Decolorization of dyes with copper(II)/organic acid/hydrogen peroxide systems

Decolorization of dyes belonging to various groups was carried out using novel free radicals-generating systems consisting of Cu(II), organic acids and hydrogen peroxide. Among the organic acids tested, succinic acid was the most effective. A 24 h incubation in the presence of 10 mM Cu(II), 200 mM succinic acid, and 100 mM H2O2 resulted in 85–95% decolorization of Remazol Brilliant Blue R (RBBR), Reactive Blue, Poly B-411, Chicago Sky Blue, Evans Blue and Methyl Orange. The replacement of Cu(II) with other transition metals was less effective but 78% decolorization was detected in the case of Co(II) and succinic acid. The decolorization is due to the formation of hydroxyl radicals, formed during the decomposition of H2O2 by the metal–ligand complex.