Photochemical degradation of sulfadiazine, sulfamerazine and sulfamethazine: Relevance of concentration and heterocyclic aromatic groups to degradation kinetics

Sustainable and Rapid Water Purification at the Confined Hydrogel Interface

Emerging organic contaminants in water matrices have challenged ecosystems and human health safety. Persulfate-based advanced oxidation processes (PS-AOPs) have attracted much attention as they address potential water purification challenges. However, overcoming the mass transfer constraint and the catalyst's inherent site agglomeration in the heterogeneous system remains urgent. Herein, the abundant metal-anchored loading (≈6-8 g m-2) of alginate hydrogel membranes coupled with cross-flow mode as an efficient strategy for water purification applications is proposed. The organic flux of the confined hydrogel interfaces sharply enlarges with the reduction of the thickness of the boundary layer via the pressure field. The normalized property of the system displays a remarkable organic (sulfonamides) elimination rate of 4.87 × 104 mg min-1 mol-1. Furthermore, due to the fast reaction time (<1 min), cross-flow mode only reaches a meager energy cost (≈2.21 Wh m-3) under the pressure drive field. It is anticipated that this finding provides insight into the novel design with ultrafast organic removal performance and low techno-economic cost (i.e., energy operation cost, material, and reagent cost) for the field of water purification under various PS-AOPs challenging scenarios.

Aluminium fumarate biological metal-organic framework as an emerging tool for isolation and detection trace amounts of sulfadiazine in food and water samples

Owing to negative impacts of sulfadiazine (SDZ) as an important group of synthetic antibiotics on public health and ecological systems, it has been a serious concern in recent years. In this research, aluminium fumarate biological metal-organic framework (AlFum Bio-MOF) was synthesized and applied as the best option in terms of extraction performance for detection and quantification of SDZ in a variety of samples. The chemical/structural properties of as-prepared AlFum Bio-MOF were confirmed by spectroscopy techniques. The influence of pH, amount of adsorbent, ultrasonic time (adsorption time (and ionic strength as the main variables in the extraction process were optimized and inspected with central composite design (CCD). Linear dynamic range (LDR), the limit of detection (LOD), and precision value (expressed as relative standard deviation (RSD)) in selected conditions were 20-580, 5.67 ng mL-1, and 3.40 % (n = 3), respectively. The developed method was successfully applied for the determination of SDZ in different water and food samples at two spiked levels with recoveries between 84 and 104 %. Practically, the dispersive micro-solid phase extraction (Dμ-SPE) based on AlFum Bio-MOFs as sorbent could be used to quantify SDZ in complex matrices at trace amounts with acceptable recoveries.

Periodic mesoporous organosilicas containing naphthalenediimides as organic sensitizers for sulfadiazine photodegradation

In this work, periodic mesoporous organosilicas (PMO) functionalized with the organic sentisizer naphthalenediimide (NDI) were employed as heterogeneous catalysts for the photodegradation of the antibiotic sulfadiazine (SDZ), taken as a model for contaminants of emerging concern (CECs). The catalysts, designated as PMONDI, were prepared by surfactant-directed co-condensation of the precursor N,N'-bis(3-triethoxysilylpropyl)- 1,4,5,8-naphthalenediimide with tetraethoxysilane. The synthesized PMONDI were characterized using transmission electron microscopy, nitrogen adsorption isotherms and small and large angle x-ray scattering. The performance of PMONDI catalysts in the photodegradation of SDZ was compared to that of TiO₂ nanoparticles impregnated into SBA-15 mesoporous silica (TiO₂/SBA-15), under irradiation with a Hg lamp with a bandpass filter of 320-500 nm. Under optimal conditions, PMONDI degraded 100% of the SDZ in 45 min, while the total degradation of SDZ was achieved only after 150 min with TiO₂/SBA-15. PMONDI also performed better than TiO₂/SBA-15 in reuse tests. The mechanism of photodegradation with PMONDI involves the formation of excited triplet states of NDI (³NDI*) upon irradiation, which can then react with molecular oxygen to form reactive oxygen species, which degrade SDZ. Analysis of the SDZ degradation products indicated two main pathways: (1) hydroxylation of the aniline ring and (2) SO₂ extrusion and rearrangement, followed by oxidation of the aniline ring to nitrobenzene. In conclusion, the great potential of the PMONDI materials as photocatalysts for CECs degradation was demonstrated in this work, encouraging further research on these materials for the degradation of pollutants.

Typical Sulfonamide Antibiotics Removal by Biochar-Amended River Coarse Sand during Groundwater Recharge

The high porosity of medium-coarse sand (MCS) layers in groundwater recharge areas presents a high environmental risk. Sulfamethoxazole (SMX) and trimethoprim (TMP) are two common sulfonamide antibiotics in surface water that have a high propensity to migrate into groundwater. In this study, four biochars were prepared and biochar-amended soil aquifer treatment (SAT) columns were constructed to remove SMX and TMP. Batch experiments demonstrated that the sorption isotherms conformed to the Freundlich model. The maximum adsorptions of biochars prepared at 700 °C were 54.73 and 67.62 mg/g for SMX and 59.3 and 73.38 mg/g for TMP. Electrostatic interaction may be one of the primary mechanisms of adsorption. The column experiments showed that the SMX and TMP removal rate of the biochar-amended SAT was as high as 96%, while that of the MCS SAT was less than 5%. The addition of biochar greatly improved the retention capacity of the pollutants in the MCS layer in the groundwater recharge area and effectively reduced environmental risk.

Degradation of the Selected Antibiotic in an Aqueous Solution by the Fenton Process: Kinetics, Products and Ecotoxicity

Sulfonamides used in veterinary medicine can be degraded via the Fenton processes. In the premise, the process should also remove the antimicrobial activity of wastewater containing antibiotics. The kinetics of sulfathiazole degradation and identification of the degradation products were investigated in the experiments. In addition, their toxicity against Vibrio fischeri, the MARA^® assay, and unselected microorganisms from a wastewater treatment plant and the river was evaluated. It was found that in the Fenton process, the sulfathiazole degradation was described by the following kinetic equation: r₀ = k C_STZ^{-1 or 0} C_Fe(II)³ C_H2O2^{0 or 1} C_TOC^-2, where r₀ is the initial reaction rate, k is the reaction rate constant, C is the concentration of sulfathiazole, Fe(II) ions, hydrogen peroxide and total organic carbon, respectively. The reaction efficiency and the useful pH range (up to pH 5) could be increased by UVa irradiation of the reaction mixture. Eighteen organic degradation products of sulfathiazole were detected and identified, and a possible degradation mechanism was proposed. An increase in the H₂O₂ dose, to obtain a high degree of mineralization of sulfonamide, resulted in an increase in the ecotoxicity of the post-reaction mixture.

