Kinetics of Wool Dyeing with Acid Dyes

Abstract

Studies of the thermodynamics and kinetics of dyeing over the past 60-70 years have not resulted in complete acceptance for one mechanism for the dyeing process. Contrary to the two existing explanations of wool-dye isotherm data (the Gilbert-Rideal and Donnan theories), the uptake of the acid dye used in this study conforms to the law of mass action. In addition, although it has generally been accepted that the kinetics of wool dyeing is diffusion controlled, the uptake rate of the acid dye used in this study can be modeled by a second-order rate expression based on the formation of a protein-dye complex as the rate determining step. The mechanism developed from this study involves the dye and other anions present in the dye solution interacting independently with the wool, rather than the dye displacing smaller anions in a strict ion exchange manner.