Sulfamethoxazole Molecules Research Articles

Platinum oxide-based peracetic acid activation for efficient degradation of typical antibiotic

Peracetic acid (PAA)-based Advance Oxidation Process (AOP) is now used to treat pharmaceutically contaminated wastewater. Herein, PAA is heterogenically activated to degrade sulfamethoxazole (SMX) taking platinum oxide (PtO2) as a catalyst for the first time. PtO2/PAA system with good synergetic effect achieved 100 % SMX degradation in 75 min.Its corresponding kinetic rate constant (0.072 min−1) was exceptionally higher than six other Transition Metal/PAA-based systems tested as well as than PtO2 or PAA alone. The degradation improved by augmenting PAA and PtO2 inputs. Radical scavenging and electron paramagnetic resonance pointed acetylperoxy (CH3C(O)OO·) and acetoxyl (CH3C(O)O·) as the main reactive radicals attributing SMX abatement. X-ray photoelectron spectroscopy and diffraction along with electrochemical tests (cyclic voltammetric curve, electrochemical impedance spectra, and I-t curve) recommended that the electron transfer of Pt2+/Pt4+ also facilitated PAA activation. Density Functional Theory (DFT) assisted in predicting the reaction sites on SMX molecules. Four degradation pathways are proposed with the help of DFT calculations and eight intermediate products identified by High-Performance Liquid Chromatography Mass-Spactrometry. Dissolved organic matter, anions and different waterbodies had tolerable degradation inhibition. Efficient reactivity and adequate stability attest PtO2 as an ideal catalyst for oxidative degradations. The findings offer valuable insights into a novel, sustainable, and efficient approach to treat drug-contaminated wastewater.

In-situ Profiling of Environmental Hazardous Sulfamethoxazole in Aquatic and Artificial Saliva samples Using Perovskite Structured Bismuth Ferrite Incorporated Halloysite Nanotubes

Sulfamethoxazole (SMX), a widely used antibiotic, poses significant environmental and health risks due to its persistence and mobility in water systems, potentially leading to antibiotic resistance and ecological harm. Herein, we developed an electrochemical sensor based on Bismuth Ferrite (BiFeO3)/Halloysite Nanotube (BFO/HNT) composite for sensitive and selective SMX detection. The BFO/HNT composite was synthesized via a hydrothermal method and comprehensively characterized using EDS mapping, HRTEM, XRD, FT-IR, and XPS analysis. The BFO/HNT composite enhances the sensor’s performance due to its unique properties, such as increased electrochemical surface area (ECSA) and efficient electron transfer capability. The B-cation (Fe) in the BiFeO3 matrix plays a crucial role in boosting the electrochemical response by facilitating redox reactions. In addition, the HNTs provide a high surface area and excellent adsorption capabilities, which improve the sensor’s sensitivity by facilitating better interaction with SMX molecules. As the results, the prepared sensor demonstrates an impressive linear detection range of 0.01 to 2 µM and 22 to 122 µM, with a detection limit as low as 0.017 µM. Practical applications were validated by detecting SMX in tap water and artificial saliva, achieving high recovery rates of 98.87 % and 99.11 %.

Preparation of catalytic ceramic nanofiber membranes with MnFe dual-active sites enhancing catalytic ozonation of sulfamethoxazole

Membrane-based catalytic ozonation has recently attracted significant attention for its simultaneous boosted contaminant degradation and separation. In this work, catalytic ceramic nanofiber membranes ((MnFe0.05)@CNM) with MnFe dual-active site are prepared by anchoring FeOx nanoparticles onto Mn@CNM via an impregnation and in-situ precipitation method. The (MnFe0.05)@CNM coupled with catalytic ozonation was applied to the degradation of sulfamethoxazole (SMX), achieving a removal rate of up to 99.2 %. The catalytic degradation of SMX is verified by reactive oxygen species (ROS) quenching and EPR detection experiments, which shows that the 1O2, ·OH and O2·- are involved. Furthermore, (MnFe0.05)@CNM demonstrates superior catalytic stability, redox properties, and an abundance of acidic sites, as are revealed by H2-TPR and NH3-TPD analysis. The boosted performance is attributed to the synergistic catalysis by Mn and Fe bimetals under nano-confinement effect of membrane pores through facilitated electron transfer between Mn2+, Mn3+, Mn4+, Fe2+, and Fe3+, and promoting the decomposition of ozone and the generation of ROS. The nano-confinement effect of (MnFe0.05)@CNM also reduces the mass transfer distance between ROS and SMX, promoting ROS to attack the SMX molecules. This study presents a novel approach to developing catalytic ceramic membranes for the enhanced degradation of emerging contaminants in water.

