Decolorization and Mineralization of Textile Effluent by H2O2/Ultraviolet Processes

This article evaluates the H2O2/UV process for the removal of color and dissolved organic carbon (DOC) from textile effluent samples in a batch UV photoreactor. Experimental variables studied include pH, hydrogen peroxide dosage, oxidation time, and UV intensity. Results show that the H2O2/UV process showed better removal of DOC and color at pH 4 than at pH 7, suggesting that the pH should be controlled at both 4 and 7 for color removal, whereas only at 4 for DOC removal. Oxidation time was extended to 30 and 60 min, respectively, which resulted in removal of more than 70% of the color and DOC. Color and DOC removal followed pseudo first-order kinetics and the reaction rate constants increased with increasing both H2O2 dosage and UV intensity. Increase of H2O2 dosage is more efficient than the increase of UV intensity for promoting the treatment performance of the H2O2/UV process. Further, about 80% of DOC with a high molecular weight (MW) fraction was oxidized into DOC with medium and low MW fractions. DOC with low MW fractions predominated more than 60% of the residual DOC. Therefore, the oxidation of DOC with a high MW fraction into medium and low MW fractions was more important than the mineralization of DOC by H2O2/UV oxidation.