Sustainable Valorization of Grape-Leaf-Based Flavonoid Natural Dye Molecules for Eco-Friendly Wool Yarn Dyeing

The utilization of plant isolates as dyes in applied fields has gained considerable interest due to growing environmental concerns associated with the toxic synthetic dyes. In the present work, the agro-waste (such as grape leaves) has been valorized as a rich source of flavonoid-based natural dye for sustainable dyeing of woolen yarn. Microwave irradiation was further applied to dye molecules and wool yarn to enhance the dye uptake and process efficiency. Processing parameters for dyeing were optimized using Box-Behnken as a statistical design, and the results of the analysis revealed that the processing parameters, including temperature (80 °C), time (25 min), pH 5, and salt concentration (3 g/100 mL), significantly influence the color strength. The microwave irradiation of both flavonoid-based grape leaf extract and yarns up to 4 min, followed by dyeing, has given improved color yield up to a K/S value of 5.38. Metal mordants and bio-mordants were analyzed to improve dye fixation and sustainability. The pretreatment of yarn with Fe²⁺-salt, post-treatment with Al³⁺-salt, and addition of tannic acid during the dyeing process improved the color strength and dye fixation. Furthermore, the addition of red sumac extract during the dyeing of yarns and the pretreatment of yarn with myrobalan as bio-mordants increased the color depth. The colorfastness rating shows that mordanting has improved color stability and has offered maximum resistance to color fading. It is concluded that agro-waste valorization, statistical modeling coupled with radiation treatment, has not only added value in process optimization but also mordanting in the coloring of yarn with grape leaf extract has valorized the green dyeing.