Degradation of carbamazepine by high-voltage direct current gas-liquid plasma with the addition of H2O2 and Fe2

Carbamazepine (CBZ) is a typical psychotropic pharmaceutical which is one of the most commonly detected persistent pharmaceuticals in the environment. The degradation of CBZ in the aqueous solution was studied by a direct current (DC) gas-liquid phase discharge plasma combined with different catalysts (H₂O₂ or Fe²⁺) in this study. The concentrations of reactive species (H₂O₂, O₃, and NO₃^-) and •OH radical yield in the liquid were measured during the discharge process. The various parameters that affect the degradation of CBZ, such as discharge powers, initial concentrations, initial pH values, and addition of catalysts, were investigated. The energy efficiency was 25.2 mg·kW^-1·h^-1 at 35.7 W, and the discharge power at 35.7 W was selected to achieve the optimal balance on the degradation effect and energy efficiency. Both acidic and alkaline solution conditions were conducive to promoting the degradation of CBZ. Both H₂O₂ and Fe²⁺ at low concentration (10-100 mg/L of Fe²⁺, 0.05-2.0 mmol/L of H₂O₂) were observed contributing to the improvement of the CBZ degradation rate, while the promotional effect of CBZ degradation was weakened even inhibition would occur at high concentrations (100-200 mg/L of Fe²⁺, 2.0-5.0 mmol/L of H₂O₂). The degradation rate of CBZ was up to 99.1%, and the total organic carbon (TOC) removal efficiency of CBZ was up to 67.1% in the plasma/Fe²⁺ (100 mg/L) system at 48 min, which suggested that high degradation rate and mineralization efficiency on CBZ could be achieved by employing Fe²⁺ as a catalyst. Based on the intermediate products identified by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry (UPLC-MS), the possible degradation pathways were proposed. Finally, the growth inhibition assay with Escherichia coli (E. coli) showed that the toxicity of plasma/Fe²⁺-treated CBZ solution decreased and a relatively low solution toxicity could be achieved. Thus, the plasma/catalyst could be an effective technology for the degradation of pharmaceuticals in aqueous solutions.

Comparison of chemical and biological degradation of sulfonamides: Solving the mystery of sulfonamide transformation

Sulfonamides (SAs) are widespread in aquatic environments and pose serious environmental risks. The removal efficiencies and degradation mechanisms of SAs in both chemical and biological degradation systems were comprehensively reviewed. Density functional theory (DFT) was utilized to decipher the reaction types and reactive sites of both degradation mechanisms at the electron level. In chemical degradation, the rate of the reactive oxidants to degrade SAs follows the order SO₄•^- ≈ •OH > O₃ > ¹O₂ > ClO₂ ≈ Fe(VI) ≈ HOCl > peroxymonosulfate. pH affects the oxidation-reduction potentials of oxidants, the reactivity of SAs, and the intermolecular force between oxidants and SAs, thereby affecting the chemical degradation efficiencies and mechanisms. In biological degradation, oxidoreductase produced by bacteria, fungi, algae, and plants can degrade SAs. The catalytic activity of the enzyme is affected by the enzyme system, reaction conditions, and type of SAs. Despite the different reaction modes and removal efficiencies of SAs in chemical degradation and biological degradation, the transformation pathways and products show commonalities. Modification of the amino (N¹H₂-) moiety and destruction of sulfonamide bridge (-SO₂-N¹¹H-) moiety are the main pathways for both chemical and biological degradation of SAs. Most oxidants or enzymes can react with the N¹H₂- moiety. Reactions of the -SO₂-N¹¹H- moiety are mainly initiated by the cleavage of S-N bonds for five-membered heterocyclic ring-substituted SAs, and by SO₂ extrusion for six-membered heterocyclic ring-substituted SAs. Chlorine substitution and coupling on the N¹H₂- moiety, hydroxylation of the benzene moiety, oxidation of methyl, and isomerization of the R substituents are the transformation pathways unique to chemical degradation. Formylation/acetylation, glycosylation, pterin conjugation, and deamination of the N¹H₂- moiety are the transformation pathways unique to biological degradation. DFT studies revealed the same reaction types and the same reactive sites of SAs in chemical and biological degradation. Electrophiles are mostly prone to attack the N¹ atom on the amino moiety of neutral SAs and the N¹¹ atom on the sulfonamide bridge moiety of anionic SAs, leading to nitration or electrophilic substitution of the amino moiety and the cleavage of S-N bonds or SO₂ extrusion of the sulfonamide bridge moiety. Reactions on the -SO₂-N¹¹H- moiety eliminate antibacterial activity in the SA degradation process. This review elucidated SA transformation by comparing the chemical and biological degradation of SAs. This could provide theoretical guidance for the development of more efficient and economical treatment technologies for SAs.

Functionalized mesoporous silicas SBA-15 for heterogeneous photocatalysis towards CECs removal from secondary urban wastewater

The photocatalytic activity of TiO₂ nanoparticles (NPs) supported on mesoporous silica SBA-15 (TiO₂/SBA-15) was evaluated for the photodegradation of sulfadiazine (SDZ), as target contaminant of emerging concern (CEC), using either pure water solutions (PW) or a real secondary urban wastewater (UWW) spiked with SDZ. For this purpose, TiO₂/SBA-15 samples with 10, 20 and 30% TiO₂ (w/w) were prepared by the sol-gel post synthetic method on pre-formed SBA-15, using titanium (IV) isopropoxide as a precursor. The TiO₂/SBA-15 materials were characterized by HRTEM, SAXS and XRD, nitrogen adsorption isotherms and UV-vis diffuse reflectance spectroscopy. TiO₂ NPs were shown to be attached onto the external surface, decorating the SBA-15 particles. The TiO₂/SBA-15 catalysts were active in SDZ photodegradation using the annular FluHelik photoreactor, when irradiated with UVA light. The 30% TiO₂/SBA-15 sample presented the best performance in optimization tests performed using PW, and it was further used for the tests with UWW. The photocatalytic activity of 30% TiO₂/SBA-15 was higher (56% SDZ degradation) than that of standard TiO₂-P25 (32% SDZ degradation) in the removal of SDZ spiked in the UWW ([SDZ] = 2 mg L^-1). The photodegradation of SDZ with 30% TiO₂/SBA-15 eached 90% for UWW spiked with a lower SDZ concentration ([SDZ] = 40 μg L^-1). Aside of SDZ, a suit of 65 other CECs were also identified in the UWW sample using LC-MS spectrometry. A fast-screening test showed the heterogeneous photocatalytic system was able to remove most of the detected CECs from UWW, by either adsorption and/or photocatalysis.

