Abstract:
Wastewaters in the experiment were synthesized from seven types of dyes ; namely, direct, vat, reactive, acid, basic, sulfur and azoic. The efficiency in decolorization of the wastewaters by sodium hydrosulfite, hydrogen peroxide and sodium hypochlorite was found to depend on dye types, hue and decolorants themselves. Sodium hydrosulfite efficiency in the color reduction was more than 50 percent for most types of dye wastewaters used in this study, while that for vat wastewater was nil. The efficiency in the decolorization for direct (blue) and reactive (blue) dye wastewaters was very low. Additives had not much effect on the efficiency of decolorization and the optimum contact time should be around 10-30 minutes. Color removal efficiency of hydrogen peroxide solution was very low and it is unlikely to be used for decolorizing the dye wastewaters. Sodium hypochlorite could reduce more than 75 percent of colors present in most dye types. But it is not effective for the insoluble dye, eg. vat, wastewater.