Degradation of sulfamethoxazole by ozonation combined with ionizing radiation

Iron coagulant regulating reactive species in ionizing radiation process for enhanced degradation of bisphenol A

In the treatment of industrial wastewater by electron beam technology, the flocculation process was frequently coupled with electron beam radiation to improve the water quality to meet the discharge standard. Iron-containing coagulant was widely used in the flocculation process. Therefore, this study investigated the impact of residual iron-containing coagulants on pollutant degradation by the ionizing radiation process. Results showed that the absorbed dose required for complete removal of 50 mg/L bisphenol A decreased from 5 kGy to 2.5 kGy in the presence of 100 μM typical iron coagulant (FeCl3). BPA degradation efficiency increased with the increase of FeCl3 dosage over a wide pH range (3.0-10.0), and the TOC removal efficiency increased from 20% to 45% with the addition of 300 μM Fe(III). The mechanistic investigation demonstrated that •OH was the primary reactive species responsible for BPA degradation. The residual iron coagulants (FeCl3) significantly enhanced the degradation and mineralization efficiency. Under suitable pH conditions (3.0-6.0), the reducing reactive species (eaq‒ and •H) could effectively reduce Fe(III) to Fe(II), which then reacted with H2O2, thus inducing in-situ Fenton reaction to generate more •OH, thus promoting the radiolysis degradation of micropollutants. This study explored the potential of using residual iron coagulants from the flocculation process to enhance the performance of electron beam technology for wastewater treatment.

Regulation of reactive species during ionizing radiation by peroxydisulfate for enhanced degradation of typical pollutants in coking wastewater

This study focused on exploring the effect of peroxydisulfate (PDS) on the regulation of reactive species during water radiolysis process and its potential application for degrading organic pollutants. The results indicated that PDS was successfully activated by ionizing radiation for efficient removal of three typical phenolic compounds over a wide pH range (3.0∼12.0) at absorbed dose of 5 kGy. Chemical probe methods provided the evidence that the addition of PDS could introduce the sulfate radicals (SO4•-) and enhance the production of hydroxyl radicals (•OH). According to the quenching tests, •OH and SO4•- were the dominant reactive species responsible for the degradation of 4-NP, while hydrated electron (eaq-) played a minor role. The regulatory effect of PDS on active species in the ionizing radiation process could divided by (i) PDS could be directly activated by ionizing radiation to produce •OH and SO4•- via energy transfer pathway; (ii) PDS could boost the conversion of eaq- to SO4•- via electron transfer pathway. Furthermore, we assessed the applicability of the IR and IR/PDS systems in treating mixed solutions containing various pollutants and actual coking wastewater.

Advanced carbo-catalytic degradation of antibiotics using conductive polymer-seaweed biochar composite: Exploring N/S functionalization and non-radical dynamics

Polyaniline (PANI) and Saccharina Japanica seaweed (kelp) biochar (KBC) composites were synthesized in-situ through polymerization. This study presents a novel approach to the degradation of sulfamethoxazole (SMX), a prevalent antibiotic, using a PANI-KBC composite to activate peroxymonosulfate (PMS). Extensive characterizations of the PANI-KBC composite were conducted, resulting in successful synthesis, uniform distribution of PANI on the biochar surface, and the multifunctional role of PANI-KBC in SMX degradation. A removal efficiency of 97.24% for SMX (10 mg L-1) was attained in 60 min with PANI-KBC (0.1 g L-1) and PMS (1.0 mM) at pH 5.2, with PANI-KBC showing effectiveness (>92%) across a pH range of 3.0-9.0. In the degradation of SMX, both radical (SO4•- and •OH) and non-radical (1O2 and electron transfer) pathways are involved. The reaction processes are critically influenced by the roles of SO4•-, 1O2 and electron transfer mechanisms. It was suggested that pyrrolic N, oxidized sulfur (-C-SO2-C-), structural defects, and O-CO were implicated in the production of 1O2 and electron transfer processes, respectively, and a portion of 1O2 originated from the conversion of O2•-. The study evaluated by-product toxicity, composite reusability, and stability, confirming its practical potential for sustainable groundwater remediation.

Mechanism of adsorption and targeted degradation of antimicrobial micropollutant sulfamethoxazole in aquatic environments

FHWSB as an integrated absorptive catalyst, based on Walnut shell biochar (WSB) via hydrochloric acid modification and ferrous chloride impregnation, was prepared, reacted with H2O2 to generate active free radicals •OH and •O2-, which oxidized and degraded about 80% of micro-pollutant sulfamethoxazole (SMX) from water, effectively resolving micro-pollutants' removal being inefficient because of high toxicity, persistence, and bioaccumulation in existed methods. It was clarified the specific degradation pathways and mechanisms of SMX by FHWSB synergistic H2O2 via characterization and analysis assisted DFT calculations. Furthermore, it was found that the toxicity of a series of intermediates produced by SMX degraded continued to decline, consistent with its direction of degradation via toxicological analysis. The work provides a simple and feasible strategy for the effective removal of antibiotic micro-pollutants in aquatic environments.

Mediated Peroxymonosulfate Activation at the Single Atom Fe-N3O1 Sites: Synergistic Degradation of Antibiotics by Two Non-Radical Pathways

The activation of persulfates to degrade refractory organic pollutants is a hot issue in advanced oxidation right now. Here, it is reported that single-atom Fe-incorporated carbon nitride (Fe-CN-650) can effectively activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) removal. Through some characterization techniques and DFT calculation, it is proved that Fe single atoms in Fe-CN-650 exist mainly in the form of Fe-N3O1 coordination, and Fe-N3O1 exhibited better affinity for PMS than the traditional Fe-N4 structure. The degradation rate constant of SMX in the Fe-CN-650/PMS system reached 0.472 min-1, and 90.80% of SMX can still be effectively degraded within 10 min after five consecutive recovery cycles. The radical quenching experiment and electrochemical analysis confirm that the pollutants are mainly degraded by two non-radical pathways through 1O2 and Fe(IV)═O induced at the Fe-N3O1 sites. In addition, the intermediate products of SMX degradation in the Fe-CN-650/PMS system show toxicity attenuation or non-toxicity. This study offers valuable insights into the design of carbon-based single-atom catalysts and provides a potential remediation technology for the optimum activation of PMS to disintegrate organic pollutants.

