Degradation of commercial reactive dyestuffs by heterogenous and homogenous advanced oxidation processes: a comparative study

Advanced oxidation of the commercially available reactive dyestuffs Remazol Black B and Remazol Turquoise Blue G 133 in aqueous solution with TiO2-med iated photocatalytic and photoinduced and dark Fenton/Fenton-like reactions has been studied. Initial decolourization rates, effectiveness in removal of UV254 (nm), COD as well as TOC were compared and evaluated. It was found that all advanced oxidation systems were capable of completely decolourizi ng the azo dye Remazol Black in feasible treatment times and at concentrati ons typically found in dyehouse effluents, whereas COD and TOC removal effi ciencies ranged between 77-98% and 51-86%, respectively. Photo-Fenton's oxi dation gave the best decolourization reaction, which proceeded 20 times fas ter than TiO2-mediated photocatalytic oxidation. Moreover, photocatalytical treatment of Remazol Black followed the empirical Langmuir-Hinshelwood kin etics in the concentration range 25-100 mg/l. However, none of the advanced oxidation systems was effective in the degradation of the copper phthalocy anine dye Remazol Turquoise Blue for which colour and COD removal was mainl y attributable to adsorption on the photocatalyst surface or the coagulatin g effect of iron applied in the homogenous advanced oxidation reactions. (C ) 1999 Elsevier Science Ltd. All rights reserved.