Degradation of sulfamerazine by a novel CuxO@C composite derived from Cu-MOFs under air aeration

Most metal-organic frameworks (MOFs) are synthesized from carboxylate and metal precursors by hydrothermal process, which will consume a large amount of solvent and carboxylate. To address this issue, a new strategy for Cu-based MOFs was developed, in which the Cu-based MOFs was obtained by using abundant natural polymer (tannic acid) as one of the precursors and using high-energy ball milling to achieve a self-assembly of tannic acid and copper sulfate. Based on this strategy, a novel Cu-based MOFs derivative (Cu_xO@C composite) was synthesized by high-temperature sintering of Cu-based MOFs and used for sulfamerazine (SMR) removal via O₂ activation. The BET specific surface area and average pore size of Cu_xO@C composite were 110.34 m² g^-1 and 21.06 nm, respectively, which made Cu_xO@C composite had the maximum adsorption capacity (Q_max) for SMR of 104.65 mg g^-1 and favored the subsequent degradation of SMR. The results from XRD and XPS indicated that Cu_xO@C composite contained a lot of Cu⁰ and Cu₂O with the sizes of 76.6 nm and 9.8 nm, respectively, which led to its high performance of O₂ activation. The removal efficiency of SMR and 90.2% TOC achieved 100% and 90.2%, respectively in the Cu_xO@C/air system at initial pH of 4.0, air flow rate of 100 mL min^-1, Cu_xO@C dosage of 1 g L^-1 and reaction time of 30 min. Reactive species, including H₂O₂, OH and O₂^- radicals were detected in the Cu_xO@C/air system, and OH and O₂^- were mainly responsible for the degradation of SMR.

Mineralization of sulfonamides from wastewater using ozone-based systems

Ozone, UV/ozone, ozone/persulfate (PS) and UV/ozone/PS systems were used to mineralize sulfonamides. Sulfadiazine (SDZ), sulfamerazine (SMR) and sulfamethazine (SMZ) were the target compounds. The novel contribution of this study is its determination of the effects of PS addition, sulfonamide structure, pH and salinity on sulfonamide mineralization in ozone-based systems. The mineralization rate of sulfonamides satisfied pseudo-first-order kinetics. The SMZ mineralization rate constant in ozone, UV/ozone, ozone/PS and UV/ozone/PS systems at pH 5 were 0.0058; 0.0101; 0.0069 and 0.0802 min^-1, respectively, and those at pH 7 were 0.0075; 0.0116; 0.0083 and 0.0873 min^-1, respectively. The increase in the number of methyl substituents in the heterocyclic group of SMZ and the corresponding increase in the steric hindrance of radical addition, reduced mineralization rates below those of SMR and SDZ. The addition of PS promoted sulfonamide mineralization in the ozone-based systems; conversely, salinity inhibited sulfonamide mineralization.

Sulfadiazine removal using green zero-valent iron nanoparticles: A low-cost and eco-friendly alternative technology for water remediation

In this work, the effectiveness of green zero-valent iron nanoparticles (gnZVIs) for the removal of the antibiotic sulfadiazine (SDZ) from water via adsorption and reduction was tested. Additionally, the effectiveness of this material as a catalyst for the Fenton and photo-Fenton processes was also investigated. This represents the first study concerning the use of gnZVIs for the degradation of a sulfonamide antibiotic. The results obtained indicate that gnZVIs were able to remove up to 58% of SDZ via adsorption and up to 69% via adsorption plus reduction using a SDZ/Fe³⁺ molar ratio of 1:61.6. Furthermore, gnZVIs showed strong effectiveness as a catalyst for the Fenton and photo-Fenton reactions, with complete SDZ removal in 8 h and 5 min, respectively, using a SDZ/Fe³⁺/H₂O₂ molar ratio of 1:38.4:38.4. These results demonstrate that the use of gnZVIs constitutes an attractive and potential alternative technology for water remediation, reducing environmental impact and operational costs.

Enhanced Fenton-like degradation of sulfadiazine by single atom iron materials fixed on nitrogen-doped porous carbon

The use of single-atom iron catalysts in heterogeneous Fenton-like reactions has demonstrated tremendous potential for antibiotic wastewater treatment. In this study, single-atom iron fixed on nitrogen-doped porous carbon materials (Fe-ISAs@CN) was synthesised using a metal organic framework (MOF) as a precursor. Fe-ISAs@CN was applied as a heterogeneous Fenton catalyst to activate H₂O₂ for the degradation of sulfadiazine (SDZ) in an aqueous solution. The physical and chemical properties of Fe-ISAs@CN were characterised by scanning electron microscopy (SEM), transmission electron microscope (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and rotating disk electrode (RDE) measurements. The results of our degradation experiments indicated that Fe-ISAs@CN exhibited remarkable activity and stability for the degradation of SDZ over a wide pH range; even after five cycles, Fe-ISAs@CN retained a high catalytic efficiency (>80%). The 5,5-dimethyl-1-oxaporphyrin-n-oxide (DMPO)-X signal captured by electron paramagnetic resonance (EPR) spectroscopy indicated that a large amount of hydroxyl radicals (OH) was produced in the reaction system. Quench tests indicated that the OH was the main active substance in the degradation of SDZ. The degradation products of the reaction were analysed by High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS), and possible degradation pathways for the SDZ degradation were proposed.

