Search

Carbamazepine (CBZ) is a widely used anticonvulsant drug that has been detected in aquatic environments. This study investigated the toxicity of its by-products (CBZ-BPs), which may surpass CBZ. Unlike the previous studies, this study offered a more systematic approach to identifying toxic BPs and inferring degradation pathways. Furthermore, quadrupole time-of-flight (QTOF) and density functional theory (DFT) calculations were employed to analyze CBZ-BP structures and degradation pathways. Evaluation of total organic carbon (TOC) and total nitrogen (TN) mineralization rates, revealed carbon (C) greater susceptibility to mineralization compared with nitrogen (N). Furthermore, three rules were established for CBZ decarbonization and N removal during degradation, observing the transformation of aromatic compounds into aliphatic hydrocarbons and stable N-containing organic matter over time. Five potentially highly toxic BPs were screened from 14 identified BPs, with toxicity predictions guiding the selection of commercial standards for quantification and true toxicity testing. Additionally, BP207 emerged as the most toxic, supported by the predictive toxicity accumulation model (PTAM). Notably, highly toxic BPs feature an acridine structure, indicating its significant contribution to toxicity. These findings offered valuable insights into the degradation mechanisms of emerging contaminants and the biosafety of aquatic environments during deep oxidation. [Display omitted] • The rules of CBZ decarbonization and nitrogen removal during UV/H 2 O 2 were deduced. • Key by-products were quantified on concentration and toxicity. • Acridine structure was the main toxic contributor. • Carbon was more likely to be mineralized than nitrogen during degradation. • The degradation pathways were obtained by combing N-transformation and DFT. [ABSTRACT FROM AUTHOR]

Membrane concentrates (MCs) are generated when membranes are used to concentrate landfill leachate. It contains high concentrations of inorganic and organic environmental pollutants, which are highly toxic and carcinogenic. In this paper, the proliferation effect (PE) from MC before and after treatment with the UV-Fenton process was assessed using the human breast carcinoma cell line MCF-7. The highest value of 116% was found at 5% (v/v) concentration after a 10 min reaction. Phthalic acid esters (PAEs) play an important role in the MC estrogenicity. Estrogen simulation solutions (ESS) of PAEs were prepared to simulate the changes in estrogenic active substances during the UV-Fenton process. The ESS degradation conformed to the first-order kinetics model. The estrogenicity decreased after an initial increase until it acted in a non-estrogenic manner. Convincingly, the intermediates were determined by GC/MS, and the estrogenicity was assessed during the degradation process. The estrogenicity was highly related to the generation of intermediates and the PAE concentration. The results provide guidance for UV-Fenton application in MC estrogenicity reduction. [ABSTRACT FROM AUTHOR]

The degradation of tebuconazole (TEB) by UV/H 2 O 2, UV/NaClO, and ozonation was investigated in this research. The experimental findings unveiled that under the specified conditions, the degradation percentages of TEB were raised to 99% within 40 s, 5 min, and 3 min for UV/H 2 O 2 , UV/NaClO and ozonation, respectively. The mineralization percentages within 1 h were 59%, 31% and 8% for the three AOPs. UV/H 2 O 2 and UV/NaClO technologies mainly acted through OH·, while O 3 treatment primarily relied on the free radicals such as 1O 2 and O 2 ·-. UV-based AOPs achieved almost complete dechlorination within 1 h, whereas O 3 treatment had a less effective dechlorination, reaching only 27.61%. Notably, UV alone achieved a dechlorination percentage of 43.07%. By identifying the TPs, we found that the three AOPs shared three similar degradation pathways. The degradation mechanism of TEB mainly entailed the removal of the benzene ring, tert -butyl group and triazolyl group. Toxicity assessment revealed an initial increase followed by a gradual decrease in toxicity for UV/NaClO and O 3 treatments, whereas UV/H 2 O 2 treatment exhibited a sustained decrease. This was due to the presence of TP278 and TP303 by UV/NaClO and TP168 and TP153 by ozonation. After estimating the costs of the three AOPs, UV/H 2 O 2 standed out as the best choice for achieving a 90% degradation percentage and exhibiting lower toxicity performance, while O 3 treatment was favored for low TOC demands. These research findings provided valuable reference for understanding the degradation mechanism and developing a new technology of the removal of TEB. [Display omitted] • Oxidant-mediated radicals attacked TEB, yielding diverse degradation pathways. • UV/H 2 O 2 was proved cost-effective, while ozonation was favored for low TOC demands. • Conjugated structure of TEB molecule induced its photolysis and dechlorination. • TP153 and TP181 potentially led to lower dechlorination rates by ozonation. [ABSTRACT FROM AUTHOR]

