Radical-induced destruction of diethyl phthalate in aqueous solution: kinetics, spectral properties, and degradation eff
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Radical-induced destruction of diethyl phthalate in aqueous solution: kinetics, spectral properties, and degradation efficiencies studies Ning Liu • Gang Xu • Minghong Wu • Xiangxin He Liang Tang • Wenyan Shi • Liang Wang • Haiyang Shao
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Received: 1 May 2012 / Accepted: 17 October 2012 Springer Science+Business Media Dordrecht 2012
•Abstract In this work, the reactions of •OH, eaq, and SO4 with diethyl phthalate (DEP) were investigated in aqueous solution by pulse radiolysis, and degradation efficiencies of DEP with •OH and eaq were evaluated in water using steady-state •radiolysis as well. The absolute rate constants of •OH, eaq, and SO4 with DEP were 9 10 8 -1 -1 determined as 2.3 9 10 , 1.0 9 10 , and 1.0 9 10 M s , respectively. The degradation efficiencies for the •OH and eaq reactions were 81 and 33 %, respectively. Transient absorption spectra were observed for the intermediate radicals •produced by •OH, eaq, and SO4 reactions. The results suggested that eaq transferred to the ester group, resulting in the formation of DEP radical anions. In contrast, •OH and SO•4 added predominantly to the aromatic ring of DEP, forming the corresponding •OH adducts. The fundamental mechanistic parameters and degradation efficiencies derived from these results were significant for evaluations and applications of advanced oxidation processes.
Keywords DEP Transient absorption spectra Absolute rate constant Degradation efficiency
Introduction Phthalate esters (PAEs) are one of the largest groups of endocrine disrupting chemicals used as a plasticizer in polyvinyl chloride plastics and other common consumer products [1]. Significantly, the worldwide production of PAEs is evaluated to be more than 5.2 million tons per year [2]. Meanwhile, plenty of PAEs used in industries are not chemically bound to the host, which may continuously leach from the host polymers, and eventually migrate into the N. Liu G. Xu (&) M. Wu X. He L. Tang W. Shi L. Wang H. Shao School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China e-mail: [email protected]
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environment [3]. Recent studies have revealed that PAEs are not only toxic and mutagenic, but may also have endocrine disrupting effects on aquatic species [4]. Based on their potential harmfulness, some of these compounds have been listed as priority pollutants by the US Environmental Protection Agency (EPA) [5]. Diethyl phthalate (DEP) is one of the most frequently identified PAEs in the environment, which have been detected with elevating concentrations in surface water, drinking water, and sea water [6–9]. There were reports that DEP existed in 71 % of personal care products [10], 57 % of perfumes, and 25 % of deodorants [11]. Moreover, it also existed in various medical devices, and dialysis and intestinal tubing [12]. In order to eliminate DEP from water environments, several advanced oxidation processes (AOPs) based on the generation of highly oxidative hydroxyl radical (•OH), either catalytically or noncata
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