Efficient mineralization of sulfanilamide over oxygen vacancy-rich NiFe-LDH nanosheets array during electro-fenton process

Electrochemical degradation of toxic sulfanilamide with inexpensive approach is in urgent demand due to the harmful effects of sulfanilamide for both humans and aquatic environments. Here, we reported an efficient mineralization of sulfanilamide by using NiFe-layered double hydroxide (NiFe-LDH) nanosheets array with abundant oxygen vacancies that was in situ grown on exfoliated graphene (EG) by a simple hydrothermal treatment at different temperatures. The hydrothermal temperature was carefully analyzed for control synthesis of oxygen vacancy-rich NiFe-LDH/EG nanosheets array (NiFe-LDH/EG-OVr) for sulfanilamide degradation. Owing to the abundant oxygen vacancies, NiFe-LDH/EG-OVr rapidly generated hydrogen peroxide (H₂O₂) and hydroxyl radical (•OH) during electro-Fenton (EF) process_, which resulted in the 98% mineralization of sulfanilamide in first 80 min. The radicals trapping experiments revealed that the •OH radicals was participated as the main active oxidation species in the efficient mineralization of sulfanilamide. The present results indicated that the oxidative attack by •OH radicals initiated the degradation process of sulfanilamide. During the total degradation of sulfanilamide, several organic compounds including aminophenol, hydroquinone, and oxalic acid, were identified as main intermediates by using gas chromatography-mass spectroscopy (GC-MS) and high-performance liquid chromatography-mass spectroscopy (HPLC-MS).

Sulfaquinoxaline Oxidation and Toxicity Reduction by Photo-Fenton Process

Sulfaquinoxaline (SQX) has been detected in environmental water samples, where its side effects are still unknown. To the best of our knowledge, its oxidation by Fenton and photo-Fenton processes has not been previously reported. In this study, SQX oxidation, mineralization, and toxicity (Escherichia coli and Staphylococcus aureus bacteria) were evaluated at two different setups: laboratory bench (2 L) and pilot plant (15 L). The experimental design was used to assess the influence of the presence or absence of radiation source, as well as different H2O2 concentrations (94.1 to 261.9 mg L-1). The experimental conditions of both setups were: SQX = 25 mg L-1, Fe(II) = 10 mg L-1, pH 2.8 ± 0.1. Fenton and photo-Fenton were suitable for SQX oxidation and experiments resulted in higher SQX mineralization than reported in the literature. For both setups, the best process was the photo-Fenton (178.0 mg L-1 H2O2), for which over 90% of SQX was removed, over 50% mineralization, and bacterial growth inhibition less than 13%. In both set-ups, the presence or absence of radiation was equally important for sulfaquinoxaline oxidation; however, the degradation rates at the pilot plant were between two to four times higher than the obtained at the laboratory bench.

Tetracycline and Sulfonamide Antibiotics in Soils: Presence, Fate and Environmental Risks

Veterinary antibiotics are widely used worldwide to treat and prevent infectious diseases, as well as (in countries where allowed) to promote growth and improve feeding efficiency of food-producing animals in livestock activities. Among the different antibiotic classes, tetracyclines and sulfonamides are two of the most used for veterinary proposals. Due to the fact that these compounds are poorly absorbed in the gut of animals, a significant proportion (up to ~90%) of them are excreted unchanged, thus reaching the environment mainly through the application of manures and slurries as fertilizers in agricultural fields. Once in the soil, antibiotics are subjected to a series of physicochemical and biological processes, which depend both on the antibiotic nature and soil characteristics. Adsorption/desorption to soil particles and degradation are the main processes that will affect the persistence, bioavailability, and environmental fate of these pollutants, thus determining their potential impacts and risks on human and ecological health. Taking all this into account, a literature review was conducted in order to shed light on the current knowledge about the occurrence of tetracycline and sulfonamide antibiotics in manures/slurries and agricultural soils, as well as on their fate in the environment. For that, the adsorption/desorption and the degradation (both abiotic and biotic) processes of these pollutants in soils were deeply discussed. Finally, the potential risks of deleterious effects on human and ecological health associated with the presence of these antibiotic residues were assessed. This review contributes to a deeper understanding of the lifecycle of tetracycline and sulfonamide antibiotics in the environment, thus facilitating decision-making for the application of preventive and mitigation measures to reduce its negative impacts and risks to public health.

Removal of sulfadiazine from simulated industrial wastewater by a membrane bioreactor and ozonation

Ozonation can be used as a polishing treatment for degrading low-concentration pharmaceutical compounds recalcitrant to biological treatment, when large amounts of biodegradable organics have been previously removed by biological processes. Nevertheless, a systematic investigation has not yet been carried out for the coupled MBR + O₃ process through an experimental design approach. Thereby, the purpose of this study is to evaluate the performance of different processes (membrane bioreactor-MBR, ozonation; and integrated MBR + O₃) for removing the antibiotic sulfadiazine (SDZ) from a synthetic wastewater matrix of industrial interest. The MBR behavior was monitored over seven months for different parameters (pH, temperature, permeate flow, transmembrane pressure, biological oxygen demand-BOD₅, chemical oxygen demand-COD, total organic carbon-TOC, solids, and SDZ concentration). Additionally, the amount of SDZ sorbed onto the sludge was characterized, an issue which is scarcely addressed in most research works. Ozonation experiments were conducted in batch mode in a 2-L glass reactor provided with openings for gas flow. For the MBR + O₃ process, the effects of gas flow rate (0.1-1.5 L min^-1) and inlet ozone concentration (4-12 mg L^-1) on SDZ removal from the MBR permeate were systematically assessed using a Doehlert experimental design and response surface methodology. The results indicated that the MBR system showed good performance regarding organic matter removal efficiency, evaluated in terms of BOD₅ (91.5%), COD (93.1%) and TOC (96.3%). In contrast, SDZ was partially removed (33%) by the MBR; in that case, the results indicated that the antibiotic was moderately removed with the sludge and partially biodegraded. In turn, the MBR + O₃ system showed excellent performance for removing SDZ (100%), TOC (97%), BOD₅ (94%) and COD (97%). The statistical analysis confirmed that the influence of ozone gas flow rate upon the SDZ removal rate was more important than that exhibited by inlet ozone concentration. Therefore, coupling MBR and ozone can be considered a promising alternative for point source treatment of antibiotic production wastewater.

