Degradation of malathion in aqueous solutions using advanced oxidation processes and chemical oxidation

Abstract

Induced degradation of Malathion in aqueous solutions with advanced oxidation processes (AOPs), using ultraviolet irradiation (UV), ozonation and chemical oxidation using (sodium hypochlorite, calcium hypochlorite, monochloride-isocyanuric acid (MCICA), dichloroiso-cyanuric acid (DCICA), trichloroisocyanuric acid (TCICA) was studied. Malathion and its degradation products were extracted using solid phase extraction (SPE) method, identified using GC-MS. Results showed that the degradation of malathion in aqueous solutions followed the first order reaction, and its half life was 2.37, 4.53, 6.64 and 8.84 h under ozonation, UV, 1.5% TCICA and 1.5% DCICA, respectively when malathion solutions treated for 12 h. The concentrations of chemical oxidative substances, active chlorine content and time of treatments had a significant effect on degradation rate of Malathion, which increased with increasing of each. The most enhancement of Malathion degradation was observed in treatment with ozonation, UV, TCICA and DCICA where the dissipations % of the parent compounds were 96, 68.43, 47 and 40.14%, respectively. The intermediates products of Malathion degradation using chemical method were identified as O, O-dimethyl hydrogen phosphorothioate (DMHP) and diethyl succinate. UV leads to formation of dimethyl phosphate (DMP), diethyl succinate and malaoxon. Ozonation leads to formation of phosphorothioic acid, O, O, S-trimethyl ester (PSA), 2-mercapto-succinic acid diethyl ester (MSA) and malaoxon.