Abstract
Photocatalytic method for the treatment of effluents from textile dyeing industries has been investigated. The effect of dyeing auxiliaries on the degradation of the dye was studied. Finally, the treated water was tested for process purposes. The studies on the effect of presence of additives in the dyeing effluents on the photo-removal of dyes showed that sodium nitrate, sodium chloride increase the degradation rate and urea did not affect the degradation rate of the dye; however presence of carbonate decreased the degradation rate. The effluents using vinyl sulphone dyes were simulated in different shades using four commercial textile dyes. The photocatalytic removal of colour of a simulated textile effluent using ZnO suspensions under UV (253.7 nm from a low pressure mercury vapour lamp, 6 W) and solar radiations has been studied in an open-type batch photoreactor. Complete removal of the dye from highly coloured cotton dyeing effluents has been arrived at 8 h under solar radiation and 16 h of UV radiation. The treated water contains only inorganic ions such as carbonate, sulphate, nitrate, ammonium and chloride ions. Studies on the treatment of actual effluents show that complete removal of pollutant has been arrived at 2.5 h under solar irradiation. The treated water can be successfully reused for dyeing purposes.