Remdesivir (RDV), dexamethasone (DEX) and hydroxychloroquine (HCQ) were widely used in the treatment of COVID-19 pneumonia, possibly causing environmental risks and drug-resistance viruses. This study elucidated the degradation mechanisms and potential toxicity risks of the three anti-COVID-19 drugs by UV and ultraviolet-coupled advanced oxidation processes (UV/AOPs). All the drugs could be degraded by more than 98% within 3 min under the following optimal conditions: pH of 5.0 and drug-to-oxidant (H 2 O 2) molar ratio of 1:200. Combined with density functional theory (DFT) analysis and high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS), twenty-four transformation products (TPs) were detected and the main degradation pathways were investigated. Based on bacterial luminescence inhibition test and the peak-area evolution of TPs, RDV and HCQ showed an obvious toxicity-increase region when TPs were generated in large quantities, while the toxicity of DEX continued to decline during degradation processes. By QSAR predictions, the main contributors to the toxicity evolution during the UV/AOPs were predicted. Halogen-containing TPs showed significantly higher toxicity than other TPs, and thus the chlorine-containing structure in HCQ presented the potential toxicity. Appropriate reaction parameters and adequate reaction time for the UV/AOPs could eliminate the toxicity of TPs and ensure environmental safety. This study could play a positive role in the treatment of anti-COVID-19 drugs and their environmental hazard assessment. [Display omitted] • Decomposition kinetics and optimal reaction conditions during UV/AOPs for anti-COVID-19 drugs. • 24 TPs and degradation pathways were proposed by DFT and QTOF. • Toxicity data of RDV in QSAR was supplemented by luminescent bacterial test. • Combined QSAR prediction, luminescent bacterial tests and TPs peak area evolution to analyze TPs' toxicity. • Halogen groups contributed to the TPs' toxicity of HCQ. [ABSTRACT FROM AUTHOR]

Four common refractory pharmaceuticals, diclofenac (DF), sulpiride (SP), sulfamethoxazole (SMX) and sulfisomidine (SIM) were detected in the Disc Tubular Reverse Osmosis (DTRO) concentrates with higher concentrations ranging from 0.85 to 11.57 μg/L from the local landfill. The effect of complex matrix of DTRO concentrates on the UV-Fenton degradation kinetics of DF, SP, SMX and SIM and their transformation products (TPs) were studied. All the four pharmaceuticals could be degraded more efficiently in the ultrapure water than that in the DTRO-concentrate matrix, which also had a significant negative effect on the kinetic constants of the degradation. Twenty-two out of forty-nine TPs were newly identified by HPLC-QTOF-MS and their peak-area evolution was presented. The main degradation pathways for four pharmaceuticals were identified. When assessing cytotoxicity by using HepG2 cells, there appeared to be an obvious toxicity-increase region for each of SP, SMX and SIM. Eleven TPs were identified as the potential toxicity-increase causing TPs by combination of the QSAR prediction, HepG2 cytotoxicity assessment and peak-area evolution of TPs. Therefore, UV-Fenton process was a promising method for the refractory pharmaceutical degradation even in the complex water matrix and choosing appropriate reaction parameters for the UV-Fenton could eliminate the cytotoxicity of the TPs. Image 1 • Effect of DTRO concentrates on the UV-Fenton degradation of DF, SP, SMX and SIM was assessed. • 22 TPs were newly identified and the main degradation pathways were proposed. • An obvious toxicity-increase region appeared for degradation of SP, SMX and SIM, assessing by HepG2 cells. • Combination of QSAR prediction, HepG2-cytotoxicity assessment and peak-area evolution of TPs. • The potential toxicity-increase causing TPs were identified. [ABSTRACT FROM AUTHOR]