Photodegradation of sulfadiazine in different aquatic environments - Evaluation of influencing factors

The presence of antibiotics, such as sulfadiazine (SDZ), in the aquatic environment contributes to the generation of antimicrobial resistance, which is a matter of great concern. Photolysis is known to be a major degradation pathway for SDZ in surface waters. Therefore, influencing factors affecting SDZ photodegradation in different aquatic environments were here evaluated in order to have a better knowledge about its persistence in the environment. Photodegradation of SDZ was found to be more efficient at higher pH (t_1/2 = 6.76 h, at pH = 7.3; t_1/2 = 12.2 h, at pH = 6.3), in the presence of humic substances (HS) (t_1/2 between 1.76 and 2.42 h), as well as in the presence of NaCl (t_1/2 = 1.00 h) or synthetic sea salts (t_1/2 = 0.78 h). Using ˙OH and ¹O₂ scavengers, it was possible to infer that direct photolysis was the main pathway for SDZ photodegradation in ultrapure water. Furthermore, results under N₂ purging confirmed that ¹O₂ was not relevant in the phototransformation of SDZ. Then, the referred observations were used for the interpretation of results obtained in environmental matrices, namely the final effluent of a sewage treatment plant (STPF), fresh and brackish water (t_1/2 between 2.3 and 3.48 h), in which SDZ photodegradation was found to be much faster than in ultrapure water (t_1/2 = 6.76 h).

Porous visible light-responsive Fe3+-doped carbon nitride for efficient degradation of sulfadiazine

The development of efficient solar driven catalyst for the degradation of antibiotics has become increasingly important in environmental protection. However, the reported efficient photocatalysts for antibiotic degradation are limited. In this work, porous Fe³⁺-doped graphitic carbon nitride (g-C₃N₄) with outstanding photocatalytic ability is synthesized and then used as the photocatalyst for the efficient degradation of sulfadiazine (SDZ) under visible light. A series of characterization results indicate that Fe³⁺ is successfully doped into the interlayer of g-C₃N₄ and is stabilized in g-C₃N₄ by Fe-N coordination bond. The SEM, DRS and ESI and transient photocurrent results demonstrated that Fe³⁺-doped g-C₃N₄ has a porous structure, a low band gap, improved separation efficiency of photogenerated electron and holes as well as a wider light absorption range. Such improved physical and chemical properties greatly enhanced the photocatalytic ability. Using Fe³⁺-doped g-C₃N₄ for photocatalytic degradation of SDZ under white light, almost complete degradation of SDZ was achieved with a degradation efficiency as high as 99.8% (whereas only 52.1% for bulk g-C₃N₄) within 90 min. The degradation was mainly ascribe to ¹O₂ during the irradiation, and also a small amount of •O₂^-, OH• and h⁺ are involved in the degradation process. The Fe³⁺-doped g-C₃N₄ was applicable for the degradation of a wide range of antibiotic pollutants.

Sulfonamides-induced oxidative stress in freshwater microalga Chlorella vulgaris: Evaluation of growth, photosynthesis, antioxidants, ultrastructure, and nucleic acids

Sulfadiazine (SD), sulfamerazine (SM1), and sulfamethazine (SM2) are widely used and disorderly discharged into surface water, causing contamination of lakes and rivers. However, microalgae are regard as a potential resource to alleviate and degrade antibiotic pollution. The physiological changes of Chlorella vulgaris in the presence of three sulfonamides (SAs) with varying numbers of –CH₃ groups and its SA-removal efficiency were investigated following a 7-day exposure experiment. Our results showed that the growth inhibitory effect of SD (7.9–22.6%), SM1 (7.2–45.9%), and SM2 (10.3–44%) resulted in increased proteins and decreased soluble sugars. Oxidative stress caused an increase in superoxide dismutase and glutathione reductase levels but decreased catalase level. The antioxidant responses were insufficient to cope-up with reactive oxygen species (hydrogen peroxide and superoxide anion) levels and prevent oxidative damage (malondialdehyde level). The ultrastructure and DNA of SA-treated algal cells were affected, as evident from the considerable changes in the cell wall, chloroplast, and mitochondrion, and DNA migration. C. vulgaris-mediated was able to remove up to 29% of SD, 16% of SM1, and 15% of SM2. Our results suggest that certain concentrations of specific antibiotics may induce algal growth, and algal-mediated biodegradation process can accelerate the removal of antibiotic contamination.

Oxidation of sulfonamides by ferrate(VI): Reaction kinetics, transformation byproducts and toxicity assesment

This study was aimed at the degradation of sulfonamides (SNs) via oxidation with Fe(VI). The reaction kinetics, identification of degradation byproducts and their toxicity were investigated. The pH solution and Fe(VI) loading had significant effects on the degradation of the sulfonamides. The maximum degradation rate occurred at pH 3.0 with a 6:1 ratio Fe(VI): sulfonamide, obtaining 100% degradation of 15 mg L^-1 SN within 5 min. Although Fe(VI) also showed an appreciable reactivity towards SNs (k_app = 9.85-19.63 × 10² M^-1 s^-1) at pH 7. The influence of solution pH on the values of k_app can be explained considering the specific reaction between Fe(VI) and SNs. Degradation rates are also influenced by the presence of inorganic ions in different water matrixes. For this reason, ions present in groundwater enhanced the SNs degradation through a synergistic effect among carbonates, sulfates and Fe(VI). Degradation byproducts identified, through UPLC analysis, allowed us to proposed three degradation pathways depending on pH. At acid pH there is a cleavage of C-S and S-N bonds. At neutral pH nitroso and nitro-derivates are formed. At basic pH hydroxylation is the main reaction. The cytotoxicity assay of HEK-293 and J774 cell lines exposed to Fe(VI) indicated that transformation byproducts had a lower toxicity than SNs as baseline products. Accordingly, this research suggests that Fe(VI) can act as a chemical oxidant to remove SNs antibiotics and it can be used to treat antibiotic pollution in wastewater.

A novel discovery of a heterogeneous Fenton-like system based on natural siderite: A wide range of pH values from 3 to 9

Natural iron-bearing minerals have been proven to be effective for activating H₂O₂ to produce OH, which can be used to degrade organic pollutants. In this study, the performance of siderite to degrade sodium sulfadiazine via catalytic H₂O₂ degradation was investigated at different solution pH values from 3 to 9. An interesting discovery was made: the performance of the siderite-H₂O₂ system was excellent under acidic, neutral, and even alkaline conditions. The influence of various factors (e.g. initial concentration, anions, natural organic matters, etc.) on the system under different pH conditions was investigated, which confirmed that siderite exhibited an excellent catalytic performance. By combining EPR characterization with scavenger research, it was proposed that dissolved iron (Fe²⁺) mainly initiated the homogenous Fenton reaction to degrade pollutants under acidic conditions, while structural Fe²⁺ species present in siderite triggered Fenton-like reactions under neutral or even alkaline conditions. From the SEM and XPS characterizations, oxidation and dissolution of Fe²⁺ on the surface were also observed, confirming our inference concerning the different reaction mechanisms. The experimental findings show that this siderite-H₂O₂ system can be used in solutions with pH values from 3 to 9 and that siderite plays a positive role in soil and groundwater remediation when H₂O₂ is used as an oxidant.

