Eco-Friendly Dyeing and Finishing for Improving Colour Fastness and Wellness Properties of Cotton

A comparative assessment of the performance of double sequential pre-bio-mordanting was carried out using tannin-rich harda, gall nut, and natural alum for dyeing cotton with catechu. The best performance was obtained by pre-mordanting with 15% gall nut + alum (25:75) applied in sequence, showing better colour yield and moderate colour fastness to wash, light and rubbing as compared to other combinations of dual pre-mordanting for dyeing the cotton with 30% catechu (equivalent to 3% shade depth). Enhancement of colour fastness to washing (1 grade higher) and rubbing (½ grade higher) was observed post-treatment with 2% chitosan or 0.2% nano-chitosan by pad-dry-cure method. Post-treatment on catechu-dyed cotton fabrics with (i) hot aqueous extract, (ii) ethanolic extract (using EtOH + Water −50:50), and (iii) microwave irradiated extract of eucalyptus leaves with lemon juice as catalyst enhances light fastness to 4–5 or 6, antimicrobial rating to 99% reduction for bacteria and UV protection factor (UPF) up to 45–50 as best results, as compared to 2% ZnO/0.2% Nano-ZnO finish as a mineral-based UV absorber and hydroxy-benzotriazole as commercial UV-absorber. This dual bio-pre-mordanting with alum + gall nut and bio-dyeing with catechu, and bio-finishing with ethanolic extract of eucalyptus is found useful for the production of antimicrobial and UV-resistant protective medical textiles as wellness properties of cotton.