Adsorption isotherm of Direct Sky Blue FF from AqueousAlcoholic Solutions

Abstract

Adsorption Isotherm of Direct Sky Blue FF on cellulosic substrate from aqueous alcoholic solutions has been determined.
All the isotherms, irrespective of the kind of alcohol and temperatures, are described as a sum of the Langmuir type and the distribution type;
Y=K₁SX/(1+K₁X)+K₂X
where Y and X are the concentration of dye on the substrate and that in solutionrespectvely, K₁, K₂ and S are the constants.
K₁ decreases and K₂/K₁ increases at 50° C with increasing the concentration of ethanol. Both K₂ and S show minimum values at 40 vol% ethanol solution.
The existence of an adsorption minimum at the concentration of 40 vol% which was pointed out in the previous paper, is also verifiable by the constants derived from the analysis of the absorption isotherms mentioned above.
When the alcohol which behaves more'effectively on dye uptake is applied, both K₂ and K₂/K₁ give larger values, but K1 gives a smaller one.
These analysesseem to support the supposition that the proportion of alcohol in aqueous solution influences the dye uptake in two ways.