacter hormaechei HaG-7. The desired optimal conditions for SFM degradation (∼98%) were observed at SFM initial concentration (100 mg/L) with an inoculum dose (1% v/v) and applied potential voltage (1.5 V) at pH (7). The results indicated efficient and complete degradation of SFM when compared with the conventional biodegradation.

Catalytic ozonation of sulfamethoxazole using low-cost natural silicate ore supported Fe2O3: influencing factors, reaction mechanisms and degradation pathways

A low-cost natural silicate ore supported Fe₂O₃ (FeSO) was synthesized for catalytic ozonation of sulfamethoxazole (SMX). XRD, SEM-EDS, BET, FTIR and XPS results of the FeSO catalyst confirmed that the natural silicate ore was successfully modified with iron oxide. The effects of key factors, such as catalyst dosage, initial solution pH, reaction temperature, inorganic anions and initial concentration, on ozonation degradation were systemically investigated. The degradation rate of SMX (20 mg L^-1) was 88.1% after 30 min, compared with only 35.1% SMX degradation rate in the absence of the catalyst, and the total organic carbon (TOC) removal reached 49.1% after 60 min. Reaction mechanisms revealed that surface hydroxyl groups of FeSO were a critical factor for hydroxyl radical (˙OH) production leading to fast SMX degradation in the ozone decomposition process. The degradation products were detected, and the possible pathways of SMX were then proposed. This study provides guidance for preparing a low-cost catalyst and analyzing the degradation products and pathways of SMX in the ozonation process, which is of significance in practical industrial applications.

Biotransformation of sulfamethoxazole by a novel strain, Nitratireductor sp. GZWM139: Characterized performance, metabolic mechanism and application potential

A novel strain, Nitratireductor sp. GZWM139 capable of efficient removal of SMX was isolated from mariculture sewage, and Nitratireductor was reported to conduct the removal of antibiotics for the first time. Strain GZWM139 exhibited desirable adaptations to environmental factors with SMX removal efficiencies more than 90 % at temperatures of 28-38 °C, pH values of 4.5-8.5, salinities of 20-30 ‰, SMX levels of 1-5 mg/L and shaking speeds of 20-260 rpm. SMX removal was a cooperated process implemented by intracellular enzymes and extracellular enzymes, and was achieved through four proposed biotransformation pathways with the occurrences of demethylation, hydroxylation, nitration, formylation, oxidation, bond cleavage and ring opening. Strain GZWM139 responded to the SMX removal process by altering properties of cell membrane and motivating activities of xenobiotic-metabolizing enzymes and antioxidant system. Genomic analysis proved the existence of functional genes relevant to the SMX removal in strain GZWM139 and provided echoing genetic insights for revealing the SMX removal mechanism. Strain GZWM139 performed efficient detoxification of SMX and accomplished simultaneous removal of SMX and nitrogen in both mariculture sewage and domestic sewage. The findings are significant to the effective elimination of SMX pollution and comprehensive cognitions on metabolic mechanisms of SMX removal.

Study of the Phytoextraction and Phytodegradation of Sulfamethoxazole and Trimethoprim from Water by Limnobium laevigatum

Phytoremediation is an environmentally friendly and economical method for removing organic contaminants from water. The purpose of the present study was to use Limnobium laevigatum for the phytoremediation of water from sulfamethoxazole (SMX) and trimethoprim (TRI) residues. The experiment was conducted for 14 days, in which the loss of the pharmaceuticals in water and their concentration in plant tissues was monitored. Determination of SMX and TRI was conducted using liquid chromatography coupled with tandem mass spectrometry. The results revealed that various factors affected the removal of the contaminants from water, and their bioaccumulation coefficients were obtained. Additionally, the transformation products of SMX and TRI were identified. The observed decrease in SMX and TRI content after 14 days was 96.0% and 75.4% in water, respectively. SMX removal mainly involved photolysis and hydrolysis processes, whereas TRI was mostly absorbed by the plant. Bioaccumulation coefficients of the freeze-dried plant were in the range of 0.043-0.147 for SMX and 2.369-2.588 for TRI. Nine and six transformation products related to SMX and TRI, respectively, were identified in water and plant tissues. The detected transformation products stemmed from metabolic transformations and photolysis of the parent compounds.

Fate of Sulfonamides and Tetracyclines in Meat during Pan Cooking: Focus on the Thermodegradation of Sulfamethoxazole

Although antimicrobials are generally found in trace amounts in meat, the human health risk they bear cannot be ignored. With the ultimate aim of making a better assessment of consumer exposure, this study explored the effects of pan cooking on sulfonamides and tetracyclines in meat. Screening of these antimicrobials in cooked meat was first performed by the European Union Reference Laboratory on the basis of HPLC-MS/MS analyses. A proof of concept approach using radiolabeling was then carried out on the most cooking-sensitive antimicrobial-sulfamethoxazole-to assess if a thermal degradation could explain the observed cooking losses. Degradation products were detected thanks to separation by HPLC and monitoring by online radioactivity detection. HPLC-Orbitrap HRMS analyses completed by 1D and 2D NMR experiments allowed the structural characterization of these degradation compounds. This study revealed that cooking could induce significant antimicrobial losses of up to 45% for sulfamethoxazole. Six potential degradation products of 14C-sulfamethoxazole were detected in cooked meat, and a thermal degradation pattern was proposed. This study highlights the importance of considering the cooking step in chemical risk assessment procedures and its impact on the level of chemical contaminants in meat and on the formation of potentially toxic breakdown compounds.

