INVESTIGATION INTO AN ECO-FRIENDLY REACTIVE DYEING PROCESS OF COTTON FABRICS USING AN ETHANOL-WATER MIXTURE THROUGH DESIGN OF EXPERIMENT

Textile industry professionals are unanimous that there is a great need to develop environmentally sustainable methods of cotton dyeing. Among various problems related to conventional dyeing, some of the main problems consist in the large volumes of discharge effluent with a high concentration of salt and their impact on the environment. This investigation explores the use of ethanol as a solvent in the reactive dyeing of cotton fabric, to reduce the concentration of salt and the volume of water used. The dyeing process employed a 90:10 (v/v) ethanol-water mixture. Time and temperature were varied periodically to improve the degree of exhaustion, and the effects of time, temperature and salt content were studied and compared with conventional reactive dyeing. It was observed that the colour strength of solvent-assisted reactive dyeing is comparable to the conventional process. The dyed sample under the optimum condition had good wash fastness, both in terms of shade change and staining, and its dry crocking fastnesses were found similar or acceptable in comparison with the water-dyed sample. However, all the samples of the solvent-assisted reactive dyeing process have better wet crocking fastnesses compared to the conventional reactive dyeing process. The process parameters of eco-friendly reactive dyeing have been optimised using the composite desirability function. The optimal process parameters for the solvent-assisted reactive dyeing process were found to be 60 minutes of dyeing at 80 °C with 20 g/L of salt.