Extremely Efficient Adsorption of Rhodamine B dye from Aqueous Solutions onto Modified Olive Stone Activated Carbon: Modelling and Optimization Studies

Abstract

In this study, the adsorption performances of ZnCl2, KOH and H3PO4 impregnated activated carbons derived from olive stones in the removal of Rhodamine B dye from aqueous solution were investigated. The equilibrium time was determined to be 6 hours, and the highest adsorption capacity was achieved by ZnCl2 impregnation (190.67 mg g-1) followed by KOH (118.26 mg g-1), H3PO4 (49.81 mg g-1), and crude olive stones (21.57 mg g-1) compared to the commercial powdered activated carbon (254.30 mg g-1). While different pH values (2-10) did not exhibit much effect, pH 4 was the most efficient one. The sorption capacity reached equilibrium at 200 mg L-1 of initial dye concentration. 0.01 gram of ZOSAC had 39% removal performance, whereas 0.05 gram was found to be sufficient for 100% removal. The presence of background ions enhanced the adsorption of Rhodamine B. Pseudo-second order model (R2=0.99) was most suitable for the experimental data among kinetic models. Redlich-Peterson (R2>0.98) model was found to be most suitable equilibrium model for all ACs. The temperature increase from 30 to 50℃ had an increasing effect on the adsorption capacity. It was also revealed that the adsorption was endothermic (∆H°=14.91 kJ mol-1) and thermodynamically favorable (∆G°<0) for ZOSAC. At the end of the fifth adsorption/desorption cycle, the removal efficiency was 94% and optimum adsorption conditions were determined as 45 ℃ and 252 mg L-1. As a result, ZOSAC was found to be the most efficient and reusable impregnated olive stone derived activated carbon in the Rhodamine B removal.