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.

Adsorption Properties of Magnetic Phosphorous Camellia Oleifera Shells Biochar to Sulfamethoxazole in Water

Magnetic phosphorous biochar （MPBC） was prepared from Camellia oleifera shells using phosphoric acid activation and iron co-deposition. The materials were characterized and analyzed through scanning electron microscopy （SEM）， X-ray diffractometry （XRD）， specific surface area and pore size analysis （BET）， Fourier infrared spectroscopy （FT-IR）， and X-ray photoelectron spectroscopy （XPS）. MPBC had a high surface area （1 139.28 m2·g-1） and abundant surface functional groups， and it could achieve fast solid-liquid separation under the action of an external magnetic field. The adsorption behavior and influencing factors of sulfamethoxazole （SMX） in water were investigated. The adsorbent showed excellent adsorption properties for SMX under acidic and neutral conditions， and alkaline conditions and the presence of CO32- had obvious inhibition on adsorption. The adsorption process conformed to the quasi-second-order kinetics and Langmuir model. The adsorption rate was fast， and the maximum adsorption capacity reached 356.49 mg·g-1. The adsorption process was a spontaneous exothermic reaction， and low temperature was beneficial to the adsorption. The adsorption mechanism was mainly the chemisorption of pyrophosphate surface functional groups （C-O-P bond） between the SMX molecule and MPBC and also included hydrogen bonding， π-π electron donor-acceptor （π-πEDA） interaction， and a pore filling effect. The development of MPBC adsorbent provides an effective way for resource utilization of waste Camellia oleifera shells and treatment of sulfamethoxazole wastewater.

Enhanced Oxidation of Organic Compounds by the Ferrihydrite-Ferrate System: The Role of Intramolecular Electron Transfer and Intermediate Iron Species.

Previous studies mostly held that the oxidation capacity of ferrate depends on the involvement of intermediate iron species (i.e., FeIV/FeV), however, the potential role of the metastable complex was disregarded in ferrate-based heterogeneous catalytic oxidation processes. Herein, we reported a complexation-mediated electron transfer mechanism in the ferrihydrite-ferrate system toward sulfamethoxazole (SMX) degradation. A synergy between intermediate FeIV/FeV oxidation and the intramolecular electron transfer step was proposed. Specifically, the conversion of phenyl methyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO2) suggested that FeIV/FeV was involved in the oxidation of SMX. Moreover, based on the in situ Raman test and chronopotentiometry analysis, the formation of the metastable complex of ferrihydrite/ferrate was found, which possesses higher oxidation potential than free ferrate and could achieve the preliminary oxidation of organics via the electron transfer step. In addition, the amino group of SMX could complex with ferrate, and the resulting metastable complex of ferrihydrite/ferrate would combine further with SMX molecules, leading to intramolecular electron transfer and SMX degradation. The ferrate loss experiments suggested that ferrihydrite could accelerate the decomposition of ferrate. Finally, the effects of pH value, anions, humic acid, and actual water on the degradation of SMX by ferrihydrite-ferrate were also revealed. Overall, ferrihydrite demonstrated high catalytic capacity, good reusability, and nontoxic performance for ferrate activation. The ferrihydrite-ferrate process may be a green and promising method for organic removal in wastewater treatment.