Radiolysis performance of ibuprofen using ionizing processes: kinetics and energy consumption

ABSTRACTIonizing technologies are used for disinfection and treatment of different industrial wastewaters. For this purpose, the radiolytic degradation of ibuprofen (IBP), selected within the main detected pharmaceuticals in different water locations with different concentrations, was investigated. Irradiation was performed with a gamma irradiator (60Co) and with electron beam accelerator. The degree of ibuprofen degradation was monitored following the evolution of its absorbance, the residual concentration by HPLC, carbon oxygen demand and total organic carbon. The degradation of IBP was higher than the removal of TOC or COD and reached 95% according to residual concentration. This pollutant (at 0.1 mM) was totally degraded when irradiated at 3 kGy and needed higher doses (7-10 kGy) for the highest concentrations (0.8-1 mM). The addition of 1 mM of persulfate ion remarkably enhanced IBP degradation by around 2 and 2.8 times for 5 and 10 kGy, respectively. Pseudo-first-order reaction kinetics could be used to depict the degradation process of IBP in all conditions. Electrical energy per order (EEO) was estimated under various conditions. The smallest EEO was obtained when gamma radiation and persulfate ion were combined. The possible degradation pathways of IBP were proposed. The results achieved in this study can be used to optimize large-scale application of nuclear techniques in water treatment in particular in treating pharmaceutical effluents.

Sonophotocatalytic degradation of sulfamethoxazole using lanthanum ferrite perovskite oxide anchored on an ultrasonically exfoliated porous graphitic carbon nitride nanosheet

The lanthanum ferrite perovskite (La0.8FO) was synthesized using a citric combustion route and then modified with a porous graphitic nitride nanosheet via the wet impregnation-assisted ultrasonic method to produce La0.8FO@PgNS. Various techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet diffuse reflectance spectroscopy (UV-DRS), and Tauc plot analysis were employed to confirm the functional moieties, crystallinity, phase change, morphology, composition, and bandgap of La.0.8FO and La0.8FO@PgNS. La0.8FO and La0.8FO@PgNS were used for the sonophotocatalytic oxidative degradation of sulfamethoxazole (SMX) under low energy and ultrasound wave frequency in the presence of visible light. La0.8FO and La0.8FO@PgNS exhibited a sonophotocatalytic degradation capacity of 52.06 and 99.60%, respectively. Furthermore, the rate constant at the optimum condition of pH 7 and 5 mg L-1 concentration was 0.01343 and 0.01494 min-1 for La0.8FO and La0.8FO@PgNS, respectively. The integration of sonolysis and photocatalysis in the remediation process of SMX resulted in a synergy of 2.5-fold. Ultrasonic waves and hydroxyl and superoxide radicals are the main species governing the degradation process while La0.8FO@PgNS was stable over 8 cycles, proving to be a sustainable material for environmental remediation.

Facile synthesis of ball-milling and oxalic acid co-modified sludge biochar to efficiently activate peroxymonosulfate for sulfamethoxazole degradation: 1O2 and surface-bound radicals

A novel approach of ball milling and oxalic acid was employed to modify sludge-based biochar (BOSBC) to boost its activation performance for peroxymonosulfate (PMS) towards efficient degradation of sulfamethoxazole (SMX). 98.6% of SMX was eliminated by PMS/BOSBC system within 60 min. Furthermore, PMS/BOSBC system was capable of maintaining high removal rates for SMX (>88.8%) in a wide pH range from 3 to 9, and displayed a high tolerance to background electrolytes including inorganic ions and humic acid (HA). Quenching experiments, electron paramagnetic resonance (EPR) analysis, in-situ Raman characterization and PMS decomposition experiments confirmed that the non-radicals of 1O2 and surface-bound radicals were the main contributors to SMX degradation by PMS/BOSBC system. The results of ecotoxicity assessment illustrated that all transformed products (TPs) generated in PMS/BOSBC system were less toxic than that of SMX. After five reuse cycles, PMS/BOSBC system still maintained a high removal rate for SMX (77.8%). Additionally, PMS/BOSBC system exhibited excellent degradation performance for SMX in various real waters (Yangtze River water (76.5%), lake water (74.1%), tap water (86.5%), and drinking water (98.1%)). Overall, this study provided novel insights on non-metal modification for sludge-based biochar and non-radical mechanism, and offered a feasible approach for municipal sludge disposal.

Application of artificial intelligence for the optimization of advanced oxidation processes to improve the water quality polluted with pharmaceutical compounds

Sulfamethoxazole and metronidazole are emerging pollutants commonly found in surface water and wastewater. These compounds have a significant environmental impact, being necessary in the design of technologies for their removal. Recently, the advanced oxidation process has been proven successful in the elimination of this kind of compounds. In this sense, the present work discusses the application of UV/H2O2 and ozonation for the degradation of both molecules in single and binary systems. Experimental kinetic data from O3 and UV/H2O2 process were adequately described by a first and second kinetic model, respectively. From the ANOVA analysis, it was determined that the most statistically significant variables were the initial concentration of the drugs (0.03 mmol L-1) and the pH = 8 for UV/H2O2 system, and only the pH (optimal value of 6) was significant for degradation with O3. Results showed that both molecules were eliminated with high degradation efficiencies (88-94% for UV/H2O2 and 79-98% for O3) in short reaction times (around 30-90 min). The modeling was performed using a quadratic regression model through response surface methodology representing adequately 90 % of the experimental data. On the other hand, an artificial neural network was used to evaluate a non-linear multi-variable system, a 98% of fit between the model and experimental data was obtained. The identification of degradation byproducts was performed by high-performance liquid chromatography coupled to a time mass detector. After each process, at least four to five stable byproducts were found in the treated water, reducing the mineralization percentage to 20% for both molecules.

