Adsorption experiments were carried out by using the batch
technique at various temperatures. To determine the optimum pH
value where the maximum adsorption was accomplished, 50 mL
dye solutions of various concentrations were treated with 0.025 g
adsorbent in the 100 mL Erlenmeyer flasks and then the pH was
carefully adjusted between 1.5 and 9 by using NaOH or HCl
solution. The solutions were stirred for 60 min by using a magnetic
stirrer at a constant temperature of 20 8C maintained by a
thermostatic water bath. Then, the solution was filtered, and the
concentration of the dye in the solution was determined by means
of UV–vis spectrophotometer.