Natural dye extraction from T erminalia chebula in aqueous medium for sustainable dyeing and multifunctional properties of dyed silk

Abstract

The renewed interest in natural dyes for textile processing is motivated by the need to reduce the environmental impact associated with synthetic dyes. This work introduces a silk‐dyeing protocol using Terminalia chebula fruit (TCP) as a green mordant, systematically optimised in accordance with green chemistry principles. Compared to a conventional silk dyeing baseline (liquor ratio 1:50, temperature 95°C, 5%–10% o.w.f. metal salt), the optimised protocol employs a 1:30 liquor ratio, operates at 85°C and uses 3–4% owf Al 2 (SO 4 ) 3 . These modifications result in estimated reductions of 40%–50% in water consumption, 20%–25% in energy use and 30%–40% in chemical inputs. Single‐factor and orthogonal optimisation identified optimal extraction conditions (1:30 liquor ratio, 90°C, pH 10, 90 min) and dyeing conditions (85°C, pH 4, 75 min), achieving a colour strength ( K / S ) of 19.55. FTIR analysis suggested Al 3+ ‐mediated coordination between fibroin and chebulinic acid. The dyed silk demonstrates excellent fastness (light: 5; wash/rubbing: 4–5), an ultraviolet protection factor (UPF) of 70 and greater than 99.9% antibacterial efficacy against Escherichia coli and Staphylococcus aureus after 10 laundering cycles. These results suggest TCP as a high‐performance, wash‐durable natural dye alternative, subject to pilot‐scale validation and life‐cycle assessment.