Decolorization and degradation of various dyes and dye-containing wastewater treatment by electron beam radiation technology: An overview

The treatment of dye-containing wastewater generated from textile industries is still a challenge, and various technologies, including physical, chemical and biological ones have been used. In recent years, the ionizing radiation (usually including gamma ray generated by radionuclide, such as 60Co and 137Cs, and electron beam generated by electron accelerator) technology has received increasing attention for degrading refractory or toxic organic pollutants in wastewater because of its unique advantages, such as no chemical additives, fast reaction rate, strong degradation capacity, high efficiency, flexibility, controllability. Compared to the conventional wastewater treatment processes, ionizing radiation technology, as a disruptive wastewater treatment technology, is more efficient for the decolorization and degradation of dyes and the treatment of dye-containing wastewater. In this paper, the recent advances in the treatment of dye-containing wastewater by ionizing radiation, in particular by electron beam (EB) radiation were summarized and analyzed, focusing on the decolorization and degradation of various dyes. Firstly, the formation of various reactive species induced by radiation and their interactions with dye molecules, as well as the influencing factors on the removal efficiency of dyes were discussed. Secondly, the researches on the treating dye-containing wastewater by electron beam radiation technology were systematically reviewed. Then, the decolorization and degradation mechanisms by electron beam radiation were further discussed in detail. And the integrated processes that would contribute to the advancement of this technology in practical applications were examined. More importantly, the recent advances of electron beam radiation technology from laboratory to application were reviewed, especially successful operation of dye-containing wastewater treatment facilities in China. And eventually, current challenges, future research directions, and outlooks of electron beam radiation technology were proposed for further advancing this technology for the sustainable development of water resources.

Advanced treatment of coking wastewater: Recent advances and prospects

Advanced treatment of refractory industrial wastewater is still a challenge. Coking wastewater is one of coal chemical wastewater, which contains various refractory organic pollutants. To meet the more and more rigorous discharge standard and increase the reuse ratio of coking wastewater, advanced treatment process must be set for treating the biologically treated coking wastewater. To date, several advanced oxidation processes (AOPs), including Fenton, ozone, persulfate-based oxidation, and iron-carbon micro-electrolysis, have been applied for the advanced treatment of coking wastewater. However, the performance of different advanced treatment processes changed greatly, depending on the components of coking wastewater and the unique characteristics of advanced treatment processes. In this review article, the state-of-the-art advanced treatment process of coking wastewater was systematically summarized and analyzed. Firstly, the major organic pollutants in the secondary effluents of coking wastewater was briefly introduced, to better understand the characteristics of the biologically treated coking wastewater. Then, the performance of various advanced treatment processes, including physiochemical methods, biological methods, advanced oxidation methods and combined methods were discussed for the advanced treatment of coking wastewater in detail. Finally, the conclusions and remarks were provided. This review will be helpful for the proper selection of advanced treatment processes and promote the development of advanced treatment processes for coking wastewater.

Efficient Degradation of Sulfamethoxazole by Diatomite-Supported Hydroxyl-Modified UIO-66 Photocatalyst after Calcination

Sulfamethoxazole (SMX) is a widely used antibiotic to treat bacterial infections prevalent among humans and animals. SMX undergoes several transformation pathways in living organisms and external environments. Therefore, the development of efficient remediation methods for treating SMX and its metabolites is needed. We fabricated a photo-Fenton catalyst using an UIO-66 (Zr) metal-organic framework (MOF) dispersed in diatomite by a single-step solvothermal method for hydroxylation (HO-UIO-66). The HO-UIO-66-0/DE-assisted Fenton-like process degraded SMX with 94.7% efficiency; however, HO-UIO-66 (Zr) is not stable. We improved the stability of the catalyst by introducing a calcination step. The calcination temperature is critical to improving the catalytic efficiency of the composite (for example, designated as HO-UIO-66/DE-300 to denote hydroxylated UIO-66 dispersed in diatomite calcined at 300 °C). The degradation of SMX by HO-UIO-66/DE-300 was 93.8% in 120 min with 4 mmol/L H2O2 at pH 3 under visible light radiation. The O1s XPS signatures signify the stability of the catalyst after repeated use for SMX degradation. The electron spin resonance spectral data suggest the role of h+, •OH, •O2-, and 1O2 in SMX degradation routes. The HO-UIO-66/DE-300-assisted Fenton-like process shows potential in degrading pharmaceutical products present in water and wastewater.

Selective oxidation of organic pollutants based on reactive oxygen species and the molecular structure: Degradation behavior and mechanism analysis

The selective and rapid elimination of refractory organic pollutants from surface water is significant. However, the relationship of between reactive oxygen species (ROSs) and diversified pollutants molecular structures still needs to be further clarified. Here, we utilize polydopamine (PDA)-assisted coating strategy to prepare hollow 2D carbon nanosheet (ZPL-HCNS) and 2D Co3O4 nanosheet (ZPL-Co3O4) by thermolysis of PDA coated ZIF-L (ZIF-L@PDA) precursor under different gas atmosphere, which realizes the controlled generation of radicals and non-radicals. Organic pollutants including bisphenols, sulfonamides, quinolones, tetracyclines, and azo dyes are applied to assess the catalytic performance. Results show that dyes containing azo structure are more likely to be degraded by radical process, which is due to that the energy (ΔE) requirements to break the azo bond is higher than energy released from singlet oxygen to oxygen molecule and lower than that of sulfate radical to sulfate. Frontier molecular orbital theory HOMO-LUMO and Fukui function expounded the possible selectivity mechanism. In addition, the degradation pathway and biotoxicity test are carried out. This work provides a reference to illustrate the selective degradation for ROSs and molecular structure of pollutants.

Two-dimensional manganese-iron bimetallic MOF-74 for electro-Fenton degradation of sulfamethoxazole

This study reported a novel application of Mn_0.67Fe_0.33-MOF-74 with two-dimensional (2D) morphology grown on carbon felt as a cathode for efficiently removing antibiotic sulfamethoxazole in the heterogeneous electro-Fenton system. Characterization demonstrated the successful synthesis of bimetallic MOF-74 by a simple one-step method. Electrochemical detection showed that the second metal addition and morphological change improved the electrochemical activity of the electrode and contributed to pollutant degradation. At pH 3 and 30 mA of current, the degradation efficiency of SMX reached 96% with 12.09 mg L^-1 H₂O₂ and 0.21 mM ·OH detected in the system after 90 min. During the reaction, electron transfer between ≡Fe^II/III and ≡Mn^II/III promoted divalent metal ions regeneration, which ensured the continuation of the Fenton reaction. Two-dimensional structures exposed more active sites favoring ·OH production. The pathway of sulfamethoxazole degradation and the reaction mechanisms were proposed based on the intermediates identification by LC-MS and radical capture results. High degradation rates were still observed in tap and river water, revealing the potential of Mn_0.67Fe_0.33-MOF-74@CF for practical applications. This study provides a simple MOF-based cathode synthesis method, which enhances our understanding of constructing efficient electrocatalytic cathodes based on morphological design and multi-metal strategies.

