Utilization of agricultural waste adsorbent for the removal of lead ions from aqueous solutions

Abstract

In this study, a performance evaluation of an aluminium oxide modified onion skin waste (Al2O3/OSW) for the removal of heavy metal ions (Pb2+ and Cd2+) from aqueous solution was investigated under batch mode adsorption. The surface morphology, elemental composition, functional groups, textural characteristics and surface charge of the as-made Al2O3/OSW adsorbent were examined using SEM, EDX, FTIR, BET surface area and pHpzc techniques, respectively. The effects of initial cations concentration, contact time, adsorbent dosage, and pH on adsorption of Pb2+ and Cd2+ onto Al2O3/OSW were studied. The adsorption data obtained were evaluated by various adsorption isotherm and kinetic models. Results obtained showed that maximum removal percentages of Pb2+ and Cd2+ were 91.23 and 94.10%, respectively, at the optimum Al2O3/OSW dosage of 1.4 g, contact time of 180 min and aqueous solution pH of 6.0. The isotherm and kinetic studies showed a multilayer adsorbate-adsorbent system with the dominance of the chemisorption mechanism. The study concluded that onion skin waste is a viable, cheap and very effective alternative for removing heavy metal ions from water/wastewater.