SOLAR NANOPHOTOCATALYTIC DECOLORISATION OF REACTIVE DYES USING TITANIUM DIOXIDE

Abstract

The discharge of dye-bearing wastewater from textile industries into natural streams and rivers poses several problems. Some dyes are toxic to aquatic life, may damage aesthetic nature of the environment and are difficult to be treated by conventional methods. The present work investigated the photodecolorization of reactive dyes by solar nanophotocatalysis. Nano-TiO2 was prepared using a sol-gel method and their surface state was analyzed by X-ray diffractometer. Procion Reactive Red (H-E7B) and Procion Reactive Yellow (H-E6G) were used as model compounds. The effects of operational variables such as catalyst type and dose, pH, contact time, H2O2, anions (C1-, SO42- and CO32-), solar light intensity and catalyst reuse were investigated. The complete color removal was achieved at optimum conditions of catalyst dose of 160mg/L, pH=5.5 and contact time = 95 min for dye sample H-E7B and catalyst dose of 500 mg/L, pH=7.4 and contact time = 150 min for dye sample H-E6G, respectively. At optimum conditions, COD reduced from 120 mg/L to 23 mg/L and from 108 mg/L to 17 mg/L for the two types of dye, respectively. Kinetic analyses indicated that photocatalytic decolorization rate a followed a first-order model.