Detection and removal technologies for ammonium and antibiotics in agricultural wastewater: Recent advances and prospective

With the extensive development of industrial livestock and poultry production, a considerable part of agricultural wastewater containing tremendous ammonium and antibiotics have been indiscriminately released into the aquatic systems, causing serious harms to ecosystem and human health. In this review, ammonium detection technologies, including spectroscopy and fluorescence methods, and sensors were systematically summarized. Antibiotics analysis methodologies were critically reviewed, including chromatographic methods coupled with mass spectrometry, electrochemical sensors, fluorescence sensors, and biosensors. Current progress in remediation methods for ammonium removal were discussed and analyzed, including chemical precipitation, breakpoint chlorination, air stripping, reverse osmosis, adsorption, advanced oxidation processes (AOPs), and biological methods. Antibiotics removal approaches were comprehensively reviewed, including physical, AOPs, and biological processes. Furthermore, the simultaneous removal strategies for ammonium and antibiotics were reviewed and discussed, including physical adsorption processes, AOPs, biological processes. Finally, research gaps and the future perspectives were discussed. Through conducting comprehensive review, future research priorities include: (1) to improve the stabilities and adaptabilities of detection and analysis techniques for ammonium and antibiotics, (2) to develop innovative, efficient, and low cost approaches for simultaneous removal of ammonium and antibiotics, and (3) to explore the underlying mechanisms that governs the simultaneous removal of ammonium and antibiotics. This review could facilitate the evolution of innovative and efficient technologies for ammonium and antibiotics treatment in agricultural wastewater.

Thermal effect on sulfamethoxazole degradation in a trivalent copper involved peroxymonosulfate system

Persulfate (PS) activated by thermal or homogeneous metals can generate reactive oxygen species (ROS) and high-valence-state metals for contaminants degradation, showing great potential for applications. However, thermal effect in peroxymonosulfate (PMS) system with high-valence-state metal is still ambiguous. In this study, divalent copper (Cu(II)) catalysis was taken to explore thermal effect on PMS performance. Results showed that the Sulfamethoxazole (SMX) removal efficiency in the Cu(II)/PMS system at 60 min increased by only 5.9% with temperature increase from 30 °C to 60 °C. Moreover, SMX removal efficiency was excellent at neutral or basic pH, best with PMS concentration of 2.4 mM, and slightly affected by Cu(II) concentration. The singlet oxygen (¹O₂) was identified as main active species at low temperature while sulfate radicals (SO₄^-) was more effective at high temperature with Cu(II) co-activation. Also, trivalent copper (Cu(III)) was an important active species. The higher Cu(III) content, the better SMX removal efficiency, but the stronger intermediates toxicity. In combination with removal efficiency and intermediates toxicity at different temperatures, 30 °C was the optimal reaction temperature. Overall, this study provides new perspective on utilization of waste heat and high-valence-state metal for organic wastewater treatment in PMS systems.

Degradation of dibutyl phthalate by ozonation in the ultrasonic cavitation-rotational flow interaction coupled-field: performance and mechanism

Dibutyl phthalate (DBP) is present in hydraulic fracturing flowback and produced water. Degradation of DBP in aqueous by means of ozonation in ultrasonic cavitation-rotational flow interaction coupled-field (UC-RF coupled-field) was studied. The effect of ozone dosage, ozone intake flow, operating temperature, initial pH, DBP initial concentration, liquid flow rate, and ultrasonic power on the DBP removal was investigated. Results indicated that the DBP degradation rate was strongly influenced by the liquid flow rate and the ultrasonic power over the range investigated. HCO₃^- and Cl^- revealed an inhibitory effect on the DBP removal. SO₄^2- seemed to have no effect on DBP removal. The ozone utilization efficiencies in the UC-RF coupled-field were 2.77 and 1.13 times higher than those in the conventional microporous aeration (CMA) and rotating-flow microbubble aeration (RFMA), respectively. The DBP degradation rate was diminished in the presence of tert-butyl alcohol. Cavitation bubbles are considered as innumerable microreactors. Degradation of DBP by direct ozonation, hydroxyl radical (·OH) oxidation, high pressure, and high-temperature pyrolysis was demonstrated. Finally, a possible degradation pathway of DBP is obtained on the basis of the main reaction intermediates.

Ball milling-assisted preparation of sludge biochar as a novel periodate activator for nonradical degradation of sulfamethoxazole: Insight into the mechanism of enhanced electron transfer

The non-radical pathway of periodate (PI) activation for the removal of persistent organic contaminants has received increasing attention due to its higher stability and oxidative advantages. In this study, the degradation of sulfamethoxazole (SMX) by ball mill treated magnetic sludge biochar (BM-MSBC) through activation of PI by electron transfer mechanism was reported. Experimental and characterization results showed that the ball milling treatment resulted in a better pore and defect structure, which also significantly enhanced the electron transfer capacity of the sludge biochar. The BM-MSBC/PI system exhibited notable dependence of activator concentration and initial pH, while the effect of PI concentration was not significant. The coexisting substances (common anions and natural organic matters) hardly affect the degradation of SMX in the BM-MSBC/PI system. The phytotoxicity experiments suggested that the treatment of BM-MSBC/PI system could significantly reduce the biological toxicity of SMX solution. This study provides a novel, economical, and facile modification method for the application of sludge biochar in advanced oxidation processes.

