A holistic approach in harnessing impregnated olive stone based activated carbon for Rhodamine B dye removal

This study explored the adsorption performances of ZnCl₂, KOH and H₃PO₄ impregnated activated carbons derived from olive stones for Rhodamine B dye removal from aqueous solutions. The equilibrium time and initial dye concentration were 6 h, and 200 mg L⁻¹, respectively with ZnCl₂ exhibiting the highest adsorption capacity (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). ZnCl₂ impregnated activated carbon (ZOSAC) demonstrated enhanced removal as the adsorbent amount increased and background ions facilitated adsorption. Pseudo-second order model (R² = 0.99) best represented the experimetal data among kinetic models. Redlich-Peterson (R² > 0.98) model was the most suitable equilibrium model for all ACs. Increasing the temperature from 30°C to 50°C enhanced adsorption capacity. Adsorption was determined to be 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 the optimal conditions were 45°C and 252 mg L⁻¹. ZOSAC emerged as the most efficient and reusable activated carbon for Rhodamine B removal.