Photo-sensitization of diazo disperse dye in aqueous acetone

Most disperse dyes that are usually used by the textile dyeing industry are resistant to UV degradation. The photodegradation of dyeing wastewater in the presence of acetone, which performs as a solvent and/or a photo-sensitizer, was investigated in this study. The results demonstrated that photochemical reaction in the presence of acetone could rapidly and effectively enhance color removal at a wavelength of 253.7nm. The photo-synthesization follows pseudo first-order decay. The rate constants of dye degradation by UV depended on the solution pH and solvent system, (i.e., acetone to water ratio). The photosensitization of the disperse dye was found to be optimized at pH 9 and in 1:2 (v/v) acetone/water ratio. In addition, the BOD5/COD ratio of the treated solution was increased, indicating that the dye structure was shattered and more biodegradable in the ensuing biological treatment. Acetone in the wastewater could be recycled by a simple gas stripping process, which not only recovered the acetone for reuse but also increased the dissolved oxygen in the wastewater stream and facilitated the biological treatment. (C) 1999 Elsevier Science Ltd. All rights reserved.