Ecofriendly application of coconut coir (Cocos nucifera) extract for silk dyeing

The worldwide resurgence of natural dyes in all fields is due to the carcinogenic effects of effluent loads shed by synthetic industries. Coconut coir (Cocos nucifera) containing tannin as a source of natural colorants has been selected for coloration of bio-mordanted silk under the influence of ultrasonic radiations at various dyeing conditions. For extraction of tannin dye from cocos powder, different media were employed, and dyeing variables such as dyeing time, dye bath pH, dyeing bath temperature, and the effect of salts on dyeing were optimized. For achieving new shades with excellent color characteristics, bio-mordants in comparison with chemical mordants were employed. It has been found that acid-solubilized extract after ultrasonic treatment for 45 min has yielded high color strength, when coconut coir extract of 4 pH from 6g of cocos powder, containing 5g/100mL salt solution as exhaust agent, was used to dye silk at 75°C for 65 min. Among bio-mordants turmeric (K/S=13.828) and among chemical mordants iron has shown excellent results (K/S=2.0856). Physiochemical analysis of fabric before and after US treatment shows that there is no change in the chemical structure of the fabric. It is found that ultrasonic waves have excellent potential to isolate the colorant followed by dyeing and environmental friendly mordanting at optimal conditions, but also the usage of herbal-based plant anchors, i.e., bio-mordants, has made the natural dyeing process more sustainable and clean.