Mechanistic Study on the Role of Soluble Microbial Products in Sulfate Radical-Mediated Degradation of Pharmaceuticals

The role of soluble microbial products (SMP), the most important component of effluent organic matter from municipal wastewater treatment plants, in sulfate radical (SO₄^•-)-based advanced oxidation technologies (AOTs) remains substantially unclear. In this study, we first utilized a suite of macro- and microanalytical techniques to characterize the SMP from a membrane bioreactor for its fundamental molecular, spectroscopic, and reactivity properties. The degradation kinetics of three representative pharmaceuticals (i.e., naproxen, gemfibrozil, and sulfadiazine) in the presence of SMP was significantly reduced as compared to in its absence. Possible mechanisms for the interference by SMP in degrading these target compounds (TCs) were investigated. The low percentage of bound TCs to SMP ruled out the cage effect. The measurement of steady-state ¹O₂ concentration indicated that formation of ¹O₂ upon UV irradiation on SMP was not primarily responsible for the degradation of TCs. However, the comparative and quenching results reveal that SMP absorbs UV light acting as an inner filter toward the TCs, and meanwhile scavenges SO₄^•- with a high second-order rate constant of 2.48 × 10⁸ M_C^-1 s^-1.

Degradation of sulfadiazine, sulfachloropyridazine and sulfamethazine in aqueous media

Antibiotics discharged to the environment constitute a main concern for which different treatment alternatives are being studied, some of them based on antibiotics removal or inactivation using by-products with adsorbent capacity, or which can act as catalyst for photo-degradation. But a preliminary step is to determine the general characteristics and magnitude of the degradation process effectively acting on antibiotics. A specific case is that of sulfonamides (SAs), one of the antibiotic groups most widely used in veterinary medicine, and which are considered the most mobile antibiotics, causing that they are frequently detected in both surface- and ground-waters, facilitating their entry in the food chain and causing public health hazards. In this work we investigated abiotic and biotic degradation of three sulfonamides (sulfadiazine -SDZ-, sulfachloropyridazine -SCP-, and sulfamethazine -SMT-) in aqueous media. The results indicated that, in filtered milliQ water and under simulated sunlight, the degradation sequence was: SCP > SDZ ≈ SMT. Furthermore, the rate of degradation clearly increased with the raise of pH: at pH 4.0, half-lives were 1.2, 70.5 and 84.4 h for SCP, SDZ and SMT, respectively, while at pH 7.2 they were 2.3, 9.4 and 13.2 h for SCP, SMT and SDZ. The addition of a culture medium hardly caused any change in degradation rates as compared to experiments performed in milliQ water at the same pH value (7.2), suggesting that in this case sulfonamides degradation rate was not affected by the presence of some chemical elements and compounds, such as sodium, chloride and phosphate. However, the addition of bacterial suspensions extracted from a soil and from poultry manure increased the rate of degradation of these antibiotics. This increase in degradation cannot be attributed to biodegradation, since there was no degradation in the dark during the time of the experiment (72 h). This indicates that photo-degradation constitutes the main removal mechanism for SAs in aqueous media, a mechanism that in this case was favored by humic acids supplied with the extracts from soil and manure. The overall results could contribute to the understanding of the environmental fate of the three sulfonamides studied, aiding to program actions that could favor their inactivation, which is especially relevant since its dissemination can involve serious environmental and public health risks.

Synthesis of Novel Periodic Mesoporous Organosilicas Containing 1,4,5,8-Naphthalenediimides within the Pore Walls and Their Reduction To Generate Wall-Embedded Free Radicals

Novel periodic mesoporous organosilicas (PMOs) containing 1,4,5,8-Naphthalenediimide (NDI) chromophores as an integral part of the pore walls were synthesized in acidic conditions, in the presence of inorganic tetraethyl orthosilicate, using triblock copolymer surfactant Pluronic P-123 as a template. The NDI precursor, the bridged silsesquioxane N, N'-bis(3-triethoxysilylpropyl)-1,4,5,8-naphthalenediimide, was synthesized by reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride with excess 3-aminopropyltriethoxysilane. A series of samples containing up to 19% (weight %) of NDI were prepared (the materials were labeled PMONDIs). ¹³C and ²⁹Si solid-state nuclear magnetic resonance revealed that the NDI moiety was intact in the PMONDIs and efficiently grafted to the silica network. Samples with up to 16% NDI load presented an ordered two-dimensional-hexagonal mesoscopic structure, according to small-angle X-ray scattering, transmission electron microscopy, and nitrogen adsorption isotherms. Fluorescence spectra of the PMONDIs showed excimer formation upon excitation, suggesting high flexibility of the organic moieties. Reduction of PMONDIs with aqueous sodium dithionite led to the formation of wall-embedded NDI anion radicals, as observed by the appearance of new visible/near-infrared absorption bands. The PMONDIs were also shown to be efficient photocatalysts in the degradation of sulfadiazine, an antibiotic selected here as a model pollutant, which is usually present in water bodies and wastewater.

Iodine-enhanced ultrasound degradation of sulfamethazine in water

This study investigated sulfamethazine (SMT) ultrasound degradation, enhanced by iodine radicals, generated by potassium iodide (KI) and hydrogen peroxide (H₂O₂) in situ. The results showed that the ultrasound/H₂O₂/KI (US/H₂O₂/KI) combination treatment achieved an 85.10 ± 0.45% SMT removal (%) in 60 min under the following conditions: pH = 3.2, ultrasound power of 195 W, initial SMT concentration of 0.04 mmol·L^-1, H₂O₂ concentration of 120 mmol·L^-1, and KI concentration of 2.4 mmol·L^-1. UV-Vis spectrophotometric monitoring of molecular iodine (I₂) and triiodide (I₃^-) revealed a correlation between the SMT degradation and the iodine change in the solution. Quenching experiments using methanol, t-butanol and thiamazole as radical scavengers indicated that iodine radicals, such as I and I₂^-, were more important than hydroxyl radicals (HO) for SMT degradation. SMT degradation under the US/H₂O₂/KI treatment followed pseudo-first order reaction kinetics. The activation energy (E_a) of SMT degradation was 7.75 ± 0.61 kJ·mol^-1, which suggested the reaction was controlled by the diffusion step. Moreover, TOC removal was monitored, and the obtained results revealed that it was not as effective as SMT degradation under the US/H₂O₂/KI system.

