Comparative Adsorption Study of Cr(VI) and Mn(II) Ions Using Raw and Chemically Activated Pomegranate Peel–Derived Carbon

Abstract

Chromium and Manganese ions are considered non-essential and highly toxic elements in drinking water. In this study, the adsorption of these ions from water was examined using pomegranate peel (PP) and activated carbon obtained from pomegranate peel (ACPP) as adsorbents. Pomegranate peel powder was chemically modified with phosphoric acid (H₃PO₄) to enhance the adsorption characteristics of activated carbon. A batch adsorption study was conducted to assess the effect of the solution’s pH, temperature and contact time on adsorbent removal effectiveness. This adsorption isotherms study revealed that the adsorption of Mn(II) and Cr(VI) onto PP and ACPP follows the Langmuir isotherm with a correlation coefficient of more than 0.95. The maximum monolayer adsorption capacities of ACPP as well as PP were found to be 142.86 and 100.52 mg/g as well as 90.91 and 55.56 mg/g for Mn(II) and Cr(VI), respectively. The adsorption kinetics were investigated using the pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The correlation coefficient indicated that the adsorption process adhered to pseudo-second-order kinetics. Moreover, the concurrence between the measured and computed values of q_e indicated a closely aligned adsorption equilibrium. The findings suggest that PP could be a cost-effective and promising adsorbent for effectively removing Cr(VI) and Mn(II).