Converting Hybrid Mechanisms to Electron Transfer Mechanism by Increasing Biochar Pyrolysis Temperature for the Degradation of Sulfamethoxazole in a Sludge Biochar/Periodate System

In this study, sludge biochar was prepared under four pyrolysis temperatures (SBC300, SBC500, SBC700, and SBC900) and then was employed to activate periodate (PI) for the degradation of sulfamethoxazole (SMX). Various characterization methods were employed to investigate the effect of pyrolysis temperature on the physicochemical properties of sludge biochar and the activation capacity of periodate. The SMX adsorption capacity of SBCs and the ability of activating PI to degrade SMX increased with the increasing pyrolysis temperature. The degradation of SMX by the SBCs/PI systems was highly dependent on the initial pH of the solution and the dosage of SBCs. Mechanistic studies indicated that the degradation of SMX by the SBCs/PI system was mainly based on an electron-mediated transfer mechanism. Additionally, the electron transfer capacity of the SBCs affected the defects and the degree of graphitization. The contribution of free radicals to SMX degradation decreases with increasing pyrolysis temperature. Toxicity experiments demonstrated that the toxic elimination of SMX by the SBCs/PI system was enhanced with increasing pyrolysis temperature.

Kinetic and mechanism investigation on the gamma irradiation induced degradation of quizalofop-p-ethyl

An efficient gamma radiolytic decomposition of one of the extensively used herbicides in the world quizalofo-p-ethyl (QPE) was explored under different experimental conditions. Aqueous solutions of QPE were irradiated by gamma rays emitted by a Cobalt 60 source. QPE aqueous solutions were irradiated at doses of 0.5-3 kGy with 26.31 Gy min^-1 dose rate. Obtained results indicated that removal efficiency of 98.5% and 73% of QPE were obtained, respectively, in absence and in presence of dissolved oxygen. Change of absorption spectra, pH effect and Total Organic Carbon (TOC) were carried out and studied. It was found that all absorption bands decreased with increasing irradiation dose and disappear totally after 3 kGy applied dose. Three pH conditions (pH = 10, pH = 6.2 and pH = 3) were applied in radiolytic degradation of QPE showing that the best removal efficiency has been found for neutral pH. Interestingly, the % TOC removal reaches 98% at 3 kGy indicated practically total mineralization. Furthermore, spectrophotometric analyses argued in favour of a pseudo-first-order kinetic of QPE degradation. The resulting apparent rate constant value is approximately k_app = (0.012 ± 0.001) min^-1. Finally, several by-products such as 6-chloroquinoxalin -2-ol, 2-(4-hydroxy-phenyoxy) propionate, 1,4-hydroquinone, quinone, 4-chlorobenzene-1,2diol and 1,2,4-benzenetriol were identified by gas chromatography-mass spectrometry (GC/MS) evidencing that radiation process starting with the fragmentation of the molecule involving the hydroxyl radical, which is generated by the radiolysis of water. Based on the identification intermediates, a degradation mechanistic schema of QPE has been proposed.

Impact of gamma-irradiation on the degradation and mineralization of hydroxychloroquine aqueous solutions

In this work, the effect of gamma irradiation emitted by Cobalt 60 source has been investigated for the degradation of hydroxychloroquine (HCQ). The monitoring of the gamma irradiation treatment of HCQ aqueous solutions was followed by UV-visible, chemical oxygen demand, total organic carbon (TOC) and LC/MS analyses. Effects of several important parameters such as concentration, dose rate and pH on the degradation efficiency were studied then evaluated. Achieved results showed that % TOC removal efficiency of 98.5 was obtained after 8 kGy absorbed dose which warrants HCQ mineralization. The process was found to be more efficient when the initial pollutant concentration was low, with higher dose rate and at neutral pH. Furthermore, HCQ degradation kinetic study revealed a pseudo-first-order kinetic. Additionally, based on by-products identified by LC/MS, a degradation mechanistic schema mediated through hydroxyl radicals generated by water radiolysis has been proposed. Finally, in order to check the potential industrial application viability the energy consuming was evaluated.

In silico toxicity evaluation for transformation products of antimicrobials, from aqueous photolysis degradation

This study investigates degradation processes of three antimicrobials in water (norfloxacin, ciprofloxacin, and sulfamethoxazole) by photolysis, focusing on the prediction of toxicity endpoints via in silico quantitative structure-activity relationship (QSAR) of their transformation products (TPs). Photolysis experiments were conducted in distilled water with individual solutions at 10 mg L^-1 for each compound. Identification of TPs was performed by means of LC-TOF-MS, employing a method based on retention time, exact mass fragmentation pattern, and peak intensity. Ten main compounds were identified for sulfamethoxazole, fifteen for ciprofloxacin, and fifteen for norfloxacin. Out of 40 identified TPs, 6 have not been reported in the literature. Based on new data found in this work, and TPs already reported in the literature, we have proposed degradation pathways for all three antimicrobials, providing reasoning for the identified TPs. QSAR risk assessment was carried out for 74 structures of possible isomers. QSAR predictions showed that all 19 possible structures of sulfamethoxazole TPs are non-mutagenic, whereas 16 are toxicant, 18 carcinogenic, and 14 non-readily biodegradable. For ciprofloxacin, 28 out of the 30 possible structures for the TPs are mutagenic and non-readily biodegradable, and all structures are toxicant and carcinogenic. All 25 possible norfloxacin TPs were predicted mutagenic, toxicant, carcinogenic, and non-readily biodegradable. Results obtained from in silico QSAR models evince the need of performing risk assessment for TPs as well as for the parent antimicrobial. An expert analysis of QSAR predictions using different models and degradation pathways is imperative, for a large variety of structures was found for the TPs.