Efficient sonoelectrochemical decomposition of sulfamethoxazole adopting common Pt/graphite electrodes: The mechanism and favorable pathways

In this study, efficient degradation of sulfamethoxazole (SMX) with a high synergy factor of 14.7 was demonstrated in a sonoelectrochemical (US-EC) system adopting common Pt and graphite electrodes. It was found that the US-EC system could work effectively at broad pH range of 3-9, but would achieve good performances with appropriate electrochemical conditions at 20mA/cm² and 0.1M Na₂SO₄. Both OH attacking and the anode oxidation would be responsible for the SMX degradation in the US-EC system, while the multiple promotional roles of US would be played homogenously and heterogeneously. US could not only effectively accelerate the decomposition of cathode-generated H₂O₂ into OH, but also lead to the enhancement in the heterogeneous reactions on the two electrodes, i.e. the cathode generation of H₂O₂ as well as the anode oxidation of SMX and H₂O/OH^-. Besides, the US-EC system would decompose SMX molecule via similar and simple pathways, by using either Na₂SO₄ or NaCl electrolytes. It was interesting to note that the US-EC system could successfully avoid the formation of complex chlorinated byproducts that detected in the referring EC system with NaCl. This finding would make the sonoelectrochemical processes favorable in treating practical wastewaters by alleviating the environmental impact of disinfection byproducts.

Abatement and toxicity reduction of antimicrobials by UV/H2O2 process

Antimicrobials are continuously detected in environmental waters and their removal is important to avoid health and microorganisms damage. In this work, the peroxidation assisted by ultraviolet radiation (UV/H₂O₂) was studied to verify if the process was able to degrade sulfaquinoxaline and ofloxacin antimicrobials and to remove the toxicity and the antimicrobial activity of the solution. This process was effective on degradation of the antimicrobials, despite the antimicrobial activity removal, the toxicity of the solution increased throughout the reaction time.

Photodegradation of sulfadiazine catalyzed by p-benzoquinones and picric acid: application to charge transfer complexes

The photo degradation of sulfadiazine drug was effectively carried out at 256 nm in presence of DDQ and sodium nitrite. This was simply followed by UV-Vis spectroscopy. The effect of some additives such as oxalic acid, and/or hematite nanoparticles was studied.

Hybrid Nanostructures Containing Sulfadiazine Modified Chitosan as Antimicrobial Drug Carriers

Chitosan (CH) nanofibrous structures containing sulfadiazine (SDZ) or sulfadiazine modified chitosan (SCH) in the form of functional nanoparticles attached to nanofibers (hybrid nanostructures) were obtained by mono-axial and coaxial electrospinning. The mono-axial design consisted of a SDZ/CH mixture solution fed through a single nozzle while the coaxial design consisted of SCH and CH solutions separately supplied to the inner and outer nozzle (or in reverse order). The CH ability to form nanofibers assured the formation of a nanofiber mesh, while SDZ and SCH, both in form of suspensions in the electrospun solution, assured the formation of active nanoparticles which remained attached to the CH nanofiber mesh after the electrospinning process. The obtained nanostructures were morphologically characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SDZ release profiles and kinetics were analyzed. The SDZ or SCH nanoparticles loosely attached at the surface of the nanofibers, provide a burst release in the first 20 min, which is important to stop the possible initial infection in a wound, while the SDZ and SCH from the nanoparticles which are better confined (or even encapsulated) into the CH nanofibers would be slowly released with the erosion/disruption of the CH nanofiber mesh.

Catalytic ozonation of sulfamethazine antibiotics using Ce0.1Fe0.9OOH: Catalyst preparation and performance

Iron oxyhydroxides (FeOOH) are common crystalline forms of iron which play an important role in catalysis through a series of reduction-oxidation reactions. In this paper, Ce substituted goethite (Ce0.1Fe0.9OOH) was prepared by isomorphous substitution method, characterized by XRD, SEM, TEM-EDS, FTIR, and used for the catalytic ozonation of sulfamethazine (SMT). The results showed that the catalyst can significantly enhance the mineralization of SMT, and more than 42.1% SMT were mineralized in the presence of the catalyst, which is 1.74 times higher than ozonation alone. Moreover, with addition of catalyst, more ozone was dissolved into solution. The solution pH decreased due to small-molecule organic acids formation. The catalytic activity decreased slightly during the repeated batch experiments, due to the corrosion of the catalyst and the adsorption of the residual intermediates on the catalyst surface.

Physicochemical regeneration of high silica zeolite Y used to clean-up water polluted with sulfonamide antibiotics

High silica zeolite Y has been positively evaluated to clean-up water polluted with sulfonamides, an antibiotic family which is known to be involved in the antibiotic resistance evolution. To define possible strategies for the exhausted zeolite regeneration, the efficacy of some chemico-physical treatments on the zeolite loaded with four different sulfonamides was evaluated. The evolution of photolysis, Fenton-like reaction, thermal treatments, and solvent extractions and the occurrence in the zeolite pores of organic residues eventually entrapped was elucidated by a combined thermogravimetric (TGA-DTA), diffractometric (XRPD), and spectroscopic (FT-IR) approach. The chemical processes were not able to remove the organic guest from zeolite pores and a limited transformation on embedded molecules was observed. On the contrary, both thermal treatment and solvent extraction succeeded in the regeneration of the zeolite loaded from deionized and natural fresh water. The recyclability of regenerated zeolite was evaluated over several adsorption/regeneration cycles, due to the treatment efficacy and its stability as well as the ability to regain the structural features of the unloaded material.

