The effect of temperature on the adsorption of lac dye on
cotton was investigated. It was found that a higher dyeing temperature
resulted in higher initial dye adsorption rate (hi) on
cotton before equilibrium as shown in Fig. 1. These results
are similar to those observed for lac dyeing of silk in our previous
work [12]. The mobility of the large dye ions would be
increased at higher temperature and subsequently the rates of
dyeing would be enhanced. A similar observation was also reported
in the study on the adsorption of a basic dye on crosslinked
cotton [17]. At the equilibrium time, the dye adsorbed
by the cotton decreased with increasing temperature, indicating
an exothermic process. As can be observed from
Fig. 1(a), the time required to reach equilibrium was shorter
at higher dyeing temperatures, i.e., 120, 60 and 5 min at 10,
30 and 60 C, respectively.
The dyeing condition of pH 3.0, initial dye concentration of
480 10 mg/L and MLR of 1:100 was subsequently used to
study the adsorption kinetics of lac dye on cotton.