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Insight into the Degradation of Two Benzophenone-Type UV Filters by the UV/H<sub>2</sub>O<sub>2</sub> Advanced Oxidation Process

Du, Erdeng, Li, Jiaqi, Zhou, Siqi, Li, Miao, Liu, Xiang, Li, Huajie
Water 2018 v.10 no.9
UV filters, benzophenones, carboxylation, hydrogen peroxide, hydroxyl radicals, hydroxylation, light intensity, models, oxidation, response surface methodology, ultraviolet radiation
Environmental problems caused by UV filters, a group of emerging contaminants, have attracted much attention. The removal of two typical UV filters benzophenone (BP) and 4,4&prime;-dihydroxy-benzophenone (HBP) in water was investigated by the UV/H<inf>2</inf>O<inf>2</inf> process. The response surface methodology (RSM) and central composite design (CCD) were applied to investigate the effects of the process parameters on the degradation rate constants, including the initial contaminant concentration, H<inf>2</inf>O<inf>2</inf> dose, and UV light intensity. BP is more easily degraded by the UV/H<inf>2</inf>O<inf>2</inf> process. Both processes followed pseudo-first-order kinetics. The results obtained with the built RSM model are in accordance with the experimental results (adjusted coefficients R2(adj)= 0.9835 and 0.9778 for BP and HBP, respectively). For both processes, the initial contaminant concentration (exerting a negative effect) were the most important factors controlling the degradation, followed by H<inf>2</inf>O<inf>2</inf> dose and UV intensity (exerting positive effects). A total of 15 BP degradation products and 13 HBP degradation products during the UV/H<inf>2</inf>O<inf>2</inf> process were identified by LC/MS and GC/MS. A series of OH radical irritated reactions, including hydroxylation, carboxylation, and ring cleavage, led to the final degradation of BP and HBP. Degradation pathways of BP and HBP were also proposed. On the whole, this work is a unique contribution to the systematic elucidation of BP and HBP degradation by the UV/H<inf>2</inf>O<inf>2</inf> process.