Effect of metal ion concentration on the biosorption of Pb2+ and Cd2+ by Caladium bicolor (wild cocoyam)

The influence of initial metal ion concentration of the batch sorption of Pb2+ and Cd2+ onto a low-cost biosorbent was investigated. The experimental results were analysed in terms of Langmuir and Freundlich isotherms. According to the evaluation using Langmuir equation, the monolayer sorption capacity obtained were 49.53 and 65.50 mM/g for Pb2+ and Cd2+, respectively The data further showed that, sorption of the two divalent metals onto the biomass increased with increase in initial metal ion concentration until monolayer coverage is attained. The thermodynamic assessment of the metal ion – Caladium bicolor biomass system indicates the feasibility and spontaneous nature of the process and ΔGo was evaluated as ranging from –4.55 to –6.63 KJ mol-1 and –4.02 to –6.09 KJ mol- for Pb2+ and Cd2+ sorption, respectively. The order of magnitude of the ΔGo values indicates an ion-exchange physisorption process.African Journal of Biotechnology Vol. 4 (2), pp. 191-196, 200