Transformation of p,p′–DDT in ethanol under ionizing radiation: Mechanistic and qualitative characterization by GC-MS

In this study, γ-radiolytic degradation of p,p′-DDT in ethanol was investigated under ionizing γ rays from 60 Co source and the results have been reported. Strong dependence of DDT degradation on absorbed dose was observed. Nearly 100% transformation of 0.3 g L –1 initial concentrated DDT has been achieved at absorbed doses above 24 kGy. GC–MS analysis revealed the transient formation of reductive and oxidative conversion products. p,p′-DDD and p,p′-DDMS identified as primary and major intermediates, followed by further transformation into less chlorinated and recombination products at higher absorbed doses. Radiation chemical yields (G-values) confirmed efficient reductive dechlorination, particularly reached maximum, 0.09 µmol J -1 at 12 kGy, while the progressive decrease in G-values at higher doses reflected decrease in concentration of parent compound and secondary degradation of intermediates. Detoxification effectiveness was evaluated using relative toxicity index, which decreased sharply with increasing absorbed dose. It demonstrates simultaneous degradation of initial DDT and its radiolytic byproducts effect on toxicity. Mechanistic analysis indicates that the radiolysis of ethanol generates solvated electrons and hydrogen atoms, drive reductive C–Cl bond heterolytic and homolytic cleavage respectively generate 2-chloro-1,1-diphenylethane, (2,2-dichlorethane-1,1-diyl)-dibenzene, bis(4-chlorophenyl)methane, 1-chloro-4-(chlorophenylmethyl)benzene and dissolved oxygen introduces oxidative pathways leading to hydroxyl, carbonyl and carboxyl based products, 2,2-bis(4-chlorophenyl)ethan-1-ol, DBP and DDA respectively. Compared with conventional methods and advanced oxidation processes, γ-irradiation enables the transformation and detoxification of persistent organochlorine pollutants without the addition of chemical reagents, particularly at low or trace concentrations.