The sorption of RhB was performed by batch technique. Theamount of each adsorbent was fixed at 0.02 g, and the volume of RhB solution was fixed at 20 mL. According to the calibration curve of RhB, the max= 554 nm. The initial concentration of RhB solution was from 100 to 600 mg L−1, the adsorption was carried out atื293–323 K for 0.5–6 h. pH was adjusted by 0.1 M HCl or 0.1 M NaOH(the addition of acid or alkali in RhB solution was carried out whenwe investigated the effect of pH on adsorption). The amount of RhB adsorbed at time t (qt) was calculated by the equation