Adsorption of heavy metals from mining effluents using honeydew peels activated carbon; isotherm, kinetic and column studies

Abstract

In the current work, a new honeydew melon peels activated carbon (HDP-AC) with sulfuric acid (ACS) and phosphoric acid (ACP) was introduced as adsorbent for removing Cr3+ and Zn2+ from wastewater. The optimal adsorption of Cr3+ ions was recorded at pH 4.5 with 0.1 g adsorbent and 1000 mg/L of initial metal concentrations, while was at pH 5.5, 0.1 g adsorbent, 400 mg/L of initial Zn2+ concentrations, and after 40 minutes. The experimental data for both metals were noted fitted to the Langmuir adsorption isotherm. The highest adsorption capacity was 909.09 mg Cr3+ g−1 of ACS or ACP, while was 322.58 and 333.33 mg Zn2+ g−1 for of ACS or ACP, respectively. Pseudo-second order kinetics model fitted the adsorption of both metal ions. The breakthrough point in column adsorption was recorded at 70 minutes for Cr3+ and 100 minutes for Zn2+ and occurred at 60 versus 80, 55 versus 50 and 45 versus 50 minutes of first, second and third cycle removal of Cr3+ and Zn2+ respectively. These findings concluded that the column adsorption using ACP-packed column is more applicable for removing of heavy metals up to three adsorption cycles.