Insight into cobalt substitution in LaFeO3-based catalyst for enhanced activation of peracetic acid: Reactive species and catalytic mechanism

In this study, a hollow sphere-like Co-modified LaFeO3 perovskite catalyst (LFC73O) was developed for peracetic acid (PAA) activation to degrade sulfamethoxazole (SMX). Results indicated that the constructed heterogeneous system achieved a 99.7% abatement of SMX within 30 min, exhibiting preferable degradation performance. Chemical quenching experiments, probe experiments, and EPR techniques were adopted to elucidate the involved mechanism. It was revealed that the superior synergistic effect of electron transfer and oxygen defects in the LFC73O/PAA system enhanced the oxidation ability of PAA. The Co atoms doped into LaFeO3 as the main active site with the original Fe atoms as an auxiliary site exhibited high activity to mediate PAA activation via the Co(III)/Co(II) cycle, generating carbon-centered radicals (RO·) including CH3C(O)O· and CH3C(O)OO·. The oxygen vacancies induced by cobalt substitution also served as reaction sites, facilitating the dissociation of PAA and production of ROS. Furthermore, the degradation pathways were postulated by DFT calculation and intermediates identification, demonstrating that the electron-rich sites of SMX molecules such as amino group, aromatic ring, and S-N bond, were more susceptible to oxidation by reactive species. This study offers a novel perspective on developing catalysts with the coexistence of multiple active units for PAA activation in environmental remediation.

The crystal structure of entrapped 8-hydroxyquinoline molecules in an interleaved hydrogen-bonded zigzag channel of sulfamethoxazole molecules

The crystal structure of entrapped 8-hydroxyquinoline molecules in an interleaved hydrogen-bonded zigzag channel of sulfamethoxazole molecules

Response Methodology Optimization and Artificial Neural Network Modeling for the Removal of Sulfamethoxazole Using an Ozone-Electrocoagulation Hybrid Process.

Removing antibiotics from water is critical to prevent the emergence and spread of antibiotic resistance, protect ecosystems, and maintain the effectiveness of these vital medications. The combination of ozone and electrocoagulation in wastewater treatment provides enhanced removal of contaminants, improved disinfection efficiency, and increased overall treatment effectiveness. In this work, the removal of sulfamethoxazole (SMX) from an aqueous solution using an ozone-electrocoagulation (O-EC) system was optimized and modeled. The experiments were designed according to the central composite design. The parameters, including current density, reaction time, pH, and ozone dose affecting the SMX removal efficiency of the OEC system, were optimized using a response surface methodology. The results show that the removal process was accurately predicted by the quadric model. The numerical optimization results show that the optimum conditions were a current density of 33.2 A/m2, a time of 37.8 min, pH of 8.4, and an ozone dose of 0.7 g/h. Under these conditions, the removal efficiency reached 99.65%. A three-layer artificial neural network (ANN) with logsig-purelin transfer functions was used to model the removal process. The data predicted by the ANN model matched well to the experimental data. The calculation of the relative importance showed that pH was the most influential factor, followed by current density, ozone dose, and time. The kinetics of the SMX removal process followed the first-order kinetic model with a rate constant of 0.12 (min-1). The removal mechanism involves various processes such as oxidation and reduction on the surface of electrodes, the reaction between ozone and ferrous ions, degradation of SMX molecules, formation of flocs, and adsorption of species on the flocs. The results obtained in this work indicate that the O-EC system is a potential approach for the removal of antibiotics from water.

Boosting peroxymonosulfate activation by iron-based dual active site for efficient sulfamethoxazole degradation: synergism of Fe and N-doped carbon.

Persulfate activation is emerged as an alternative applied in environment remediation, but it is still a great challenge to develop highly active catalysts for efficient degradation of organic pollutants. Herein, a heterogeneous iron-based catalyst with dual-active sites was synthesized by embedding Fe nanoparticles (FeNPs) onto the nitrogen-doped carbon, which was used to activate peroxymonosulfate (PMS) for antibiotics decomposition. The systematic investigation indicated the optimal catalyst exhibited a significant and stable degradation efficiency of sulfamethoxazole (SMX), in which the SMX can be completely removed in 30min even after 5 cycle tests. Such satisfactory performance was mainly attributed to the successful construction of electron-deficient C centers and electron-rich Fe centers via the short C-Fe bonds. These short C-Fe bonds accelerated electrons to shuttle from SMX molecules to electron-rich Fe centers with a low transmission resistance and short transmission distance, enabling Fe (III) to receive electrons to promote the regeneration of Fe (II) for durable and efficient PMS activation during SMX degradation. Meanwhile, the N-doped defects in the carbon also provided reactive bridges that accelerated the electron transfer between FeNPs and PMS, ensuring the synergistic effects toward Fe (II)/Fe (III) cycle to some extent. The quenching tests and electron paramagnetic resonance (EPR) indicated O2·- and 1O2 were the dominant active species during the SMX decomposition. As a result, this work provides an innovative method to construct a high-performance catalyst to active sulfate for organic contaminant degradation.

