The Influence of Different Electrolytes on the Interaction of Chlorazol Sky Blue FF with the Cotton Fiber Surface in Aqueous Solutions

Abstract

Investigations were carried out to study the adsorption of Chlorazol Sky Blue FF on cotton fiber from aqueous solutions of 0.1 N LiCl, NaCl, KCl, RbCl, and CsCl. The dye uptake both at 50° and 60° increased markedly with increasing size of the alkali metal cation. The equilibrium dye adsorption could be described by a Langmuir-type equation. The calculated standard affinity of dye adsorption showed a fairly constant value, but the exothermic heat of dyeing and the entropy of dyeing, calculated from the individual isotherms, increased as the dye adsorption increased in the presence of either higher electrolyte concentrations or equivalent concentrations of alkali metal cations of larger size. Possible changes in the orientation of adsorbed dye ions on the cellulose surface can account for the increased -Δ H° and - ΔS° values. It is pointed out that, apart from the usual well known effects of electrolyte cations, an ,important contributory factor to the adsorption process arises from the disturbance caused by the cations to the structure of water hydrogen-bonded to the cellulose surface and "iceberg" water around the hydrophobic parts of dye molecules. This effect, which will increase with the size of the alkali metal cation, explains the results adequately.