Comparison of sodium dithionite and glucose as a reducing agent for natural indigo dyeing on cotton fabrics

Abstract

A traditional reducing agent in an indigo dyeing process with cotton fabrics is sodium dithionite (Na2S2O4) which is environmentally unfavorable because the resulting by-products cause various problems to the disposal wastewaters. In this research, glucose was used as a possible replacement of Na2S2O4 in indigo dyeing. The comparison of reduction power of Na2S2O4 and glucose for natural indigo dyeing on cotton fabrics based on reduction potential was analyzed. The optimum reduction temperature for natural indigo dye of both reducing agents was at 70°C. The reduction time did not have a significant effect on the reduction potential under the condition studied. Na2S2O4 could give higher color strength than glucose. However, wash fastness of the fabric samples from a glucose reduction was slightly better than Na2S2O4 ones. Hence, glucose virtually has a potential to be used as a green reducing agent in natural indigo dyeing.