The role of reactive oxygen species and carbonate radical in oxcarbazepine degradation via UV, UV/H2O2: Kinetics, mechanisms and toxicity evaluation.

Oxcarbazepine (OXC) is ubiquitous in the aqueous environment. And due to its ecotoxicological effects and potential risks to human, an effective way to eliminate OXC from aqueous environment has aroused public concerns in recent years. Radical-based reactions have been shown to be an efficient way for OXC destruction, but the reactions of OXC with reactive oxygen species (ROS) and carbonate radical (CO3•-) are still unclear. In this study, we focused the degradation of OXC and ROS, CO3•- generation mechanism, and their roles in OXC degradation via UV and UV/H2O2. The triplet state of oxcarbazepine (3OXC∗) was found to play an important role in OXC degradation via UV. And hydroxyl radicals (•OH) and singlet oxygen (1O2) were found to be the dominant ROS in OXC degradation. Superoxide radical (O2•-) did not react with OXC directly, but it may react with intermediate byproducts. Generation of CO3•- played a positive role on OXC degradation for both UV and UV/H2O2. In addition to •OH, 3OXC* also contribute to CO3•- production. The second-order rate constants of OXC with •OH and CO3•- were 1.7 × 1010 M-1 s-1 and 8.6 × 107 M-1 s-1, respectively. Potential OXC degradation mechanisms by •OH were proposed and included hydroxylation, α-ketol rearrangement, and benzylic acid rearrangement. Compared with non-selective •OH, the reactions involving CO3•- are mainly electron transfer and hydrogen abstraction. And the acute toxicity of OXC was lower after UV/H2O2 and UV/H2O2/HCO3- treatments, which was confirmed by luminescent bacterial assay (Vibrio fischeri bacterium).

Prednisolone degradation by UV/chlorine process: Influence factors, transformation products and mechanism.

Prednisolone (PDNN) as an emergent micropollutant directly influences the regional ecological security. In this study, the degradation of PDNN by ultraviolet activated chlorine (UV/chlorine) oxidation process was comprehensively evaluated. The quenching experiment suggested that the PDNN degradation in UV/chlorine process was involved in the participation of hydroxyl radical (OH) and reactive chlorine species (RCS). Influence factors including chlorine dosage, pH, common anion and cation, fulvic acid (FA) on PDNN degradation via UV/chlorine process were investigated. A low chlorine (≤7.1 mg L-1) promoted the PDNN degradation, while a high chlorine dosage (>7.1 mg L-1) was adverse. The pH (4.0-10.0) showed negligible effect, while the investigated anions (Cl-, Br-, HCO3- and SO42-), NH4+ and FA exerted negative impact on PDNN degradation. An efficient process to minimize pharmaceutical micropollutants was the disposal of human urine containing a high concentration of pharmaceutical and potential toxic metabolites. An inhibitory effect was observed in the synthetic urine (fresh urine and hydrolyzed urine). The intermediates/products were identified and the mechanism of PDNN degradation was proposed. PDNN gone through three degradation routes, involving the direct addition of α, ß-unsaturated ketone at C1 or C5, the photolysis of C17 and H-abstraction of C11. The main reactive sites were further determined by comparison of the frontier orbitals calculation and the proposed mechanism. Based on the toxicological tests for PDNN degradation, TP396 (TP396-C1Cl and TP396-C5Cl) and TP414-2-1 (TP414-C1ClC5OH) exhibited much higher toxicity than PDNN, and prolonging reaction time was necessary to achieve PDNN detoxification.

Rapid Analysis of Bisphenol A and Its Analogues in Food Packaging Products by Paper Spray Ionization Mass Spectrometry.

In this study, a paper spray ionization mass spectrometric (PS-MS) method was developed for the rapid in situ screening and simultaneous quantitative analysis of bisphenol A and its analogues, i.e., bisphenol S, bisphenol F, and bisphenol AF, in food packaging products. At the optimal PS-MS conditions, the calibration curves of bisphenols in the range of 1-100 µg/mL were linear. The correlation coefficients were higher than 0.998, and the LODs of the target compounds were 0.1-0.3 µg/mL. After a simple treatment by dichloromethane on the surface, the samples were analyzed by PS-MS in situ for rapid screening without a traditional sample pretreatment procedure, such as powdering, extraction, and enrichment steps. The analytical time of the PS-MS method was less than 1 min. In comparison with conventional HPLC-MS/MS, it was demonstrated that PS-MS was a more effective high-throughput screening and quantitative analysis method.

Oxidative transformation of artificial sweetener acesulfame by permanganate: Reaction kinetics, transformation products and pathways, and ecotoxicity.

Acesulfame has attracted much attention due to its wide application, environmental persistence and potential safety risk of transformation products (TPs). Little information is known on acesulfame transformation in the presence of oxidants/disinfectants. The acesulfame oxidation by permanganate (Mn(VII)) in water under environmentally relevant conditions was systematically evaluated. The pH of water showed negligible influence in acesulfame oxidation. Inorganic ligand (pyrophosphate) exhibited insignificant effect whereas organic ligands (oxalate, ethylene diamine tetraacetic acid, and humic acid) exerted obvious suppression on acesulfame oxidation. Natural organic matter in real water had important influence in acesulfame oxidation by Mn(VII). Acesulfame transformation pathways were initiated by the attack of Mn(VII) on double bond of ring via [3+2] addition electrocyclic reaction and rich electron of N moiety through electrophilic reaction, followed by oxidation and hydrolysis reactions to produce TPs. Among them, five TPs were for the first time identified. The ecotoxicity tests uncover higher toxicity of the TPs than acesulfame itself. The study on oxidative transformation of acesulfame by Mn(VII) would illumine comprehensive evaluation of this emerging contaminant. Water treatment plants need to consider cautiously to protect the safety of downstream system when using Mn(VII) to dispose the water resource containing acesulfame or other artificial sweeteners.