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The contribution of free radicals in paracetamol degradation by UV/NaClO

UV/Chlorine is an emerging advanced oxidation process which forms several reactive species including •OH, •Cl, •OCl. This study investigated the contribution of three main free radicals: •OH, •Cl, •OCl on Paracetamol degradation under different conditions. Benzoic acid (BA), Nitro benzene (NB) and DMOB were used as probe compounds. The second rate constant of •OH, •Cl, •OCl with PRC were determined: 4.19 (±0.15) ×109 M -1 s -1 ; 3.71 1010 M -1 s -1 ; 3.532×109 M -1 s -1 , respectively. The formation of free radicals depends on pH. | Vietnam Journal of Chemistry, International Edition, 55(6): 720-723, 2017 DOI: 10.15625/2525-2321.2017-00532 The contribution of free radicals in paracetamol degradation by UV/NaClO Le Truong Giang1, Dao Thi Phuong1, Quan Cam Thuy2, Dao Hai Yen1* 1 Institute of Chemistry, Vietnam Academy of Sience and Technology 2 Viet Tri University of Industry (VUI) Received 21 November 2017; Accepted for publication 29 December 2017 Abstract UV/Chlorine is an emerging advanced oxidation process which forms several reactive species including •OH, •Cl, OCl. This study investigated the contribution of three main free radicals: •OH, •Cl, •OCl on Paracetamol degradation under different conditions. Benzoic acid (BA), Nitro benzene (NB) and DMOB were used as probe compounds. The second rate constant of •OH, •Cl, •OCl with PRC were determined: 4.19 (±0.15) ×109 M-1s-1; 3.71 1010 M-1s-1; 3.532×109 M-1s-1, respectively. The formation of free radicals depends on pH. In particular, at pH 5: the contribution of •OH and (-•OCl, •Cl) are 45 %, 41 %, respectively, at pH 8.5, the contribution of free radicals increases up to 63 %. • Keywords. Paracetamol, UV/Chlorine process, reactive species. 1. INTRODUCTION Advanced oxidation processes (AOPs) are attracting many concerns from researchers in water treatment issues. Their capacity to degrade micro pollutants was demonstrated to be more effective than traditional methods such as: coagulation, filtration, bio-degradation [1]. NaClO disinfection combined with UV irradiation is effective, low cost comsuption and widely applied. UV/NaClO generates primary free radicals •OH and •Cl [2] and secondary radicals such as: -•Cl2, HClO•- and •OCl [3, 4]. •OH is non-selective oxidation which has ability to react with micro pollutants in the rate constant from 108-1010 M-1s-1. Chlorine reactive radicals: -•Cl2, •Cl and •OCl are selective oxidants. • Cl prefers to react with substituted aromatics such as : phenol, benzoic acid, toluene and aniline .