Cadmium and Lead Adsorption Capacities of Nigerian Ultisol Soil of Tropics

The study investigates the sorption of cadmium and lead (Pb) by Nsukka urban soils, a Nigeria soil classified as an ultisol soil of tropics. Laboratory batch technique was utilized to investigate the effect of pH, temperature, contact time, and concentration on the adsorption process. Results showed that adsorption efficiency of the soils for Cd2+ and Pb2+ increased with increase in pH, temperature, and contact time but decreased with increase in concentration. The data from adsorption study was fitted to the Langmuir, Freundlich and Temkin adsorption isotherms, and results revealed that Langmuir isotherm fitted most satisfactorily. On the basis of the obtained maximum adsorption capacity (q(max)) from the Langmuir model, the affinity of Cd-2+ and Pb2+ for the studied soil was Pb2+ > Cd2+. Pseudo-second order (r(2) = 0.995-0.999) best described the kinetics of the sorption process for the metal ions in the soil.