Current Progress in Natural Degradation and Enhanced Removal Techniques of Antibiotics in the Environment: A Review

Antibiotics are used extensively throughout the world and their presence in the environment has caused serious pollution. This review summarizes natural methods and enhanced technologies that have been developed for antibiotic degradation. In the natural environment, antibiotics can be degraded by photolysis, hydrolysis, and biodegradation, but the rate and extent of degradation are limited. Recently, developed enhanced techniques utilize biological, chemical, or physicochemical principles for antibiotic removal. These techniques include traditional biological methods, adsorption methods, membrane treatment, advanced oxidation processes (AOPs), constructed wetlands (CWs), microalgae treatment, and microbial electrochemical systems (such as microbial fuel cells, MFCs). These techniques have both advantages and disadvantages and, to overcome disadvantages associated with individual techniques, hybrid techniques have been developed and have shown significant potential for antibiotic removal. Hybrids include combinations of the electrochemical method with AOPs, CWs with MFCs, microalgal treatment with activated sludge, and AOPs with MFCs. Considering the complexity of antibiotic pollution and the characteristics of currently used removal technologies, it is apparent that hybrid methods are better choices for dealing with antibiotic contaminants.

Reclaimed wastewater reuse in irrigation: Role of biofilms in the fate of antibiotics and spread of antimicrobial resistance

Reclaimed wastewater associated biofilms are made up from diverse class of microbial communities that are continuously exposed to antibiotic residues. The presence of antibiotic resistance bacteria (ARB) and their associated antibiotic resistance genes (ARGs) ensures also a continuous selection pressure on biofilms that could be seen as hotspots for antibiotic resistance dissemination but can also play a role in antibiotic degradation. In this study, the antibiotic degradation and the abundance of four ARGs (qnrS, sul1, blaTEM, ermB), and two mobile genetic elements (MGEs) including IS613 and intl1, were followed in reclaimed wastewater and biofilm samples collected at the beginning and after 2 weeks of six antibiotics exposure (10 µg L^-1). Antibiotics were partially degraded and remained above lowest minimum inhibitory concentration (MIC) for environmental samples described in the literature. The most abundant genes detected both in biofilms and reclaimed wastewater were sul1, ermB, and intl1. The relative abundance of these genes in biofilms increased during the 2 weeks of exposure but the highest values were found in control samples (without antibiotics pressure), suggesting that bacterial community composition and diversity are the driven forces for resistance selection and propagation in biofilms, rather than exposure to antibiotics. Planktonic and biofilm bacterial communities were characterized. Planktonic cells are classically defined "as free flowing bacteria in suspension" as opposed to the sessile state (the so-called biofilm): "a structured community of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living. surface" as stated by Costerton et al. (1999). The abundance of some genera known to harbor ARG such as Streptococcus, Exiguobacterium, Acholeplasma, Methylophylaceae and Porphyromonadaceae increased in reclaimed wastewater containing antibiotics. The presence of biofilm lowered the level of these genera in wastewater but, at the opposite, could also serve as a reservoir of these bacteria to re-colonize low-diversity wastewater. It seems that maintaining a high diversity is important to limit the dissemination of antimicrobial resistance among planktonic bacteria. Antibiotics had no influence on the biofilm development monitored with optical coherence tomography (OCT). Further research is needed in order to clarify the role of inter-species communication in biofilm on antibiotic degradation and resistance development and spreading.

Transformation products of sulfonamides in aquatic systems: Lessons learned from available environmental fate and behaviour data

Sulfonamides (SUAs) and their transformation products (TPs) contribute to environmental pollution. Importance of research on TPs' properties has been emphasised, e.g. allowing a comprehensive environmental risk assessment of their parent compounds. However, TPs' properties have been discussed in reviews on SUAs only marginally, if at all. For the first time, a scientific literature review aims to discuss the current state of knowledge on SUA-TPs including research gaps, and commonalities of SUA-TPs and TPs in general. Literature on SUA-TPs was consulted systematically to collect data on occurrence, physicochemical properties, degradability, and (eco)toxicity. TPs of 14 SUAs were reviewed, and aspects applicable for TPs in general were identified to guide future handling of TPs as a complex category of compounds. The data of sulfamethoxazole (SMX), the main representative, was analysed in more detail to discuss insights on a chemical level. Literature search resulted in 607 SUA-TPs reported in 222 publications. Only for 4%, 31%, and 35% of these TPs, data on occurrence in aquatic systems, on degradation, and (eco)toxicity, respectively, was found. Several mixtures of SUA-TPs were more ecotoxic than their parent compounds, e.g. 10 of 15 mixtures of SMX-TPs. Only few TPs were tested as single substance. Although several TPs could be eliminated experimentally, their mineralisation rate remained often unknown. Thus, further transformation to persistent TPs could not be ruled out. Standardised biodegradability tests of individual TPs would monitor their mineralisation rate, but are almost completely lacking. Reasons are likely poor availability of TPs, but also the focus on abiotic water treatment. Data assessment demonstrated that data of high significance according to standard methods, e.g. OECD methods for chronic (eco)toxicity and ready biodegradability, is needed to assess environmental risks of prioritised TPs, but also to redesign their parent pharmaceutical for complete environmental mineralisation in a long-term (Benign by Design).

