Degradation of Reactive Dyes by Photoactive Hydrogen Peroxide Oxidation with Ultraviolet Radiation Lídia Yokoyama 1* , Fabiana V.F. Araujo 1 , Luiz A. C. Teixeira 2 1 Escola de Química – Universidade Federal do Rio de Janeiro 2 Departamento de Ciências dos Materiais e Metalurgia – Pontifícia Universidade Católica-RJ Abstract. This work aimed at the discoloration of textile wastewater, containing the reactive dye Red Drimarene X-6BN 150, using UV irradiation in presence of hydrogen peroxide. The UV/H 2 O 2 oxidation process is a feasible and efficient alternative for wastewater treatment from recalcitrant compounds such as reactive dyes. The experiments were conducted using a 24 factorial design for evaluation of the influence of pH, H 2 O 2 , urea and NaCl concentrations in the efficiency of the discoloration process. The results were expressed in percentage of color removal from solution by measurement of absorbance. The H 2 O 2 /UV process was effective for reactive dye degradation, reaching 99% dye removal, in specific conditions. The H 2 O 2 concentration presented mainly significant positive influence on the process. Otherwise, the NaCl concentration had a negative effect in all experiments, decreasing the percentage of color removal from reactive dye. The pH and urea concentration didn’t influence the discoloration process. Keywords: Reactive dyes, discoloration, hydrogen peroxide, UV radiation. 1. Introduction The textile industry produces high levels of environmental contamination, due to high toxicity of chemical components of wastewaters. These effluents are particularly characterized by high chemical oxygen demand (COD), presence of suspended solids, and strong color, the latter being related with the type of dye used for fiber dying and its water solubility. Reactive dyes have been largely used in the textile industry for dying cellulose and cotton fibers. They form stable covalent bonds with the material they dye and impart the final product a bright and lasting color. However, this class of dyes present a low degree of fixation onto the fibers during dying, thus causing a loss of up to 50% dye in the generated effluent (Cooper, 1995). In addition to a high coloration, reactive dye-containing textile effluents present a low ratio of BOD to COD (<0.4), which indicates their resistance to conventional biological treatments (Koch et al, 2002). Using conventional physical and chemical methods of effluent treatment, e.g. activated carbon, chemical coagulation, and reverse osmosis, has brought a certain positive result on discoloration process, but these systems merely transfer effluent contaminants to a solid phase. Thus, creating other environmental problems requiring further treatment (Neamtu et al, 20022 and Mohey El Dein et al, 2003). Advanced Oxidative Processes (AOP) are a technology object of vast study for recalcitrant substance degradation and have presented good results in respect of discoloring reactive dye- containing wastewaters. These processes encompass a number of emergent methodologies viewing production of free hydroxyl (OH • ) radical, a highly reactive, nonselective oxidizing agent (E H ~ * Adress: Escola de química, UFRJ – Centro de Tecnologia, Bl. E, 21949-900 Rio de Janeiro – Brazil. E-mail: lidia@eq.ufrj.br 1