Modelling cationic dyeing‐consideration of ionic and hydrophobic interactions in a modified Donnan approach

Abstract

A modified Donnan model has been derived, based on hydrophobic and ionic interactions between dyes and fibres. This model gives a good prediction of a cationic dye equilibrium sorption on an acrylic fibre under different dyeing conditions. The decrease in dye sorption with increasing salt concentration, followed by an increase in the dye sorption following further increase in the concentration of some salts (such as sulphates and phosphates), can be interpreted by this model. The study provides a quantitative approach to the dual functions of simple electrolytes during cationic dyeing, i.e. the competition of sorption sites with dyes through ionic interactions and the promotion of the dye sorption through hydrophobic interactions.