Electro-enhanced sulfamethoxazole degradation efficiency via carbon embedding iron growing on nickel foam cathode activating peroxymonosulfate: Mechanism and degradation pathway

The combination of peroxymonosulfate (PMS) activation by hetero-catalysis and electrolysis (EC) attracted incremental concerns as an efficient antibiotics degradation method. In this work, carbon embedding iron (C@Fe) catalysts growing on nickel foam (NF) composite cathode (C@Fe/NF) was prepared via in-situsolvothermal growth and carbonization method and used to activate PMS toward sulfamethoxazole (SMX) degradation. The EC-[C@Fe/NF(II)]-PMS system exhibited an excellent PMS activation, with 100% SMX removal efficiency achieving within 30 min. Reactive oxygen species (ROS) generation and their roles in SMX degradation were confirmed by quenching experiments and electron paramagnetic resonance. It was found that singlet oxygen (¹O₂) and surface-bound radicals were responsible for SMX degradation, and ¹O₂ contributed the most. Furthermore, the possible SMX degradation pathways were proposed on the base of the detected degradation intermediates and density functional theory (DFT) calculation. Toxicity changes were also assessed by the Ecological Structure Activity Relationships (ESAR). This work provides a practicable strategy for synergistically enhancing PMS activation efficiency and promoting antibiotics removal.

UV/TiO2 Photocatalysis as an Efficient Livestock Wastewater Quaternary Treatment for Antibiotics Removal

Antibiotics are among the most common pharmaceutical compounds, and they have been extensively used for the prevention and treatment of bacterial diseases for more than 50 years. However, merely a small fraction of antibiotics is metabolized in the body, while the rest is discharged into the environment through excretion, which can cause potential ecological problems and human health risks. In this study, the elimination of seventeen antibiotics from real livestock wastewater effluents was investigated by UV/TiO2 advanced oxidation process. The effect of process parameters, such as TiO2 loadings, solution pHs, and antibiotic concentrations, on the efficiency of the UV/TiO2 process was assessed. The degradation efficiency was affected by the solution pH, and higher removal efficiency was observed at pH 5.8 and 9.9, while the catalyst loading had no significant effect on the degradation efficiency. UV photolysis showed a good removal efficiency of the antibiotics. However, the highest removal efficiency was shown by the UV/photocatalyst system due to their synergistic effects. The results showed that more than 90% of antibiotics were removed by UV/TiO2 system during the 60 min illumination, while the corresponding TOC and COD removal was only 10 and 13%, respectively. The results of the current study indicated that UV/TiO2 advanced oxidation processes is a promising method for the elimination of various types of antibiotics from real livestock wastewater effluents.

Lycopene attenuates oxidative stress, inflammation, and apoptosis by modulating Nrf2/NF-κB balance in sulfamethoxazole-induced neurotoxicity in grass carp (Ctenopharyngodon Idella)

All drugs that can penetrate the blood-brain barrier (BBB) may lead to mental state changes, including the widely used anti-infective drug sulfamethoxazole (SMZ). Herein, we investigated whether lycopene (LYC) could ameliorate SMZ-induced brain injury and the postulated mechanisms involved. A total of 120 grass carps were exposed under SMZ (0.3 μg/L, waterborne) or LYC (10 mg/kg fish weight, diet) or their combination for 30 days. Firstly, brain injury induced by SMZ exposure was suggested by the damage of BBB (decreases of Claudins, Occludin and Zonula Occludens), and the decrease of neurotransmitter activity (AChE). Through inducing oxidative stress (elevations of malondialdehyde and 8-hydroxy-2 deoxyguanosine, inhibition of glutathione), SMZ increased the intra-nuclear level of NF-κB and its target genes (TNF-α and interleukins), creating an inflammatory microenvironment. As a positive feed-back mechanism, apoptosis begins with activation of pro-death proteins (Bax/Bcl-2) and activation of caspases (caspase-9 and caspase-3). Meanwhile, a compensatory upregulation of constitutive Nrf2 and its downstream antioxidative gene expression (NAD(P)H Quinone Dehydrogenase 1 and Heme oxygenase 1) and accelerated autophagy (increases of autophagy-related genes and p62 inhibition) were activated as a defense mechanism. Intriguingly, under SMZ stress, LYC co-administration decreased NF-κB/apoptosis cascades and restored Nrf2/autophagy levels. The neuroprotective roles of LYC make this natural compound a valuable agent for prevention SMZ stress in environment. This study suggests that LYC might be developed as a potential candidate for alleviating environmental SMZ stress in aquaculture.

