Simultaneous recovery of copper and degradation of 2,4-dichlorophenoxyacetic acid in aqueous systems by a combination of electrolytic and photolytic processes

In mixed industrial effluent the presence of metal ions can retard the dest ruction of organic contaminants and the efficiency of recovery of the metal is reduced by the presence of the organic species. Results are presented f or copper-2, 4-dichlorophenoxyacetic acid (2,4-D) system in which both effe cts occur. An electrochemical cell alone can be used to recover copper in t he pH range 1.5-4.5 but it is not capable of achieving complete disappearan ce of 2,4-D by anodic oxidation. A photolytic cell alone can achieve the de struction of 2,4-D at pH 3.5 but leaves copper in solution. A combined phot olytic-electrochemical system using an activated carbon concentrator cathod e achieves the rapid simultaneous destruction of 2,4-D and recovery of copp er. Results are presented for the recovery of more than 90% copper from, an d >99.9% destruction of the organochlorine compound 2,4-D in, a solution co ntaining 100 mg dm(-3) copper and 50 mg dm(-3) 2,4-D. The photolytic degrad ation of 2,4-D depends on the intensity of the UV-probe. Only 19% degradati on is achieved after 8 h with the 150 W UV-probe but the corresponding valu e with the 400 W UV-probe is 100%. In the case of 150 W UV-probe the degrad ation of 2,4-D proceeds through the formation of 2,4-dichlorophenol and phe nol. The concentration of these intermediates are very low in the case of 4 00 W UV-probe because the speed of the degradation of 2,4-D is very fast. T he addition of TiO2 (1 g dm(-3)), as a semiconductor material, and H2O2 (1. 5 g dm(-3)) as an oxidant, increases the photolytic degradation of 2,4-D. ( C) 2001 Elsevier Science Ltd. All rights reserved.