Orientated construction of visible-light-assisted peroxymonosulfate activation system for antibiotic removal: Significant enhancing effect of Cl.

Antibiotic contaminants can migrate over long distances in the water, thus possibly causing severe detriment to the environment and even potential harm to human health. Heterogeneous activation of peroxymonosulfate (PMS) assisted by visible light is an emerging and promising technology for the purification of such wastewater. This study designed an ultra-efficient and stable PMS activator (FeCN) to restore the typical antibiotic-polluted water under harsh conditions. About 90.94% of sulfamethoxazole (SMX) was degraded in 35min in the constructed FeCN+PMS/vis system, and the reaction rate constant was nearly 50-fold higher than direct photocatalysis. Electron spin resonance, quenching experiments, LC/MS technique, eco-toxicity assessment, and density functional theory validated that the SMX removal was dominated by the attack of h+, •O2- and 1O2 on the active atoms of SMX molecules with high Fukui index, presenting as a simultaneous degradation and detoxification process. Such a visible-light-assisted PMS activation system also had good resistance to the environmental water bodies and a broad spectrum in the degradation of various pollutants. In particular, Cl- (50mM) could significantly accelerate the removal of SMX with a 32.6-fold increase in catalytic activity, and the mineralization efficiency could reach 56.6% under identical conditions. Moreover, this Cl- containing system excluded the degradation products of disinfection by-products, and such a system was also versatile for different contaminants. This work demonstrates the feasibility of the FeCN+PMS/vis system for the remediation of antibiotic-contaminated wastewater in the presence and absence of Cl-, and also highlights their great potential in WWTPs.

Development of attapulgite based catalytic membrane for activation of peroxymonosulfate: A singlet oxygen-dominated catalytic oxidation process for sulfamethoxazole degradation

Antibiotic contamination of aquatic ecosystems has attracted growing concern over the past few years. As a novel and low-cost catalytic membrane, attapulgite-based ceramic membrane (ATPCM) impregnated with Co3O4 (Co-ATPCM) was successfully prepared for the degradation of sulfamethoxazole (SMX) under peroxymonosulfate (PMS) activation. The physical and chemical properties of ATPCM and Co-ATPCM were characterized by SEM-EDS, XRD, XPS, zeta potential, contact angle and the three-point bending test. Co was stably anchored on ATPCM via X-O-Co (X denotes Al, Si or Mg) bonds during the catalytic process, avoiding Co leaching. Approximately 70 % SMX could be removed by the optimized Co-ATPCM in batch experiments over a wide pH range from 4.0 to 10.0. Furthermore, 58 % SMX degradation was observed during filtration experiments with a high water flux of up to 774 L m−2h−1 (LMH). According to the quenching experiment and electron paramagnetic resonance (EPR) spectroscopy, SO4−, OH and 1O2 were involved in the SMX degradation process, while 1O2 played a dominant role. Density functional theory (DFT) calculation successfully predicted that the sits on SMX molecules with high Fukui index were more susceptible to attacks by free radicals, confirmed by liquid chromatography-Quadrupole-time of flight mass spectrometer (LC-MS). Consequently, a possible pathway for the catalytic oxidation process was proposed based on the results of DFT and LC-MS. This study provided a promising strategy using natural magnesium aluminum silicate clay minerals to prepare cost-effective, efficient, and eco-friendly catalytic membranes for wastewater treatment.

