Kinetics and Thermodynamics Studies of Cationic Dye Adsorption onto Carboxymethyl Cotton Fabric

Cotton fiber is a very rich natural polysaccharide material in nature, which is usually dyed with reactive dyes. However, a large number of salts remain in the dye bath waste, polluting the ecological environment. In this study, the salt-free dyeing of cationic dyes on carboxymethyl cotton fabric modified with sodium chloroacetate was carried out under the conditions of pH 7, initial dye concentration 0.5-10% owf, and liquor ratio 1:100. The results demonstrated that the cationic dyes were successfully adsorbed on the modified cotton fabric in the absence of salt, but the dyeing fastness was low. Furthermore, the adsorption thermodynamics and kinetics were investigated. The adsorption kinetics was found to follow the pseudo-second-order kinetic model, and the adsorption isotherm obtained was identified to be the Langmuir type. These results will help us to realize the salt-free dyeing of carboxymethyl modified cotton fabric in the future.