Degradation of Organic Dyes Using the Ionizing Irradiation Process in the Presence of the CN/CD3/Fe6 Composite: Mechanistic Studies

Organic dyes are ubiquitous pollutants in various aquatic environments as they are produced in abundance and used widely. In the present work, the degradation and mineralization of various organic dyes such as methylene blue (MB), methyl orange (MO), and rhodamine B (RhB), following the electron beam irradiation method in the presence of a graphitic carbon nitride/carbon nanodots/Fe(II) (CN/CD3/Fe6) composite, were studied. The removal efficiency of MB reached 81.7% under conditions of electron beam irradiation (EBI) when the total irradiation dose was 5 kGy. This increased to 91.2% in the presence of the CN/CD3/Fe6 composite. The mineralization efficiency increased from 30.1 to 47.3% when the composite was added, and the total irradiation dose was 20 kGy. The removal efficiency of organic dyes was not significantly affected in the pH range of 3-11. Results from cyclic experiments conducted using MB degradation indicated that the CN/CD3/Fe6 composite exhibited good stability and reusability even after five irradiation cycles. Results from scavenging experiments revealed that •OH was the predominant reactive species during the MB degradation process. Intermediates produced in the synergistic system (EBI&CN/CD3/Fe6 system) consisting of the CN/CD3/Fe6 composite and EBI were detected using the liquid chromatography-mass spectrometry (LC-MS) technique. Based on the results, the possible degradation mechanism and pathways for MB were proposed.

Ecotoxicological Consequences of the Abatement of Contaminants of Emerging Concern by Ozonation—Does Mixture Complexity Matter?

Ozonation has been used to degrade persistent water contaminants, namely, pharmaceuticals and personal care products (PPCPs). However, ozonation can lead to by-products that can be more toxic than the parent compounds. This work aims to assess whether the ecotoxicological effects of ozonation are modified as the initial matrix being treated increases in complexity, considering mixtures of 2, 3, 4 and 5 PPCPs. The following PPCPs were used: two parabens (metylparaben (MP) and propylparaben (PP)), paracetamol (PCT), sulfamethoxazole (SMX) and carbamazepine (CBZ). The following model species were used to assess toxicity: the crustacean Daphnia magna, the microalgae Raphidocelis subcapitata, the macrophyte Lemna minor and the watercress Lepidium sativum. There was a trend of increased toxicity with increasing mixture complexity of the untreated samples, except for D. magna. The same was observed after ozonation with the exception of the mixture MP+PP, which showed high toxicity to all the tested species, namely 100% immobilization of D. magna. The toxicity of SMX to the primary producers decreased pronouncedly after ozonation, except for L. minor. This study highlights the importance of considering the complexity of the matrix being treated and of using an ecotoxicological test battery with a wide diversity of species for assessing ozonation efficiency.

Sulfamethoxazole degradation by alpha-MnO2/periodate oxidative system: Role of MnO2 crystalline and reactive oxygen species

Pollutant degradation via periodate ([Formula: see text]) and transitional metal oxides provides an economical, energy-efficient way for chemical oxidation process in environmental remediation. However, catalytic activation of periodate by manganese dioxide and the associated mechanism were barely investigated. In this study, four MnO₂ polymorphs (α-, β-, γ- and δ-MnO₂) were synthesized and tested to activate [Formula: see text] for the degradation of sulfamethoxazole (SMX). The reactivity of different MnO₂ structures followed the order of α-MnO₂ > β-MnO₂ > γ-MnO₂ > δ-MnO₂, suggesting that the particular crystalline structure in α-MnO₂ would exhibit higher activities via [Formula: see text] activation. Herein, in α-MnO₂/[Formula: see text] system, 91.1% of SMX was eliminated within 30 min with degradation rate constant of 0.0649 min^-1, and the neutral pH exhibited higher efficiency in SMX degradation compared with acidic and alkaline conditions. Singlet oxygen (¹O₂) was unveiled to be the dominant ROS according to the results of electron paramagnetic resonance, chemical probes and radical quenching experiments, whereas [Formula: see text] and ^•OH were mainly acted as a free-radical precursor. Six oxidation products were identified by LC-MS, and the elimination of sulfonamide bond, hydroxylation and direct oxidation were found to be the important oxidation pathways. The study dedicates to the mechanistic study into periodate activation over alpha-MnO₂ and provides a novel catalytic activation for selective removal in aqueous contaminants.

In-situ catalytic degradation of sulfamethoxazole with efficient CuCo-O@CNTs/NF cathode in a neutral electro-Fenton-like system

In this paper, a CuCo-O@CNTs/NF electrode was successfully prepared and used for in-situ degradation of sulfamethoxazole (SMX) in an electro-Fenton-like system. Carbon nanotubes (CNTs) and coral-like copper-cobalt oxides were successively loaded on nickel foam (NF). CNTs contributed to improving the dispersibility and stability of copper-cobalt oxides, and the coral-like copper-cobalt oxide catalyst was anchored on CNTs without any adhesive. In the electro-Fenton-like system, dissolved oxygen can be reduced to superoxide anions in a one-electron step, which could be further transformed into hydrogen peroxide and then reacted with the active components on the electrode to generate reactive oxygen species (ROS) to participate in the degradation of SMX. Almost 100% SMX removal was obtained within 60 min in a wide near-neutral pH range (5.6-9.0), and the electrode could still achieve a 90.4% removal rate after ten recycle runs. Radical-quenching results showed that superoxide anions were the main species in the degradation of SMX. In addition, a possible degradation pathway of SMX was proposed. According to the result of toxicological simulations, the toxicity of the pollutant solution during the degradation process exhibited a decreasing trend. This study provides new insights for in-situ catalysis of electrodes with bimetallic active components to generate ROS for high-efficiency degradation of refractory organic pollutants.

The investigation of influencing factors on the degradation of sulfonamide antibiotics in iron-impregnated biochar-activated urea-hydrogen peroxide system: A QSAR study

Iron-impregnated biochar-activated urea-hydrogen peroxide (FB-activated UHP) is a potential in-situ technology for simultaneously reducing soil sulfonamide antibiotic contaminants and improving soil fertility. To better understand the degradation of sulfonamide antibiotics by FB-activated UHP, a two-dimensional quantitative structure-activity relationship (2D-QSAR) model based on quantum chemical parameters and a three-dimensional QSAR (3D-QSAR) model based on molecular force field were developed to investigate the factors influencing the removal efficiencies (Re%). The optimal 2D-QSAR model was Re%= 0.858-8.930 E-5 E_B3LYP-0.175 f(+)_x with the evaluation indices of R²= 0.732, q²= 0.571, and Q_ext²= 0.673. The given 2D-QSAR model indicated that the molecular size (E_B3LYP) and Fukui index with respect to nucleophilic attack (f(+)) were intrinsic factors influencing Re%. Three degradation pathways were subsequently proposed based on the f(+) distribution. Compared to the 2D-QSAR model, the developed 3D-QSAR model exhibited a better predictive ability, with the evaluation indices of R²= 0.989, q²= 0.696, and SEE= 0.001. The analysis of field contribution rates suggested that electrostatic field (48.2%), hydrophobic field (25.3%), and hydrogen-bond acceptor field (12.7%) were the main factors influencing Re%. These findings generated critical information for evaluating the degradation mechanisms/rules and provided theoretical bases for initially estimating the Re% of sulfonamide antibiotics undergoing FB-activated UHP process.

