Hydroxyl radical initiated photodegradation of 4-chloro-3,5-dinitrobenzoic acid in aqueous solution

摘要

The phtoderadation of 4-chloro-3,5-dinitrobenzoic acid 9CDNBA) in aqueouphotolysis of H_2O_2 using low or medium pressure Hg arcs 9UV/H_2O_2 process) and (ii) vacuum ultraviolet (VUV) phtolysis of water at 185 nm (low pressure Hg arc with Suprasil envelope) and at 172 nm (Xe-excimer lamp).These processes were shown to be efficient methods for CDNBA mineralization,in contrast to CDNBA photolysis.For the UV/H_2O_2 process,the optimal concentration of H_2O_2 leading to the rastest degradation rate could be evaluated as a function of the initial CDNBA concentration using a simplified equation based on the main reactions involved in the first stages of the degradation process.Chloride ions were produced at the same rate as CDNBA was depleted,independently of the method used for the production of hydroxyl radicals.In contrast,the production of nitrate and nitrite ions was tronly process dependent,the differences being related to the formation of primary reducting intermediates by VUV photolysis of water.