The adsorption of direct dyes on cellulose

Abstract

The dyeing of cellulose with direct dyes has been studied in detail by Neale and his collaborators, and a quantitative theory to account for the effect of dye and electrolyte concentration on the adsorption equilibrium has been developed by Hanson, Neale & Stringfellow (1935). More recently, a slightly different theory has been described by Willis, Warwicker, Standing & Urquhart (1945), supported by a very full examination of the adsorption of Chrysophenine G on cellophane sheet. The two theories are based on common postulates and differ mainly in the mathematical development and the simplifying assumptions which are adopted. Both assume that the direct dyes exist in solution as fully dissociated salts of the type Na z D, and that of all the ions present only the dye anions are specifically adsorbed at the cellulose/water interface. The distribution of all other ions is determined by the need for electrical neutrality in any finite volume of the system. Hanson et al . divide the dyeing system into two parts, namely, the aqueous solution contained within the fibre and the external solution, and proceed to apply the laws of membrane equilibrium to the distribution of ions between these two parts of the solution.