Effective photocatalytic degradation of sulfamethoxazole using tunable CaCu3Ti4O7 perovskite

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

Formation of stable imine intermediates in the coexistence of sulfamethoxazole and humic acid by electrochemical oxidation

The electrochemical degradation performance of sulfamethoxazole (SMX) was studied in the presence of humic acid (HA) by using a Ti/Ti₄O₇/β-PbO₂ anode. The electrochemical degradation efficiency of SMX decreased from 93.4% to 45.8% in 50 min after the addition of 25 mg L^-1 HA. The pseudo-first-order kinetic rate constant decreased by 71.4%, and the E_EO value increased from 63.8 Wh L^-1 to 90.9 Wh L^-1. HA and its degradation intermediates could compete for free radicals, especially for ·OH, with SMX. The analytical results obtained using UPLC-ESI-Q-TOF-MS showed that 18 degradation intermediates were identified in the coexistence of SMX and HA. Four imine intermediates were formed through the reactions between the aniline moieties of SMX and quinone groups in the HA structure through covalent bonds. Furthermore, the relative abundances of the intermediates demonstrated that the imine intermediates were complex and stable during electrochemical degradation.

Harnessing Paenarthrobacter ureafaciens YL1 and Pseudomonas koreensis YL2 Interactions to Improve Degradation of Sulfamethoxazole

Sulfamethoxazole (SMX) is a widespread and persistent pollutant in the environment. Although the screening and analysis of SMX-degrading bacteria have been documented, the interaction mechanisms of functional microorganisms are still poorly understood. This study constructed a consortium with strain YL1 and YL2 supplied with SMX as the sole carbon and energy source. The coexisting mechanism and the removal of SMX of the consortium were investigated. The total oxidizable carbon (TOC) removal rate of the combined bacterial system was 38.94% compared to 29.45% for the single bacterial system at the same biomass. The mixed bacterial consortium was able to resist SMX at concentrations up to 400 mg/L and maintained a stable microbial structure at different culture conditions. The optimum conditions found for SMX degradation were 30 °C, pH 7.0, a shaking speed of 160 r·min⁻¹, and an initial SMX concentration of 200 mg·L⁻¹. The degradation of SMX was accelerated by the addition of YL2 for its ability to metabolize the key intermediate, 4-aminophenol. The removal rate of 4-aminophenol by strain YL2 reached 19.54% after 5 days. Genome analysis revealed that adding riboflavin and enhancing the reducing capacity might contribute to the degradation of SMX. These results indicated that it is important for the bioremediation of antibiotic-contaminated aquatic systems to understand the metabolism of bacterial communities.

Gamma irradiation-induced degradation and mineralization of methocarbamol in aqueous solution

Gamma irradiation degradation of the extensively used muscle relaxant in the world methocarbamol (MET) was studied. MET aqueous solutions were irradiated by gamma rays emitted by a Cobalt 60 source at doses of 1-4 kGy. Our findings demonstrated that gamma irradiation degraded more than 98.5% of MET. Absorption spectra analysis revealed that when increased irradiation dose, the absorption bands declined with complete disappearance at 4 kGy dose. Additionally, the most radiolytic degradation rate was recorded at neutral pH, marked by Total Organic Carbon (TOC) removal rate of 98% reflecting the total mineralization of MET at 4 kGy. In-depth spectrophotometric analyses advocated a pseudo-first-order type of MET degradation kinetics. The obtained apparent rate constant value was k_{app, MET} = (0.02167 ± 0.0006) min^-1. Gas chromatography-mass spectrometry (GC-MS) allowed the detection of 3-(o-methoxyphenoxy)-1,2 propanediol,2-methoxyphenol, 1,2,3 propanetriol, 1,2-dihydroxybenzene and 1,2,4 benzentriol identified as by-products generated during radiolytic degradation. Finally, an outline of the degradation mechanism was suggested according to the obtained by-products.

Ozone Kinetic Studies Assessment for the PPCPs Abatement: Mixtures Relevance

The increasing consumption of pharmaceutical and personal care products (PPCPs) by humankind has been causing an accumulation of contaminants (commonly referred to as contaminants of emerging concern), in effluents and water resources. Ozonation can be used to improve the removal of these contaminants during water treatment to alleviate this burden. In this work, the degradation of methyl (MP), propylparaben (PP), paracetamol (PCT), sulfamethoxazole (SMX), and carbamazepine (CBZ) by ozonation was assessed both for individual compounds and for mixtures with increasing complexity (two to five compounds). Ozonation was performed at pH3 to gain an insight on the exclusive action of molecular ozone as oxidizing agent. The degradation of contaminants was described as a function of time and transferred ozone dose, and the corresponding pseudo-first order kinetic rate constants (k’) were determined. PPCPs were degraded individually within 1.5 to 10 min. CBZ was the most quickly degraded (k’ = 1.25 min−1) and MP the most resistant to ozone (k’ = 0.25 min−1). When in the mixture, the degradation rate of the contaminants was slower. For parabens, the increase of the number of compounds in the mixture led to an exponential decrease of the k’ values. Moreover, the presence of more PPCPs within the mixture increased energy consumption associated with the treatment, thereby reflecting higher economic costs.

