Silk functionalization via Yunnan black tea waste with bio-mordants

Yunnan black tea waste (YBTW) is an underutilized and abundant biological resource, which provides a sustainable dyeing strategy for silk functionalization. This study developed a green process that combines natural dyes extracted from YBTW with bio mordants to oxidize catechins into thearubigins and theaflavins, achieving effective coloring without metal mordants. The binding mechanism of theaflavins on silk fabrics was elucidated at the molecular level using DFT theory. Dyed silk fabrics have excellent color fastness (grades 4–5), meet industrial durability standards, and possess UV protection (UPF 65.91), antioxidant activity (94%), and antibacterial properties (8.8 mm inhibition zone). Finally, the differences in chromaticity and functionality between YBTW and YAGT direct dyed silk fabrics were compared. This work establishes a scalable circular economy framework for the production of environmentally friendly textiles.