Electrochemical activation of peroxymonosulfate (PMS) by carbon cloth anode for sulfamethoxazole degradation

Electrochemical activation of peroxymonosulfate (PMS) at carbon cloth anode (E (Carbon cloth Anode)/PMS system) was investigated for sulfamethoxazole (SMX) degradation. The results indicated that PMS could be activated at carbon cloth anode during electrolysis, resulting in the improvement of SMX degradation. The degradation efficiency of SMX was facilitated with the higher PMS concentration and current density, respectively. The degradation rate constant of SMX increased with the rising pH from 3.6 to 6.0, and reached the highest value at pH 6.0, and then decreased with further increasing pH to 8.0. The presence of chloride ion (Cl^-, 5-100 mM) significantly enhanced SMX degradation, while addition of humic acid (HA, 1-5 mgC L^-1) inhibited SMX degradation. Addition of carbonate (HCO₃^-, 5-20 mM) had a negligible impact on SMX degradation. Small amounts of phosphate (PO₄^3-, 0-5 mM) could promote degradation, while a large amount of PO₄^3- (10-20 mM) inhibited the degradation. Moreover, the quenching experiments demonstrated that sulfate radical (SO₄·^-), hydroxyl radical (·OH) and singlet oxygen (¹O₂) contributed to SMX degradation in E (Carbon cloth Anode)/PMS system. The degradation intermediates of SMX were identified by LC-MS/MS and the degradation pathways were deduced to be hydroxylation, the cleavage of S-N bond, and oxidation of aniline group. Moreover, the micronucleus test of Vicia faba root tips indicated that the E (Carbon Cloth Anode)/PMS system could reduce the genetic toxicity of SMX contaminated water to some extent.

Removal of sulfamethoxazole by ferrous iron activation of persulfate: Optimization of dosing strategy and degradation mechanism

In this paper, the degradation of sulfamethoxazole (SMX) was investigated using the ferrous iron (Fe²⁺) activation of persulfate (PS) (the Fe²⁺/PS process). The influence of the initial concentration of both PS and Fe²⁺ was investigated. It was found that increasing the PS concentration resulted in a higher SMX degradation efficiency. The influence of inhibiting reactions was found to increase with increasing Fe²⁺ concentration. In order to minimize these inhibiting reactions, different dosing strategies were applied. It was found that the SMX degradation efficiency could be enhanced significantly when changing from direct dosing (total amount of Fe²⁺ dosed at the start) to sequential dosing (dosing that same total amount but divided over specific time intervals) and even more when using continuous dosing (dosing the same total amount but continuously over 30 min reaction time). The contribution of different reactive species in this process was also investigated. It was found that hydroxyl radicals (•OH) were mainly responsible for the degradation of SMX during direct dosing, while using continuous dosing of Fe²⁺, the contribution of Fe(IV) and sulfate radicals (•SO₄^-) became more important (reduction of •OH contribution from 89 to 71%). Some degradation products formed during the SMX degradation process were identified and the difference in reaction mechanism between •OH on the one hand and Fe(IV) and •SO₄^- on the other hand was elucidated. At last, a comparison of different sulfate radical based advanced oxidation processes (SR-AOP) is performed by comparing the difference in SMX degradation efficiency, reactive species contribution and the formed degradation products. In most investigated processes, similar degradation products have been found, however, the large •OH contribution in the Fe²⁺/PS process resulted in distinct degradation products.

Coupling of spectrometric, chromatographic, and chemometric analysis in the investigation of the photodegradation of sulfamethoxazole

A workflow is proposed for the study of the photodegradation process of the sulfamethoxazole (SMX) based on the combination of different experimental techniques, including liquid chromatography, mass spectrometry, UV-Visible spectrophotometry, and the treatment of all the analytical data with advanced chemometric methods. SMX, which is one of the most widely used antibiotics worldwide and has been found at remarkable concentrations in various rivers and effluents over all Europe, was degraded in the laboratory under a controlled source of UV radiation, which simulates the environmental solar radiation (Suntest). Kinetic monitoring of the photodegradation process was performed using UV-Visible spectrophotometric measurements and by further Liquid Chromatography with Diode Array Detector and Mass Spectrometry analysis (LC-DAD-MS). Additionally, the acid-base properties were also investigated to see how the pH can affect the speciation of this substance during the photodegradation process. Based on the Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) application, the proposed chemometric method coped with the large amounts of data generated by the different analytical techniques used to monitor the evolution of the photodegradation process. Their simultaneous analysis involved applying a data fusion strategy and an advanced MCR-ALS constrained analysis, which allowed and improved the description of the complete degradation process, detecting the different species of the reaction, and identifying the possible transformation products formed. A total number of six species were resolved in the degradation process of SMX. In addition to the initial SMX, a second species corresponded to a conformational isomer, and the other four species represented different photoproducts, which have also been identified. Furthermore, three different acid-base species of SMX were obtained, and their pK_a values were estimated.

