It was found that the uptake of the dye decreased with increasing
temperature, thereby indicating that the process is an exothermic
one. This is in agreement with the experimental results
of the adsorption of lac dye on cotton without pH control by
Janhom et al. [14].
When 1/qe was plotted against 1/Ce according to Eq. (3),
the Langmuir model fitted the experimental data very well
with high correlation coefficients (R2O0.98). The values of
the Langmuir constants Q and b were calculated from the intercepts
and slopes of different straight lines, respectively, at
different temperatures. The calculated results are reported in
Table 1. It was found that Q values decreased with increasing
temperature. Similar observations were reported for the adsorption
of lac dye on silk