title: Self-enhanced ozonation of benzoic acid at acidic pHs.
abstract: Ozonation of recalcitrant contaminants under acidic conditions is inefficient due to the lack of initiator (e.g., OH(-)) for ozone to produce hydroxyl radicals (HO). In this study, we reported that benzoic acid (BA), which is inert to ozone attack, underwent efficient degradation by ozone at acidic pH (2.3). The kinetics of BA degradation and ozone decomposition were both enhanced by increasing BA concentrations. Essentially, it is a HO-mediated reaction. Based on the exclusion of possible contributions of H2O2 and phenol-like intermediates for HO production, the reaction mechanism involved the formation of ozone ion ( [Formula: see text] ), which is an effective precursor of HO, was thus proposed. The hydroxycyclohexadienyl-type radicals generated during the attack of BA by HO may lead to the formation of [Formula: see text] . Meanwhile, [Formula: see text] could also be possibly formed from the reaction between ozone and organic (e.g., ROO∙) or inorganic peroxyl radicals (e.g., HO2). In addition, the hydroxylated products like phenol-like intermediates also played a positive role in HO production. Consequently, HO was produced efficiently under acidic conditions, resulting in rapid degradation of BA. This study provides a new approach for ozone activation even at acidic pHs, and broadens the knowledge of ozonation in removal of micropollutants from water.
authors: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors: Xianfeng
authors: X
authors: Huang
authors: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China; School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, China.
authors: Xuchun
authors: X
authors: Li
authors: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China. Electronic address: bcpan@nju.edu.cn.
authors: Bingcai
authors: B
authors: Pan
authors: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors: Hongchao
authors: H
authors: Li
authors: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors: Yanyang
authors: Y
authors: Zhang
authors: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors: Bihuang
authors: B
authors: Xie
mesh_terms: D019817:Benzoic Acid / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000032:analysis; D010126:Ozone / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D010126:Ozone; D019817:Benzoic Acid
keywords: Acidic conditions; Advanced oxidation process; Benzoic acid; HO; Ozone