Insight into the rapid elimination of low-concentration antibiotics from natural waters using tandem multilevel reactive electrochemical membranes: Role of direct electron transfer and hydroxyl radical oxidation

Herein, we reported a tandem multilevel reactive electrochemical membrane (REM) system was promising for the rapid and complete removal of trace antibiotics from natural waters. Results indicate that a four-stage REM module-in-series system achieved steady over 98% removal of model antibiotic norfloxacin (NOR, 100 μg·L^-1) from wastewater treatment plant final effluent and surface water with a residence time of 5.4 s, and the electric energy consumption was only around 0.007-0.011 kWh·m^-3. As for the oxidation mechanism, direct electron transfer (DET) oxidation process played an important role in NOR rapid oxidation, enabling the REM system to tolerate various ^•OH scavenges in natural waters, including natural organic matters, Cl^- and HCO₃^-, even at very high concentration levels. Meanwhile, ^•OH-mediated indirect oxidation process promotes the oxidation and mineralization of NOR. Although the DET-dominated oxidation mechanism makes the REM system cannot achieve the complete mineralization of NOR with residence times of few seconds, the antibacterial activity from NOR was completely eliminated. This REM system featured effective removal performance of trace contaminants with low energy cost and was tolerant to complex waster matrix, suggesting that it could be a powerful supplementary step for wastewater/water treatment.

Tannic acid reinforced electro-Fenton system based on GO-Fe3O4/NF cathode for the efficient catalytic degradation of PNP

In order to overcome the sluggish kinetics of the redox conversion between Fe³⁺ and Fe²⁺ in Fenton process, we established a novel electro-Fenton system based on GO-Fe₃O₄ cathode and tannic acid (TA) for the efficient degradation of p-nitrophenol (PNP). Under the optimal degradation parameters (including the initial PNP concentration of 20 mg L^-1, pH = 5, current density of 30 mA cm^-2 and feeding ratio of PNP: TA = 1:2), the TA reinforced GO-Fe₃O₄ electro-Fenton system exhibited the removal rate of PNP over 90.1 ± 0.2%, the COD removal rate of 69.5 ± 0.84% and satisfactory reusability (with the removal rate of ∼80% after 5 recycles). The excellent degradation performance of the proposed TA reinforced GO-Fe₃O₄ electro-Fenton system was partly attributed to the optimized morphology (with the particle size of Fe₃O₄ reduced to tens of nanometers, pore size decreased by ∼80% and pore volume increased by 24.3 times) and larger specific surface area (increased by 72.7 times) after compositing GO with Fe₃O₄, which exposed more active sites. In return, the electron transfer process, the two-electron oxygen reduction reaction (ORR) and the degradation efficiency were promoted in the cooperation of GO and Fe₃O₄. Moreover, the incorporated TA would form a TA-Fe(III) complex to promote the reduction reaction from Fe³⁺ to Fe²⁺, which strengthened the self-circulation of Fe²⁺ and Fe³⁺ and indirectly enhanced the conversion of H₂O₂ to ROS to decompose PNP into smaller organic fragments or mineralize into CO₂, H₂O, NO₂^- or NO₃^-, etc. Obviously, the incorporation of TA provided a promising strategy to improve the electro-Fenton efficiency and realize the efficient removal of PNP in wastewater.

Catalytic ozonation of chloramphenicol with manganese-copper oxides/maghemite in solution: Empirical kinetics model, degradation pathway, catalytic mechanism, and antibacterial activity

The composite material of manganese-copper oxide/maghemite (Mn_xCu_yO_z/γ-Fe₂O₃) was synthesized by the co-precipitation-calcination method. With the initial concentration of 0.2 g/L Mn_xCu_yO_z/γ-Fe₂O₃ and 10 mg/L O₃, the chloramphenicol (CAP, 10 mg/L) could be completely degraded, which was about 2.22 times of that treated with ozonation alone. The contribution of O₃ and hydroxyl radical (•OH) for CAP degradation in the catalytic process was 6.9% and 93.1%, respectively. According to the effects of catalyst dosage, ozone dosage, and pH on the catalytic performance of Mn_xCu_yO_z/γ-Fe₂O₃, a predictive empirical model was developed for the ozonation with the Mn_xCu_yO_z/γ-Fe₂O₃ system. The HCO₃^-/CO₃^2- and phosphates in solution could inhibit the degradation of CAP with the inhibition ratios 8.45% and 13.8%, respectively. The HCO₃^-/CO₃^2- could compete with CAP and react with •OH, and the phosphates were considered as poisons for catalysts by blocking the surface active sites to inhibit ozone decomposition. The intermediates and possible degradation pathways were detected and proposed. The catalytic ozonation could effectively control the toxicity of the treated solution, but the toxicity was still not negligible. Furthermore, Mn_xCu_yO_z/γ-Fe₂O₃ could be easily and efficiently separated from the reaction system with an external magnet, and it possessed excellent reusability and stability.

Catalytic degradation of sulfamethoxazole by peroxymonosulfate activation system composed of nitrogen-doped biochar from pomelo peel: Important roles of defects and nitrogen, and detoxification of intermediates

Nitrogen doping could improve the catalytic performance of carbon materials, in which the nitrogen configuration could be used as active sites for peroxymonosulfate (PMS) activation. Herein, this paper studied how to turn waste to "treasure" by agriculture waste pomelo peel to prepare nitrogen-doped biochar and successfully applied it to advanced oxidation field. The effects of the sodium bicarbonate (NaHCO₃), melamine, and pyrolysis temperature on the catalytic activity of biochar for the removal of sulfamethoxazole (SMX) were investigated. The optimized nitrogen-doped biochar (C-N-M 1:3:4) possessed high specific surface area (SSA, 738 m²/g) and high level of nitrogen doping (nitrogen content 13.54 at%). Accordingly, it exhibited great catalytic performance for PMS activation to remove SMX antibiotic, and 95% of SMX was removed within 30 min. High catalytic activity of C-N-M 1:3:4 was attributed to rich defects, carbonyl group, high content of graphitic N and pyrrolic N, and large SSA, in which non-radical oxidation process based on singlet oxygen (¹O₂) and electron transfer contributed to the SMX degradation. The prepared nitrogen-doped biochar possessed high stability and reusability and the removal efficiency of SMX still reached 80% after four cycles. Additionally, the phytotoxicity assay indicated that the toxicity of degradation intermediates was obviously decreased in the PMS/ C-N-M 1:3:4 system.