Equilibrium and Kinetic Studies of the Adsorption of Pb2+ and Ni2+ Ions from Aqueous Solution by the Use of Activated Locust Bean Husk (LBH)

The removal of Lead and Nickel ions from aqueous solution by adsorption onto activated locust bean husk was investigated in a well stirred batch reactor. Equilibrium and kinetic experiments were performed at various pH, temperature and contact time. The metal removal approached equilibrium within 70 min for lead and nickel. It was observed that removal of Pb2+ and Ni2+ by activated LBH had highest adsorption capacity at pH 6 and that the uptake of the selected heavy metal ions by activated LBH increases with increasing temperature. Kinetic studies carried out showed that the experimental adsorption capacities of Pb2+ and Ni2+ are 4.27 mg/g and 2.9 mg/g respectively. Their calculated adsorption capacities by using pseudo-first order model are 0.05 mg/g and 0.6 mg/g respectively, while that of pseudo- second order model are 4.48 mg/g and 3.57 mg/g respectively. The result obtained showed that the calculated adsorption capacities of all the metals by pseudo- second order model are closer to their respective experimentally determined adsorption capacities than those from pseudo- first order model. Hence, pseudo- second order adsorption model is more suitable to describe the adsorption kinetics of Pb2+ and Ni2+ by activated LBH.