An innovative, low-cost and environment-friendly approach by using a deep eutectic solvent as the water substitute to minimize waste in the textile industry and for better clothing performance

Abstract

With the increase in environmental protection awareness, the development of strategies to reduce effluent and lower the cost of the chemical reagents used in the textile wetting process has attracted wide attention. Wool is a representative natural protein fiber with good warmth retention and durability. However, owing to the presence of a dense and chemically inert scale layer on the surface, woolen fabric has poor dye absorption ability, and the wool dyeing process is generally accomplished under the conditions of high dye concentration, salt and an appropriate boiling temperature. Therefore, the development of a novel dyeing approach is important to overcome these limitations to some extent. In this study, a new water-free recyclable dyeing process that uses natural and an acidic deep eutectic solvent as the water-free medium was established for dyeing woolen fabric. The process could be completed by using only the dye and the deep eutectic solvent without other assistant reagents. The wool samples dyed in the acidic deep eutectic solvents had higher color strength (K/S value), similar colorfastness, satisfactory leveling properties, and acceptable mechanical behavior compared with those dyed using the conventional aqueous method. The deep eutectic solvent also could be used as a cleaning solvent to remove the excess dye adhering to the fabric surface after the dyeing process, and the dye-containing solvent could be reused at least 10 times. Thus, the cost, chemical reagent consumption, and waste production of the developed dyeing process were low. Several dyes and acidic hydrogen-bonding ligands of deep eutectic solvents were successfully applied to dyeing wool using this deep eutectic solvent dyeing method. This favorable result indicates that this method has satisfactory universality and the potential for industrial application. Together, the results indicate that this method meets the 3R principles of reducing waste, recycling resources and reusing. This investigation broadens the application field of deep eutectic solvents in the textile industry and can contribute to the further development of green approaches for textile dyeing and finishing.