Abstract
A traditional reducing agent in an indigo dyeing process with cotton fabrics is sodium dithionite (Na 2 S 2 O 4 ) 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 Na 2 S 2 O 4 in indigo dyeing. The comparison of reduction power of Na 2 S 2 O 4 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. Na 2 S 2 O 4 could give higher color strength than glucose. However, wash fastness of the fabric samples from a glucose reduction was slightly better than Na 2 S 2 O 4 ones. Hence, glucose virtually has a potential to be used as a green reducing agent in natural indigo dyeing.
Highlights
Natural indigo is an ancient vat blue dye that can be extracted from native indigo-bearing plants, especially from the leaves
Indican is hydrolyzed by enzyme to indoxyl and glucose
In the case of Na2S2O4, as the temperature increased the reduction potential slightly increased in the negative values which is in agreement with Meksi, 2012
Summary
Natural indigo is an ancient vat blue dye that can be extracted from native indigo-bearing plants, especially from the leaves. Indigofera, Isatis tinctoria and Persicaria tinctoria are examples of indigo-bearing plants. Indican is hydrolyzed by enzyme to indoxyl and glucose. HO OH O OH N H Indican Enzyme OH N H Indoxyl Oxidation OH N
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