This study aimed to achieve toxicity control of sulfadiazine (SDZ) and pirimiphos-methyl (PMM) via the UV/H 2 O 2 process by optimizing the reaction parameters. The results show that both drugs had a good degradation effect under the following parameters: a H 2 O 2 molar ratio of 1:200, and neutral conditions. SDZ and PMM could be degraded by more than 99% within 3 min, respectively. In the Daphnia magna acute toxicity assay and Vibrio fischeri inhibition assay, both SDZ and PMM exhibited a phenomenon of increasing toxicity. Additionally, through the use of density functional theory (DFT) calculation and HPLC-QTOF-MS, 21 transformation products (TPs) were identified, and the principal degradation pathways were proposed. The toxicity of the TPs was determined by comparing the QSAR prediction results with toxicity test data. As a result, under the higher UV light intensity (2300 μW/cm2) and neutral conditions, SDZ showed highest toxicity, whereas PMM showed lowest toxicity under the lowest UV light intensity (450 μW/cm2) and neutral conditions. Four main toxic TPs were identified, and their yields could be reduced by adjusting the reaction parameters. Therefore, the selection of appropriate reaction parameters could reduce the production of toxic TPs and ensure the safety of water environment. [Display omitted] • Toxicity of SDZ and PMM was assessed by Daphnia magna and Vibrio fischeri. • 21 TPs and degradation pathways were proposed by DFT and QTOF. • Nitrogenous groups were potential contributors to the TPs' toxicity in SDZ and PMM. • Eliminating 4 toxicity-causing TPs was verified to be effective for toxicity control. [ABSTRACT FROM AUTHOR]

Drawing on the robust activation activity and affinity that transition metal ions and MoS 2 exhibit towards peroxymonosulfate (PMS), 1T/2H hybrid molybdenum disulfide doped with Fe3+ (Fe3+/N–MoS 2) was synthesized to activate PMS for the treatment of organic wastewater. The ultrathin sheet morphology and 1T/2H hybrid nature of Fe3+/N–MoS 2 were confirmed by characterization. The (Fe3+/N–MoS 2 + PMS) system demonstrated excellent performance in the degradation of carbamazepine (CBZ) above 90% within 10 min even under high salinity conditions. By electron paramagnetic resonance and active species scavenging experiments, it was inferred that SO 4 •─ palyed a dominant role in the treatment process. The strong synergistic interactions between 1T/2H MoS 2 and Fe3+ efficiently promoted PMS activation and generated active species. Additionally, the (Fe3+/N–MoS 2 + PMS) system was found to be capable of high activity for CBZ removal in high salinity natural water, and Fe3+/N–MoS 2 exhibited high stability during recycle tests. This new strategy of Fe3+ doped 1T/2H hybrid MoS 2 for more efficient PMS activation provides valuable insights for the removal of pollutants from high salinity wastewater. [Display omitted] • Fe3+ doped 1T/2H hybrid molybdenum disulfide (Fe3+/N–MoS 2) was constructed. • Fe3+/N–MoS 2 showed excellent catalytic performance in high salinity conditions. • Synergistic effects and redox cycles could promote PMS activation. • SO 4.•─ was identified as dominant active species involved in the CBZ degradation. [ABSTRACT FROM AUTHOR]

The wide use and distribution of sulpiride (SP) has caused potential threats to the water environment and human health. In this study, ultrathin S-doped graphitic carbon nitride nanosheets (US–CN) was successfully synthesized and characterized, and its SP removal efficiency was evaluated under various conditions via the visible-light-assisted peroxydisulfate (PDS) activation method. The degradation pathways and mechanism were also discussed through quenching experiments, density functional theory (DFT) calculations, and intermediate products detection. After sulfur doping and ultrasonic treatment, graphitic carbon nitride (CN) possessed an ultra-thin and porous structure, which facilitated the electronic distribution and more photocurrent, thus resulting in the excellent stability and removal efficiency for SP via PDS activation upon visible light irradiation. The singlet oxygen (1O 2) generated by the US-CN/PDS/VL system played a significant role in SP degradation. Based on the bonds of electron-rich atoms fracturing and the SO 2 extrusion, the SP degradation pathway was proposed. This work provides a useful information for the SP photocatalytic degradation via PDS activation. Image 1 • US-CN was synthesized for efficient PDS activation. • The singlet oxygen (1O 2) played a major role in the SP degradation. • Bonds of electron-rich sites atoms (9 N, 12 N, 17O) of SP were fractured. • SO 2 extrusion products were generated from the process of SP degradation. • SP degradation pathway during US-CN/PDS/VL system was proposed. [ABSTRACT FROM AUTHOR]