Mordant-Free Dyeing of Organic Cotton Using Tea Extracts: Waste-to-Color

The valorization of green tea waste as a sustainable natural dye for organic cotton fabrics offers a promising alternative to synthetic dyes, mitigating environmental and health risks. We developed a mordant-free, ultrasonic-assisted dyeing protocol that maximizes dye uptake and fastness while minimizing energy consumption. Systematic optimization revealed 55 °C as the ideal dyeing temperature, achieving superior color strength (K/S = 1.445) and excellent wash and rub fastness without compromising fiber integrity. Mechanistic insights from physicochemical analyses demonstrated enhanced polyphenol–cellulose interactions facilitated by ultrasonic cavitation. This eco-friendly approach promotes circular bioresource utilization and advances green textile coloration.