Degradation of sulfamethoxazole in microbubble ozonation process: Performance, reaction mechanism and toxicity assessment

Sulfamethoxazole (SMX) as a widely used antibiotic has caused ecological problems in aquatic environment due to high toxicity and poor biodegradability. In this study, the microbubble ozonation (MB/O3) process was applied for SMX removal, compared with common bubble ozonation (CB/O3) process under the same conditions. The results showed that the SMX degradation and mineralization were much more efficient in MB/O3 process than those in CB/O3 process. The enhancement generation of reactive oxygen species (ROS) in MB/O3 process was proven by electron paramagnetic resonance (EPR) detection, including hydroxyl free radicals (OH), superoxide free radicals (O2−), and singlet oxygen (1O2). In addition, it was found that OH and 1O2 contributed 84.82% and 67.74% of SMX removal in MB/O3 and CB/O3 processes, respectively. The preferential reaction sites of SMX were predicted by density functional theory (DFT) calculation in ozonation process. The sulfonamide group, 17(N), 13(C), 15(C), and 9(C) regions were determined as the more active electrophilic reaction sites. More various and complex degradation pathways of SMX in MB/O3 process were proposed according to intermediates detection and DFT calculation, because both active and inactive sites were found to be attacked due to enhanced ROS oxidation. The more difficult destruction of isoxazole ring than benzene ring in SMX molecule was also observed, especially in CB/O3 process. The increased toxicity was observed during SMX degradation in both ozonation processes. The toxicity prediction and assessment of SMX and its degradation intermediates showed that many intermediates were more toxic than SMX, due to hydroxyl group addition on benzene ring or isoxazole ring by hydroxylation reaction probably.

Evaluation of the adsorption of sulfamethoxazole (SMX) within aqueous influents onto customized ordered mesoporous carbon (OMC) adsorbents: Performance and elucidation of key adsorption mechanisms

Antibiotic resistance genes represent treatment challenges for wastewater treatment systems. These resistance genes are a direct outcome of insufficient treatment of antimicrobial substances within wastewater treatment plants. Thus, this research work concentrated on a typical antibiotic sulfamethoxazole (4-amino-N-[5-methyl-3-isoxazolyl]-benzene sulfonamide or SMX). In this study, the effectiveness of SMX adsorption onto ordered mesoporous carbon (OMC) was first systematically evaluated. SEM, TEM, and BET were used to examine the morphology of OMCs, while XPS, FTIR, and Boehm titration were used to determine the functional groups present on OMCs. The specific surface was found to be 1395.31 m2/g for OMC-900. The behavior of adsorbing SMX onto OMCs was evaluated using kinetics and isotherms studies. The influence of solution pH, temperature, coexisting ions, and natural organic matter (NOM) were also evaluated as to their impacts on SMX adsorption. The results revealed that the mesopores in OMC contributed significantly to SMX adsorption capacity. Adsorption achieved equilibrium after 4 h with an adsorption capacity of 334 mg/g. The Pseudo Second Order Kinetic Model provided a good fit for the adsorption kinetic processes of SMX. The Freundlich Isotherm Model, which suggests physical adsorption, provides a better fit for adsorption isotherm data. The adsorption of SMX onto OMC was exothermic and spontaneous, according to thermodynamic analyses. Most importantly, the adsorption mechanisms of SMX onto OMC include hydrogen bonding and electrostatic interaction. Additionally, a key adsorption mechanism was found to be the affinity (π- π interactions) between the aromatic structures of OMC and the benzene ring in SMX molecule. This study reports a thorough understanding of adsorption components and mechanisms involved in the adsorption of SMX onto OMCs and also the regeneration of OMCs after adsorption.

Construction of Ag nanocluster-modified Ag3PO4 containing silver vacancies via in-situ reduction: With enhancing the photocatalytic degradation activity of sulfamethoxazole

Photocatalytic removal of sulfonamide antibiotics is an effective strategy to solve environmental pollution. Ag3PO4 is a promising anode material for photocatalytic material with photocatalytic degradation ability under ultraviolet light or natural light. Unfortunately, due to its instability, Ag+ could be reduced to Ag0 which loaded onto the surface of Ag3PO4 during the photocatalytic process, causing self-photocorrosion and resulting in the reduction of photocatalytic activity and stability. Herein, Ag3PO4 nanoparticles loaded with Ag nanoclusters containing Ag vacancies (Ag/Ag3PO4-VAg) were constructed by an in-situ reduction strategy to achieve effectively photocatalytic degradation behavior. The Ag nanoclusters loaded on the surface of Ag3PO4 can not only effectively inhibit the self-photocorrosion but also affords a localized surface plasmon resonance (LSPR) effect in the photocatalytic process, thus leading to the efficient generation and rapid transfer of photogenerated carriers behavior. In addition, the Ag vacancies in Ag3PO4 are crucial to increasing the adsorption energy of H2O for further enhancing the capture and accumulation of electrons. In detail, according to Zeta potential analysis, the strong adsorption sites of sulfamethoxazole (SMX) molecules are generated at the interface of Ag and Ag3PO4, which promote the activation of SMX molecules. A 100 ml of 20 mg/L SMX could be completely degraded within 15 min with an apparent rate constant (Kapp) of 0.306 min−1, which far exceeds the activity of most of the photocatalysts. This work may provide an attractive strategy to address the activity, stability of Ag3PO4 and and realizing the green remediation of SMX wastewater.

