Reductive degradation of chlorophenols in aqueous solution by gamma irradiation

Because chlorine is an electron withdrawing group,the highly chlorinated phenols may react quickly with hydrated electrons rather than with hydroxyl radicals.The process of reactions of four chlorophenols(4-CP,2-CP,2,4-DCP,2,4,6-TCP) with e-aq was investigated in aqueous solutions by detecting the concentration of CPs,Cl-and intermediates.In the e-aqreductive system,the experimental results showed that the order of four kinds of chlorophenol degradation and dechlorination was 2,4,6-TCP2,4-DCP2-CP4-CP.The greater the chlorine content was the higher reactivity of hydrated electrons towards chlorophenols was.Furthermore,hydrated electrons may preferentially attack the ortho-position of chlorine atom rather than the para-position of chlorine atom.Phenol and Cl-were detected as the final product of the reductive reaction.Additionally,processes of degradation and dechlorination of CPs were observed as the pseudo-first-order kinetics.The reaction constant of degradation of 4-CP,2-CP,2,4-DCP and 2,4,6-TCP were 0.154,0.253,0.750 and 1.188 kGy-1,respectively.Meanwhile,the dechlorination of 4-CP,2-CP,2,4-DCP and 2,4,6-TCP were 0.137,0.219,0.251 and 0.306 kGy-1,respectively.