Quantification of photocatalytically-generated hydrogen peroxide in the presence of organic electron donors: Interference and reliability considerations

Photocatalytic H₂O₂ production is an innovative on-site H₂O₂ synthesis method to treat organic pollutants through Fenton-like reactions, avoiding the need and potential liability of H₂O₂ storage and transportation. Accurate quantification of H₂O₂ is crucial to explore the mechanism of photocatalytic H₂O₂ production and optimize reaction parameters. In this work, three common H₂O₂ quantification methods (i.e., titration with potassium permanganate (KMnO₄), and colorimetry with ammonium metavanadate (NH₄VO₃) or N,N-diethylp-phenylenediamine-horseradish peroxidase (DPD-POD)) were compared and their susceptibility to interference by seven types of representative organics were considered. Interference mechanisms were explored based on the electron-donating (E_gap) and electron-accepting (E_LUMO) ability of the present organics. The accuracy of the KMnO₄ titration method is greatly compromised by aromatic compounds even at 0.1 mM due to the increased KMnO₄ consumption by direct oxidation. The presence of p-benzoquinone that directly reacts with NH₄VO₃ and DPD compromises these colorimetric methods, especially DPD-POD colorimetry at concentrations as low as 0.1 mM. The DPD-POD method should also be scrutinized in the presence of phenols due to significant disturbance by oxidation byproducts (e.g. hydroquinone inducing immediate color disappearance). A flowchart was generated to provide guidelines for selecting an appropriate H₂O₂ quantification method for different water matrices treated by Fenton-like reactions.

Abiotic transformation and ecotoxicity change of sulfonamide antibiotics in environmental and water treatment processes: A critical review

Sulfonamides (SAs) are among the most widely used antibiotics to treat bacterial infections for humans and animals. They are also used in livestock agriculture to improve growth and feed efficiency in many countries. Recent years, there is a growing concern about the environmental fate and treatment technologies of SAs, in order to eliminate their potential impact on the ecosystem and human health. Additionally, SAs are frequently used as model compounds to evaluate the performance of newly developed advanced water treatment processes. Hence, understanding the chemical reaction features of SAs can provide valuable information for further technological development. In this review, the reaction kinetics, abiotic transformations and corresponding ecotoxicity changes of SAs in natural environments and water treatment processes were comprehensively analyzed to draw critical suggestion and new insights. The •OH-based AOP is proposed as an effective method for the elimination of SAs toxicity, although it is susceptible to water constituent due to low selectivity. The application of biochar or metal-based oxidants in AOPs is becoming a future trend for SA treatment. Overall, this review would provide useful information for the development of advanced water treatment technologies and the control of ecological risks related to SAs.

The Deuterated "Magic Methyl" Group: A Guide to Site-Selective Trideuteromethyl Incorporation and Labeling by Using CD3 Reagents

In the field of medicinal chemistry, the precise installation of a trideuteromethyl group is gaining ever-increasing attention. Site-selective incorporation of the deuterated "magic methyl" group can provide profound pharmacological benefits and can be considered an important tool for drug optimization and development. This review provides a structured overview, according to trideuteromethylation reagent, of currently established methods for site-selective trideuteromethylation of carbon atoms. In addition to CD3 , the selective introduction of CD2 H and CDH2 groups is also considered. For all methods, the corresponding mechanism and scope are discussed whenever reported. As such, this review can be a starting point for synthetic chemists to further advance trideuteromethylation methodologies. At the same time, this review aims to be a guide for medicinal chemists, offering them the available C-CD3 formation strategies for the preparation of new or modified drugs.

Degradation of sulfamethoxazole by ozonation combined with ionizing radiation

In this study, the degradation and mineralization of sulfamethoxazole (SMX) by ozonation and ionizing radiation were investigated respectively, and the performance of the combined process of ozonation and ionizing radiation was evaluated. Results showed that complete degradation of SMX could be obtained by ozonation in 12 min or by ionizing radiation with the absorbed dose of 1.5 kGy. However, the mineralization of SMX was very limited in ozonation and ionizing radiation system, TOC removal efficiency was less than 15% and 27% in single-ozonation and single-radiation process, respectively. The combination of ozonation and radiation process obviously enhanced the mineralization of SMX, TOC removal efficiency increased to 65.7%. Moreover, the ozonation-radiation process also exhibited good performance in the mineralization of sulfamethazine (SMT) and sulfanilamide (SM), suggesting a good application prospect of the combined process in treating wastewater contaminated with antibiotics. In addition, some different intermediate products were identified during SMX degradation in ozonation process and ionizing radiation process by a high-performance liquid chromatography-mass spectrometry (LC-MS), and possible pathways of SMX degradation by ozonation and radiation were proposed.

