High sorption of reactive dyes onto cotton controlled by chemical potential gradient for reduction of dyeing effluents

This research uses soybean oil/water dual-phase solvents system (SWDS) to achieve high dye fixation as well as minimal discharge of waste effluents. Reactive dyeings are one of the most serious pollution sources and few dyeing technologies developed could successfully reduce the generation of toxic substances without decreasing dyeing qualities. Through a remarkable increase in chemical potential of dyes in dyeing medium, SWDS remarkably increased the dye concentration in the internal solvent phase. As a result, % exhaustion of dye was 100%, and % fixation of dye was up to 92% in SWDS. Final discharges of dyes and salts from SWDS were decreased by 85% and 100%, respectively, compared to that from the conventional aqueous system. More than 99.5% of initially added biodegradable soybean oil could be recycled for reactive dyeing without treatments. Furthermore, SWDS could be readily applied in jet-dyeing machines on a pilot scale. Via the reuse of soybean oil, SWDS could save up to $0.26 per kg of fabric compared to aqueous dyeings in terms of materials cost.