The various solutions of pH 1–7 were prepared by
addition of 2ml of dye from stock solutions and diluted to 100 ml
with buffer solutions of respective pH. The pHwas monitored by
pH meter (Model HM-7E). The absorbance of the dye solutions
was measured at various wavelengths and values of λmax were
obtained. The λmax for each dye is shown in Table 1. Weighed
amount (0.01 g) of activated charcoal in a flask containing 25 ml
dye solution was shaken in a water bath incubator (Hitachi BT-
47) at 298, 303, 308, 313 and 318 K. The solutions were filtered.
The absorption spectra were then recorded by a spectrophotometer
(Shimadzu UV-120-01) at their respective λmax of each
dye. The amount adsorbed, x/m (mg g−1) is plotted against the
equilibrium concentration, Cs (ppm) to obtain the adsorption
isotherms.