Thermodynamics and kinetics of cashmere dyeing with metal complex dye

Abstract

The optimal condition, kinetics and thermodynamics of adsorption of the metal complex dye onto cashmere fibre have been studied in order to evaluate the improvement of cashmere qualities under industrial dyeing conditions with metal complex dye. The optimal conditions for dyeing cashmere fibre are obtained at 85°C temperature, 2-13% initial dye concentration, 3.5 <em>p</em>H and 50 min treatment time. By reducing the temperature and operating time, qualities of cashmere fibre such as luxury and softness improve, and damage to fibres decreases significantly. As a consequence, opportunities for enhancement of cashmere product quality and industrial efficiency due to mild industrial conditions and lower energy needs are attained. The adsorption kinetics of metal complex dye onto cashmere fibre follow a pseudo-second-order kinetic model with an activation energy of 77.33 kJ·mol^-1. The Langmuir isotherm is found the best model for dyeing adsorption onto cashmere fibre. On the basis of thermodynamics, kinetics and diffusion models, both adsorption and diffusion are involved in the process of dyeing cashmere, and an electrostatic attraction between dyeing molecules and cashmere fibre occurs.