3.1.3. The effect of contact time and initial dye
concentration on the adsorption of lac dye on cotton
The adsorption capacity of lac dye on cotton was a function
of the initial dye concentration. As expected, the amount of the
dye adsorbed on cotton increased with an increase in the initial
concentration of dye solution. This is due to the increase in the
driving force of the concentration gradient with the higher initial
dye concentration [18]. Nearly 60 min were required for
the equilibrium adsorption at initial dye concentrations of
137, 272 and 480 mg/L. The maximum of the dye adsorbed
per gram of cotton at initial dye concentration of 480 mg/L
was 5.00 mg/g cotton. The contact time for the adsorption isotherm
study of lac dye of pretreated and untreated cotton with
chitosan at pH 3.0 was fixed at 3 and 2 h, respectively.
The optimal conditions obtained from this study at pH 3.0
and MLR 1:100 were subsequently used to study the adsorption
isotherm of lac dye on cotton.