Optimization of Copper, Lead and Nickel Ions Adsorption by Melia azedarach Activated Carbon: A Response Surface Methodology Approach

Diverse types of biomass have been reported to originate activated carbon and have been evaluated as heavy metals adsorbent to mitigate the environmental issue. In this study, Melia azedarach leaves and twigs were used as precursor for activated carbons preparation via molten salt synthesis using ZnCl₂ as activator at 500 °C. Melia azedarach leaves activated carbon (LAC) and Melia azedarach twigs activated carbon (TAC) were applied as adsorbent for Cu(II), Pb(II) and Ni(II) removal from aqueous medium. The central composite design was used to optimize the effect of adsorbent dosage, initial metal concentration and contact time on the adsorption process. The optimal Cu(II), Pb(II) and Ni(II) removal by LAC was found to be 98.52%, 98.58% and 89.17% correspondingly at 3.2 gL⁻¹, 2.3 gL⁻¹ and 3.90 gL⁻¹ adsorbent dosage, 54 ppm, 56 ppm and 56 ppm initial concentration and 140 min, 137 min and 158 min contact time. The optimal adsorption capacity for Cu(II), Pb(II) and Ni(II) by LAC was found to be 150.05 mgg⁻¹, 184.93 mgg⁻¹ and 158.558 mgg⁻¹, respectively, at 1.0 gL⁻¹ adsorbent dosage, 300 ppm, 297 ppm and 300 ppm respective initial concentration and 180 min, 178 min and 180 min respective contact time. By TAC, Cu(II), Pb(II) and Ni(II) removal efficiencies were 96.28%, 94.33% and 80.94%, respectively, for 3.944 gL⁻¹, 4 gL⁻¹ and 1.834 gL⁻¹ adsorbent dosage, 60 ppm, 50 ppm 55.60 ppm initial concentration and 153.809 min, 168 min and 179.893 min contact time. Cu(II), Pb(II) and Ni(II) adsorption capacities were determined to be 148.98 mgg⁻¹, 152.29 mgg⁻¹ and 226.855 mgg⁻¹, respectively, at 1.0 gL⁻¹ adsorbent dosage, 300 ppm initial concentration and 180 min, 180 min and 150.335 min contact time. Melia azedarach activated carbon has proven to be a valuable product for adsorbing heavy metals from aqueous medium.