Ultra-adsorption enhancing peroxymonosulfate activation by ultrathin NiAl-layered double hydroxides for efficient degradation of sulfonamide antibiotics

Sulfonamides have attracted special attention due to their widespread use and refractory nature in the aquatic environment. Heterogeneous catalytic peroxymonosulfate (PMS) activation for sulfonamide degradation has been demonstrated to be an encouraging strategy. Herein, ultrathin nickel aluminium layered double hydroxide (U–NiAl-LDH) was employed as an efficient peroxymonosulfate activator. The adsorption kinetics experiment showed that U–NiAl-LDH exhibited a super-adsorption phenomenon for sulfonamide antibiotics, such as sulfamethoxazole (SMX) and sulfachloropyridazine (SCP). U–NiAl-LDH was composed of 6 layers of a NiAl bimetallic layer structure. The degradation performance of organic contaminants via PMS activation was greatly accelerated by decreasing the number of LDH layers. Ni(II) on the surface of U–NiAl-LDH activated PMS to produce surface-bound hydroxyl radicals and sulfate radicals by donating electrons to cleave the O–O bond of PMS. These in-situ generated reactive oxygen species (ROS) on the surface of U–NiAl-LDH could directly attack adjacent adsorbed SMX or SCP molecules, where the migration distance between the ROS and target contaminants was reduced. Consequently, super-adsorption synergistically promoted the degradation efficiency of SMX and SCP, which decreased the demand for PMS. The newly found ultra-adsorption enhancing peroxymonosulfate activation effect was pioneered for the ultrafast elimination of sulfonamide antibiotics in real water. This proposed mechanism provides preliminary guiding significance to design PMS catalysts with dual reaction sites for the treatment of targeted refractory organic contaminant wastewater.

DEGRADATION OF ANTIBIOTIC SULFAMETHOXAZOLE IN AQUEOUS MEDIA BY UVA/TiO2 PURE-BROOKITE PHOTOCATALYSIS

The appearance of antibiotic sulfamethoxazole (SMX) in natural environments poses a potential risk to human health and ecology. Among many developed treatment techniques to remove and degrade SMX from an aqueous environment, photodegradation using the phase-pure TiO2 nanoparticles (NPs) in brookite structure as an active photocatalyst could be considered as a novel and effective strategy. The photocatalytic degradation of SMX in aqueous media followed an apparent first-order kinetics under the simulated UV-A irradiation. The higher the photocatalysts load, the higher photocatalytic efficiency. The SMX photodegradation over brookite nanoparticles depended on the pH of the SMX solution that was related to changes in chemical isomers of SMX molecules in the range of pH values between 2.0 and 10.0. The degradation efficiency was highest at pH 10.0 (up to 88 % after 180 min under UV-A irradiation) when SMX was in anionic form. With real matrices, the presence of metal ions (in mineral water) and fact-finding organic matter (in surface water) had a small effect on photodegradation efficiency due to either the complexation between SMX with metal ions or the inhibition of free radicals. The obtained results confirmed that the nano-sized TiO2 brookite photocatalyst has a high potential for water and wastewater remediation.