Biosynthesized Schwertmannite@Biochar composite as a heterogeneous Fenton-like catalyst for the degradation of sulfanilamide antibiotics

Schwertmannite was successfully loaded onto biochar (Sch@BC) using a biosynthetic method. The physicochemical properties and structural morphology of Sch@BC were explored using XRD, SEM, BET, and XPS. The results showed that introducing biochar can effectively prevent the agglomeration of Sch. The catalytic activity of Sch@BC in the Fenton-like degradation of sulfamethoxazole (SMX) was also systematically investigated under different reaction conditions. Under optimum conditions ([SMX] = 10 mg L^-1, [H₂O₂] = 2.0 mM, Sch@BC = 1.0 g L^-1 and initial pH = 3.0), the removal efficiencies of the SMX and total organic carbon (TOC) were 100% and 45.9%, respectively, within 60 min of the reaction. The results of the radical scavenger effect and ESR studies suggested that the SMX degradation in the Sch@BC/H₂O₂ system was dominated by a heterogeneous Fenton-like reaction. The repeated use of Sch@BC for SMX degradation demonstrated its reusability and stability in Fenton-like reactions. There was also speculation about the degradation mechanism and pathways of SMX. Furthermore, under the same conditions, the removal efficiencies of sulfadiazine (SD) and sulfisoxazole (SIZ) under Fenton-like degradation in the Sch@BC system were 91% and 93%. The results provide a theoretical basis and practical guidance for the creation of a new catalyst using biochar as a support material for the degradation of sulfanilamide antibiotics.

Reusable Fe3O4/SBA15 Nanocomposite as an Efficient Photo-Fenton Catalyst for the Removal of Sulfamethoxazole and Orange II

Today, the presence of recalcitrant pollutants in wastewater, such as pharmaceuticals or other organic compounds, is one of the main obstacles to the widespread implementation of water reuse. In this context, the development of innovative processes for their removal becomes necessary to guarantee effluent quality. This work presents the potentiality of magnetic nanoparticles immobilized on SBA-15 mesoporous silica as Fenton and photo-Fenton catalysts under visible light irradiation. The influence of the characteristics of the compounds and nanoparticles on the removal yield was investigated. Once the key aspects of the reaction mechanism were analyzed, to evaluate the feasibility of this process, an azo dye (Orange II) and an antibiotic (sulfamethoxazole) were selected as main target compounds. The concentration of Orange II decreased below the detection limit after two hours of reaction, with mineralization values of 60%. In addition, repeated sequential experiments revealed the recoverability and stability of the nanoparticles in a small-scale reactor. The benchmarking of the obtained results showed a significant improvement of the process using visible light in terms of kinetic performance, comparing the results to the Fenton process conducted at dark. Reusability, yield and easy separation of the catalyst are its main advantages for the industrial application of this process.

Unprecedented Treatment Strategy of Aquatic Environments: Oxidative Degradation of Penicillin G by Chromium Trioxide in Acidic Media and the Impact of Metal Ion Catalysts: Kinetics and Mechanistic Insights

Degradation kinetics and pathways of the antibiotic penicillin G (Pen) have been examined via oxidation by chromium trioxide (CrVI) in aqueous sulfuric and perchloric acid media. The oxidation reactions were monitored by spectrophotometry at 298 K. In both acidic media, penicillin G oxidation was set to proceed through acid catalysis. The stoichiometry of the reactions designated that 3 moles of Pen required 2 moles of CrVI. The kinetics of Pen oxidation in both acids was of the first order with regard to [CrVI] and less-than unity order with regard to [Pen] and [H+] in their variation. The rates of reactions displayed negligible impacts upon altering ionic strengths or dielectric constants of the reaction media. There was no intrusion of free radicals throughout the redox reactions. Addition of low concentrations of Ni2+, Cu2+, and Zn2+ ions enhanced the oxidation rates, while addition of Cr3+ as a described product did not noteworthily alter the rates. Under comparable investigational circumstances, the oxidation rates in HClO4 were almost 2-fold greater than in H2SO4. The oxidation products of penicillin G were identified by spectral analysis and spot tests as phenyl acetic acid, 2-formyl-5,5-dimethyl-thiazolidine-4-carboxlate ion, ammonium ion, and carbon dioxide. Reliance of reaction rates on temperature has been explored, and the activation and thermodynamic parameters were estimated and debated. In view of the noted reactions' orders and products' identification, a plausible mechanism for the oxidation reactions was suggested. The derived rate law was set to be in accordance with the acquired results. This study offers an unprecedented simple and low-cost treatment method for removal or degradation of certain pollutants for protecting the environment and human health.

