One-step ultrasonic-assisted persulfate-percarbonate process for sustainable bleaching of yak wool fibers

Conventional Fe 2+ / H 2 O 2 bleaching process for yak wool fibers poses significant environmental challenges, particularly in water protection, due to its multi-step operations and heavy-metal reliance. This study developed an one-step, low-temperature, metal-free bleaching process utilizing ammonium persulfate (APS) and sodium percarbonate (SPC) assisted by ultrasonic technology (U/APS/SPC). Under optimized conditions, the U/APS/SPC process achieved a whiteness index of 73.7%, representing a 17.6% improvement over the non-ultrasonic process and outperforming the conventional Fe 2+ / H 2 O 2 bleaching process (68.1%). The bleached yak wool fibers preserved their scale structures and maintained high breaking strength (up to 2.31 cN dtex -1 ), meeting the requirements for subsequent processes. Mechanistic analysis indicates that ultrasonic promotes the generation of sulfate (•SO 4 ⁻ ) and hydroxyl (•OH) radicals, accelerating melanin degradation. Meanwhile, the presence of NH 4 + from APS promoted fiber swelling and radical penetration, further improving the bleaching efficiency. Life cycle assessment (LCA) confirmed substantial reductions of U/APS/SPC process in global warming, freshwater ecotoxicity, marine ecotoxicity, and human carcinogenic toxicity compared to the conventional Fe 2+ / H 2 O 2 process. In addition, the U/APS/SPC system simplified operation, lowered energy demand, and ensured dyeability comparable to industrial standards. This work highlights a sustainable and efficient strategy for decolorizing protein-based fibers, contributing to the advancement of cleaner textile production and environmental pollution reduction. • An eco-friendly, one-step bleaching process for yak wool fibers was developed. • The bleaching efficiency of U/APS/SPC outperforms that of conventional Fe 2+ /H 2 O 2 process. • Ultrasonic significantly enhanced the generation of •SO 4 - and •OH radicals. • LCA confirmed that the U/APS/SPC bleaching process reduced the environmental burdens.