In situ scrutinize the adsorption of sulfamethoxazole in water using AFM force spectroscopy: Molecular adhesion force determination and fractionation

The interaction force of a typical antibiotic molecule during adsorption has never been experimentally determined and fractionated, which hindered the evolution of removal strategies. In this study, sulfamethoxazole (SMX) as a typical antibiotic was stably immobilized onto an atomic force microscopy (AFM) tip without affecting original properties. The SMX modified AFM tip visualized the potential adsorption sites on a graphene oxide (GO) nanosheet for the first time by mapping the SMX adhesion force distribution. Moreover, the interaction force of a single SMX molecule to GO was determined at 38.6 pN which was subsequently fractionated into the hydrophobic (17.9 pN) and π-π (160.0 pN) attractions as well as the electrostatic repulsion (− 139.3 pN) at pH: 5.7. As compared with highly-ordered pyrolytic graphite (HOPG), the introduced oxygen containing groups on GO not only reduced the hydrophobic interaction but also generated an opposite electrostatic repulsion force to SMX. This study experimentally and theoretically revealed the adhesion mechanisms of SMX and potentially other sulfonamide antibiotics in molecular level, which may contribute to the study of antibiotic environmental transportation and the development of next-generation antibiotic remediation protocols.

Ag-TiO2 Nanocomposites: Visible Or Solar Light Driven Plasmonic Photocatalysis?

Background: The demand for photocatalytic processes assisted by solar radiation has stimulated the upgrading of established systems, as the semiconductor modification with noble metals. Objective: the synthesis, characterization, and photocatalytic activity evaluation of the Ag-TiO2, against sulfamethoxazole molecule, and investigate the significance of the plasmonic phenomenon in Visible (450 - 1000nm) and UV-Vis (315-800 nm) radiation. Methods: Different nanocomposites Ag/TiO2 ratios were synthesized by the deposition of Ag nanoparticles on the TiO2 surface by in-situ photoreduction, and then calcinated at 400°C for 2 hr. The chemical-physical properties of the materials were examined by UV-Vis Diffuse Reflectance (UV-Vis DR) Scanning Electronic Microscopy (SEM), Transmission Electronic Microscopy (TEM), X-Ray Energy Dispersive Spectroscopy (EDS). The experiments were conducted in a cooled photochemical reactor irradiated by halogen lamp (250W). The degradation of Sulfamethoxazole was monitored by HPLC-DAD. Results: Although the prepared photocatalysts show an intense plasmonic band centered at 500 nm, no photocatalytic activity was observed in the process assisted by artificial visible radiation (λ ≥ 450 nm). In processes assisted by artificial UV-Vis radiation, the photolysis rate of the model compound (sulfamethoxazole) was higher than the photocatalytic rate, and in the absence of UV radiation, all the reactions were inhibited. The positive effect of the presence of silver nanoparticles onto the TiO2 surface was only evidenced in studies involving solar radiation. Conclusion: The results suggest the need for a balance between UV and Vis radiation to activate the nanocomposite and perform the sulfamethoxazole degradation.

Fate of sulfamethoxazole and potential formation of haloacetic acids during chlorine disinfection process in aquaculture water

There exist two common processes in fishery culture, i.e. antibiotic addition to reduce disease in fishery, and chlorination disinfection to inhibit infectious pathogenic microorganisms. However, antibiotic residues might play important reverse side roles for both aquaculture water pollution and potential formation of chlorination side products. Herein, the transformation behaviour, intermediates analyses and conversion pathway of antibiotic sulfamethoxazole (SMX), and potential generation of halogenated acetic acids (HAAs) in the process of chlorination in fishery water were examined, and the results revealed that the decomposing of SMX satisfied a pseudo first-order kinetic equation. Both the addition of available chlorine and high temperature had affirmative influences on the decontamination of SMX and production of HAAs, and the near-neutral pHs promoted the removal of SMX and generation of HAAs. Br− was favorable for the removal of SMX and yields of brominated acetic acids (Br-AAs). Based on the identified intermediate products, the transformation path of SMX in chlorination process was propounded, to wit, the C–S and S–N bonds in the SMX molecules were firstly cracked, and the primeval intermediate groups are then transformed to form chloroanilines, chlorophenols, etc., and subsequently, chlorophenols were chlorinated and ring-opened to generate toxic HAAs. This study might be meaningful to evaluate the effective removal of sulfonamide antibiotic residues and the potential generation of halogenated DBPs (H-DBPs) when chlorinated in aquaculture water.