Exploring Different Methods for Eco-Friendly Wool Dyeing with Natural Carmine Dye and Waste Wool Hydrolysates

Waste wool hydrolysates (WWHs), a by-product originating from the alkaline hydrolysis of waste wool, are recovered and employed as auxiliaries in wool dyeing. In view of an eco-friendly dyeing procedure, a natural dye, Carmine, is selected to dye wool fabrics. Different methodologies for performing the dyeing process are described. In the first procedure, the wool fabrics are pretreated with a water suspension of the WWHs at room temperature, left overnight, and then cured at 180 °C. In the second procedure, the wool fabrics are immersed in the WWH's suspension at 100 °C, dried in an oven, and subsequently dyed through the exhaustion method. In the last procedure, the WWHs are added directly to the dyeing liquor. Dye exhaustion, color coordinates, and K/S are measured to evaluate the dyeing efficiency. The dyed fabrics are also characterized in terms of thermal, chemical, mechanical and morphological properties. The results demonstrate that the WWHs are efficient alternatives to metal-based mordants in assisting wool dyeing with Carmine dye. The evidence of non-significant damages to fabrics as a consequence of the chosen treatment conditions further supports the possibility of WWH valorization in textile industries as a by-product that otherwise would represent a waste to dispose of.