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

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.