A critical review on advanced oxidation processes for the removal of trace organic contaminants: A voyage from individual to integrated processes

Advanced oxidation processes (AOPs), such as photolysis, photocatalysis, ozonation, Fenton process, anodic oxidation, sonolysis, and wet air oxidation, have been investigated extensively for the removal of a wide range of trace organic contaminants (TrOCs). A standalone AOP may not achieve complete removal of a broad group of TrOCs. When combined, AOPs produce more hydroxyl radicals, thus performing better degradation of the TrOCs. A number of studies have reported significant improvement in TrOC degradation efficiency by using a combination of AOPs. This review briefly discusses the individual AOPs and their limitations towards the degradation of TrOCs containing different functional groups. It also classifies integrated AOPs and comprehensively explains their effectiveness for the degradation of a wide range of TrOCs. Integrated AOPs are categorized as UV irradiation based AOPs, ozonation/Fenton process-based AOPs, and electrochemical AOPs. Under appropriate conditions, combined AOPs not only initiate degradation but may also lead to complete mineralization. Various factors can affect the efficiency of integrated processes including water chemistry, the molecular structure of TrCOs, and ions co-occurring in water. For example, the presence of organic ions (e.g., humic acid and fulvic acid) and inorganic ions (e.g., halide, carbonate, and nitrate ions) in water can have a significant impact. In general, these ions either convert to high redox potential radicals upon collision with other reactive species and increase the reaction rates, or may act as radical scavengers and decrease the process efficiency.

Reduced graphene oxide-TiO2/sodium alginate 3-dimensional structure aerogel for enhanced photocatalytic degradation of ibuprofen and sulfamethoxazole

In this study, graphene oxide and titanium dioxide in combination with sodium alginate were used to synthesize the reduced graphene oxide-TiO₂/sodium alginate (RGOT/SA) aerogel. The potential of RGOT/SA aerogel was evaluated for the photocatalytic degradation of ibuprofen and sulfamethoxazole and was compared with that of bare titanium dioxide nanoparticles. More than 99% removal of both the contaminants was obtained within 45-90 min by using the RGOT/SA aerogel under UV-A light. Mineralization of both the pollutants was also higher in case of RGOT/SA aerogel as compared to bare TiO₂ nanoparticles. The optimal mass ratio of TiO₂ nanoparticles with respect to graphene oxide was 2:1 in RGOT/SA aerogel in the presence of 1 wt% sodium alginate solution. High photodegradation of Ibuprofen was observed at neutral pH and acidic to neutral pH was found suitable for the photodegradation of sulfamethoxazole. Three-dimensional interconnected macroporous assembly, large surface area for settling TiO₂ nanoparticles, efficient charge partitioning, and enhanced physical and chemical adsorption of ibuprofen and sulfamethoxazole on the surface of RGOT/SA aerogel were the significant characteristics of RGOT/SA aerogels. Moreover, ease of separation and recyclability of the RGOT/SA aerogel could further save the extra energy used to separate nanoparticles from the effluent.

Elimination of representative fluoroquinolones, penicillins, and cephalosporins by solar photo-Fenton: degradation routes, primary transformations, degradation improvement by citric acid addition, and antimicrobial activity evolution

This work studies the degradation of seven representative antibiotics (ciprofloxacin, norfloxacin, levofloxacin, oxacillin, cloxacillin, cefalexin, and cefadroxil) by solar photo-Fenton process. The removal of antibiotics by the individual components (i.e., light, H₂O₂, or Fe (II)) and the complete photochemical system (light/H₂O₂/Fe (II)) was initially evaluated. Then, the effect of citric acid addition to the photo-Fenton system was assessed. In the third place, the primary transformation products for two illustrative cases (ciprofloxacin and oxacillin treated by photo-Fenton) were determined. Also, photo-Fenton in the presence of citric acid was applied to remove antibiotics from a simulated hospital wastewater. It was found that the solar light component induced degradation of ciprofloxacin, norfloxacin, and levofloxacin, but the rest of the considered antibiotics were not reduced by photolysis. In turn, the photo-Fenton system showed a degrading action on all the tested antibiotics. The addition of citric acid to the system significantly increased the removal of antibiotics. Initial degradation products indicated that hydroxyl radical attacked moieties of antibiotics responsible for their antimicrobial activity. Finally, the treatment of hospital wastewater evidenced the high potentiality of photo-Fenton process for degrading antibiotics in aqueous matrices containing elevated concentrations of citric acid.

Spin Coating Immobilisation of C-N-TiO2 Co-Doped Nano Catalyst on Glass and Application for Photocatalysis or as Electron Transporting Layer for Perovskite Solar Cells

Producing active thin films coated on supports resolves many issues of powder-based photo catalysis and energy harvesting. In this study, thin films of C-N-TiO2 were prepared by dynamic spin coating of C-N-TiO2 sol-gel on glass support. The effect of spin speed and sol gel precursor to solvent volume ratio on the film thickness was investigated. The C-N-TiO2-coated glass was annealed at 350 °C at a ramping rate of 10 °C/min with a holding time of 2 hours under a continuous flow of dry N2. The C-N-TiO2 films were characterised by profilometry analysis, light microscopy (LM), and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The outcomes of this study proved that a spin coating technique followed by an annealing process to stabilise the layer could be used for immobilisation of the photo catalyst on glass. The exposure of C-N-TiO2 films to UV radiation induced photocatalytic decolouration of orange II (O.II) dye. The prepared C-N-TiO2 films showed a reasonable power conversion efficiency average (PCE of 9%) with respect to the reference device (15%). The study offers a feasible route for the engineering of C-N-TiO2 films applicable to wastewater remediation processes and energy harvesting in solar cell technologies.

