Biosorption Studies of [Cd.sup.2+] and [Cr.sup.6+] from Aqueous Solution Using Cola-Nut Leaves as Low-Cost Biosorbent

Cola-nut leaf is an agricultural waste which was used in this research as biosorbent for the adsorption of [Cd.sup.2+]and [Cr.sup.6+] 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 [Cd.sup.2+]. The equilibrium sorption data was attained using the batch technique with increased pH (9) and increased adsorbent dose (1 g/25 [cm.sup.3] 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 [Cd.sup.2+] and [Cr.sup.6+] which could be utilized for industrial wastewater remediation.