Correlating the chemical and spectroscopic characteristics of natural organic matter with the photodegradation of sulfamerazine

The role of aquatic natural organic matter (NOM) in the removal of contaminants of emerging concern has been widely studied. Sulfamerazine (SMR), a sulfonamide antibiotic detected in aquatic environments, is implicated in environmental toxicity and may contribute to the resistance of bacteria to antibiotics. In aquatic systems sulfonamides may undergo direct photodegradation, and, indirect photodegradation through the generation of reactive species. Because some forms of NOM inhibit the photodegradation there is an increasing interest in correlating the spectroscopic parameters of NOM as potential indicators of its degradation in natural waters. Under the conditions used in this study, SMR hydrolysis was shown to be negligible; however, direct photolysis is a significant in most of the solutions studied. Photodegradation was investigated using standard solutions of NOM: Suwannee River natural organic matter (SRNOM), Suwannee River humic acid (SRHA), Suwannee River fulvic acid (SRFA), and Aldrich humic acid (AHA). The steady-state concentrations and formation rates of the reactive species and the SMR degradation rate constants (k1) were correlated with NOM spectroscopic parameters determined using UV-vis absorption, excitation-emission matrix (EEM) fluorescence spectroscopy, and proton nuclear magnetic resonance ((1)H NMR). SMR degradation rate constants (k1) were correlated with steady-state concentrations of NOM triplet-excited state ([(3)NOM(∗)]ss) and the corresponding formation rates ((3)NOM*) for SRNOM, SRHA, and AHA. The efficiency of SMR degradation was highest in AHA solution and was inhibited in solutions of SRFA. The steady-state concentrations of singlet oxygen ([(1)O2]ss) and the SMR degradation rate constants with singlet oxygen (k1O2) were linearly correlated with the total fluorescence and inversely correlated with the carbohydrate/protein content ((1)H NMR) for all forms of NOM. The total fluorescence and EEMs Peak A were confirmed as indicators of (1)O2 formation. Specific ultraviolet absorbance at 254 nm (SUVA254) and aromaticity showed potential correlations with the steady-state concentrations of hydroxyl radical ([HO]ss) and the corresponding formation rates (HO).

Enhanced Fenton-like degradation of refractory organic compounds by surface complex formation of LaFeO(3) and H(2)O(2)

Nanoscale LaFeO(3) was prepared via sol-gel method and characterized by XRD, FTIR and N2 adsorption/desorption experiment. The results indicated that, LaFeO(3) had a typical perovskite structure with a BET area of 8.5m(2)/g. LaFeO(3) exhibited excellent Fenton activity and stability for the degradation of pharmaceuticals and herbicides in water, as demonstrated with sulfamethoxazole, phenazone, phenytoin, acyclovir and 2,4-dichlorophenoxyacetic acid, 2-chlorophenol. Among them, sulfamethoxazole (SMX) could be completely removed in LaFeO(3)-H(2)O(2) system after reaction for 120 min at neutral pH. Based on the ATR-FTIR analysis, the surface complex of LaFeO(3) and H(2)O(2). was formed, which was important and essential for the enhanced Fenton reaction by accelerating the cycle of Fe(3+)/Fe(2+). Hence, more OH and O(2)(-)/HO(2)(-) were then produced in LaFeO(3)-H(2)O(2) system, resulting in more efficient removal of refractory organic compounds. Based on the surface interaction of LaFeO(3) and H(2)O(2), a heterogeneous Fenton reaction mechanism was proposed.

Carbon Stable Isotope Fractionation of Sulfamethoxazole during Biodegradation by Microbacterium sp. Strain BR1 and upon Direct Photolysis

Carbon isotope fractionation of sulfamethoxazole (SMX) during biodegradation by Microbacterium sp. strain BR1 (ipso-hydroxylation) and upon direct photolysis was investigated. Carbon isotope signatures (δ(13)C) of SMX were measured by LC-IRMS (liquid chromatography coupled to isotope ratio mass spectrometry). A new LC-IRMS method for the SMX metabolite, 3-amino-5-methylisoxazole (3A5MI), was established. Carbon isotope enrichment factors for SMX (ε(C)) were -0.6 ± 0.1‰ for biodegradation and -2.0 ± 0.1‰ and -3.0 ± 0.2‰ for direct photolysis, at pH 7.4 and pH 5, respectively. The corresponding apparent kinetic isotope effects (AKIE) for ipso-hydroxylation were 1.006 ± 0.001; these fall in the same range as AKIE in previously studied hydroxylation reactions. The differences in SMX and 3A5MI fractionation upon biotic and abiotic degradation suggest that compound specific stable isotope analysis (CSIA) is a suitable method to distinguish SMX reaction pathways. In addition, the study revealed that the extent of isotope fractionation during SMX photolytic cleavage is pH-dependent.

Photodegradation of sulfonamide antimicrobial compounds (sulfadiazine, sulfamethizole, sulfamethoxazole and sulfathiazole) in various UV/oxidant systems

This study used Na₂S₂O₈, NaBrO8 and H₂O₂to degrade sulfadiazine (SDZ), sulfamethizole (SFZ), sulfamethoxazole (SMX) and sulfathiazole (STZ) under ultraviolet (UV) irradiation. The initial concentration of sulfonamide and oxidant in all experiments was 20 mg/L and 5 mM, respectively. The degradation rate for sulfonamides satisfies pseudo-first-order kinetics in all UV/oxidant systems. The highest degradation rate for SDZ, SFZ, SMX and STZ was in the UV/Na₂S₂O₈, UV/NaBrO₃, UV/Na₂S₂O₈ and UV/H₂O₂ system, respectively. In the UV/Na₂S₂O₈ system, the photodegradation rate of SDZ, SFZ, SMX and STZ was 0.0245 min⁻¹, 0.0096 min⁻¹, 0.0283 min⁻¹ and 0.0141 min⁻¹, respectively; moreover, for the total organic carbon removal rate for SDZ, SFZ, SMX and STZ it was 0.0057 min⁻¹, 0.0081 min⁻¹, 0.0130 min⁻¹ and 0.0106 min⁻¹, respectively. Experimental results indicate that the ability of oxidants to degrade sulfonamide varied with pollutant type. Moreover, UV/Na₂S₂O₈ had the highest mineralization rate for all tested sulfonamides.

Wire-cylinder dielectric barrier discharge induced degradation of aqueous atrazine

The wire-cylinder dielectric barrier discharge reactor was adopted for removal of aqueous atrazine. The effect of different parameters on the degradation efficiency of atrazine was investigated, and the degradation mechanism of atrazine was studied. The experimental results showed that when the discharge power was 50 W and the air flow rate was 140 L h(-1), 93.7% of atrazine was degraded after 18 min of discharge time. The concentrations of generated O3 and H2O2 increased with increasing discharge time. The pH decreased from 6.80 to 2.50, 12.7% of TOC was removed after 18 min. The concentrations of generated Cl(-) and NO3(-) increased significantly during the degradation process of atrazine, and the decreasing toxicity trend was observed for the treated atrazine solution. The degradation byproducts of atrazine were identified using liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS), which might be formed mainly in dechlorination hydroxylation, alkyl oxidation, dechlorination hydroxylation combined with alkyl oxidation and demethylation oxidation reactions.