Biosorption Studies of Cd2+ and Cr6+ from Aqueous Solution Using Cola-Nut Leaves as Low-Cost Biosorbent

Abstract

Cola-nut leaf is an agricultural waste which was used in this research as biosorbent for the adsorption of Cd2+and Cr6+ from aqueous solutions. The leaves of cola nut were modified using 0.1 M HCl. Modified cola nut leaves biosorbent showed slightly higher percentage sorption than the unmodified leaves, for both heavy metals with increasing contact time, having greater affinity for Cd2+. The equilibrium sorption data was attained using the batch technique with increased pH (9) and increased adsorbent dose (1 g/25 cm3 of adsorbate) and initial metal concentration. The functional group of cola nut leaves before and after adsorption was determined using Fourier Transform Infrared Spectroscopy (FTIR). Kinetics data were best fitted to a pseudo-second-order model. Equilibrium data were better described by the Temkin isotherm model with a multilayer adsorption capacity. The study showed that leaves of cola nut are a promising biosorbent for Cd2+ and Cr6+ which could be utilized for industrial wastewater remediation.