| The hazardous potential of benzophenone (BP)-type UV filters is becoming an issue of great concern due to the wide application of these compounds in many personal care products (PCPs). Despite the endocrine disrupting effects and the environmental occurrences of BP derivatives in aquatic systems, little acute and chronic data is available regarding their effects in aquatic organisms. Furthermore, BP-type UV filters are continuslly released into the water environment, whereas the elimination efficiency is quite limited in wastewater treatment plants. Therefore, to enhance the removal performance of such PCPs and reduce potential risk to the ecosystem, it is necessary to adopt appropriate dvance oxidation process. This investigation will provide insight into the toxicity mechanisms and useful information for assessing the potential ecological risk of BP-type UV filters, and will contribute to a better understanding of advance oxidation process at WWTPs to remove such BP-type UV filter. Concrete work consists of the following four aspects:(1) The acute toxicities of BPs to Photobacterium phosphoreum and Daphnia magna were determined. Next, density functional theory (DFT) and comparative molecular field analysis (CoMFA) descriptors were used to obtain more detailed insight into the structure-activity relationships and to preliminarily discuss the toxicity mechanism. Additionally, the sensitivities of the two organisms to BPs and the interspecies toxicity relationship were compared. Moreover, an approach for providing a global index of the environmental risk of BPs to aquatic organisms is proposed. The results demonstrated that the mechanism underlying the toxicity of BPs to P. phosphoreum is primarily related to their electronic properties, and the mechanism of toxicity to D. magna is hydrophobicity. Additionally, D. magna was more sensitive than P. phosphoreum to most of the BPs, with the exceptions of the polyhydric BPs. Moreover, comparisons with published data revealed a high interspecies correlation coefficient among the experimental toxicity values for D. magna and D. japonica. Furthermore, hydrophobicity was also found to be the most important descriptor of integrated toxicity.(2) To evaluate the potential ecological risk posed by BPs, freshwater fish Carassius auratus were exposed to 0.5 and 5 mg L-1 BPs for 28 d. The oxidative stress induced in livers of Carassius auratus was assessed using four biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), as well as reduced glutathione (GSH). The integrated biomarker response (IBR) was applied to assess the overall antioxidant status in fish. Moreover, liver tissues were also studied histologically. The results showed that 2,4-dihydroxybenzophenone (BP-1) and 2-hydroxyl-4-methoxyl benzophenone (BP-3) significantly induced GST activity and GSH content. Conversely, SOD and CAT activities were found to be significantly inhibited in all toxicant-treated groups after a 7-day exposure. Prolonged exposure to BPs can lead to excess ROS formation finally resulting in oxidative damage, and also inhibit antioxidant capacities in fish liver. According to their IBR values calculated, the hepatic oxidative toxicity followed the order:BP-1> 2,2’,4,4’-tetrahydroxybenzophenone (BP-2)> 2-hydroxyl-4-methoxyl benzophenone-5-sulfonic acid (BP-4)> BP-3. Besides, histopathological results imply that the balance between the oxidative and antioxidant system in fish was broken down during BPs exposure. Overall, this study indicates that the production of free radical is an important mechanism of BPs toxicity in C. auratus.(3) The present study focuses on the influencing factors, transformation mechanism, and toxicity changes during ozonation of BP-4 in aqueous solution. The experiment was systematically investigated under different process conditions and water matrices. Results revealed a strong pH dependence of the oxidation of BP-4. However, inorganic anions (Cl-, NO3-, SO42-), cations (Ca2+, Mg2+) and humic acid had no effect on BP-4 removal within the tested concentrations.14 products were identified by means of high performance liquid chromatography-high resolution mass spectrometry technique. Next, two possible transformation pathways were proposed and further justified by theoretical calculations of frontier electron densities. The reduction of TOC processed much more slowly compared to BP-4 removal. The reaction mixture exhibited a clear inhibition of the bioluminescent bacteria Photobacterium Phosphoreum, indicating the formation of transformation products with higher toxicities relative to BP-4. The effectiveness of BP-4 removal by ozone oxidation in real waters further demonstrates that ozonation is a promising technique to treat BP-4 contaminated waters.(4) Nitrogen (N) and sulfur (S) co-doped multi-walled carbon nanotubes (MWCNTs) were synthesized originating from MWCNTs functionalized by selective oxygenic functional groups (-COOH and-OH) under thermal decomposition conditions, and characterized by SEM, TEM, BET, XPS, XRD, FT-IR and Raman spectroscopy. Results indicated that the functional-COOH groups play an important role in the doping process. Binary (N and S)-doped CNT-COOH (NS-CNT-COOH) showed remarkably enhanced activity in metal-free activation of peroxymonosulfate (PMS) for catalytic oxidation of benzophenone-4 (BP-4), which is-5 times better than that of single (N)-doped CNT-COOH and binary (N and S)-doped CNT, even exceeds that of the metal catalyst CuFe2O4. Several factors affecting the catalytic performance of PMS/NS-CNT-COOH were investigated. Results suggested that catalytic degradation efficiency of BP-4 increased with catalyst load, PMS concentration and reaction temperature. In contrast, NS-CNT-COOH exhibited no obvious catalytic activity to peroxodisulfate (PDS) or H2O2. Based on intermediate detections, the degradation pathway of BP-4 in the PMS/NS-CNT-COOH system was proposed and further justified by theoretical calculations of frontier electron densities. This investigation presents a novel metal-free catalyst for green remediation of emerging contaminants in water. |
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