Sulfamethoxazole Removal from Drinking Water by Activated Carbon: Kinetics and Diffusion Process

Sulfamethoxazole (SMX), a pharmaceutical residue, which is persistent and mobile in soils, shows low biodegradability, and is frequently found in the different aquatic compartments, can be found at very low concentrations in water intended for human consumption. In conditions compatible with industrial practices, the kinetic reactivity and performance of tap water purification using activated carbon powder (ACP) are examined here using two extreme mass ratios of SMX to ACP: 2 µg/L and 2 mg/L of SMX for only 10 mg/L of ACP. In response to surface chemistry, ACP texture and the intrinsic properties of SMX in water at a pH of 8.1, four kinetic models, and two monosolute equilibrium models showed a total purification of the 2 µg/L of SMX, the presence of energetic heterogeneity of surface adsorption of ACP, rapid kinetics compatible with the residence times of industrial water treatment processes, and kinetics affected by intraparticle diffusion. The adsorption mechanisms proposed are physical mechanisms based mainly on π-π dispersion interactions and electrostatic interactions by SMX-/Divalent cation/ArO- and SMX-/Divalent cation/ArCOO- bridging. Adsorption in tap water, also an innovative element of this study, shows that ACP is very efficient for the purification of very slightly polluted water.

Individual and simultaneous degradation of sulfamethoxazole and trimethoprim by ozone, ozone/hydrogen peroxide and ozone/persulfate processes: A comparative study

This study investigates the individual and simultaneous degradation and mineralization of the antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP) in aqueous solution by ozonation, ozone-activated persulfate (PS) and hydrogen peroxide (H₂O₂) processes. The trials were carried out in a semi-continuous column bubble reactor with an ozone diffuser located at the bottom of the column for a period of 2 h. Furthermore, the efficiency of studied processes were evaluated at two different initial pH and various doses of oxidants. The target compounds degradation observed pseudo-first-order rate constants (k_obs) and removal of total organic carbon (TOC) using ozone-based oxidation processes were compared. Irrespective of the applied processes, the mineralization of target compounds was less effective than their degradation in both individual and simultaneous systems. The highest antibiotics degradation rate constants were observed for individual oxidation of TMP (k_obs = 0.379 min^-1) and SMX (k_obs = 0.367 min^-1) at alkaline initial pH (pH₀) in the O₃/H₂O₂ system at an [antibiotic]/H₂O₂ molar ratio of 1/1. Irrespective of the antibiotic studied, the most effective TOC removal (~44%) was observed after a 2-h treatment with the O₃/H₂O₂ system at an [antibiotic]/H₂O₂ molar ratio of 1/5 (pH₀ 10.9). The O₃/PS system at an [antibiotic]/PS molar ratio of 1/5 (pH₀ 10.9) proved the most effective system for both mineralization and degradation (k_obs values of 0.294 min^-1 and 0.266 min^-1) of TMP and SMX, respectively, during the simultaneous oxidation of SMX-TMP. The decomposition by-products of SMX and TMP in studied ozone-based processes were identified using LC-MS analysis. The results of this study strongly suggest that using the O₃/PS process is a promising solution to reduce SMX-TMP contamination in water matrices.

Ferrous metal-organic frameworks with strong electron-donating properties for persulfate activation to effectively degrade aqueous sulfamethoxazole

Three novel persulfate activators, Fe(II)-based metal-organic frameworks (MOFs) were synthesized for the degradation of sulfamethoxazole (SMX). The degradation experiment results showed that all the Fe(II)MOFs could effectively activate persulfate and degrade more than 97% SMX within 180 min, with higher than 77% persulfate decomposition efficiencies. It was found by Mössbauer spectra that the variation of organic ligands for synthesis have an influence on the content of Fe(II) of these MOFs, thus resulted in the order of activation capacities: Fe(Nic) > Fe(PyBDC) > Fe(PIP). It was demonstrated that the activation of persulfate was mainly ascribed to the heterogeneous process that accomplished by surface-bounded Fe(II) acted as the main active site to provided electrons for persulfate or dissolved oxygen. EPR and molecular probe studies confirmed the coexistence of SO₄·^-, ·OH, and O₂·^-, and differentiated their contributions in SMX degradation. Possible degradation pathways of SMX were proposed based on the detection results of intermediates by UPLC-MS/MS. This work provides a new prospect into the synthesis of high-performance MOFs with strong electron-donating properties as efficient persulfate activators, which may encourage the employ of MOFs in the wastewater treatment process.