Zinc sorption of soils of varying lithologies in a humid tropical environment
Zinc sorption capacity of soils of different parent materials in Imo state, southeastern, Nigeria was evaluated by equilibrating 2 g soil with 25 ml ZnSO4 solution containing graded zinc concentrations (0, 25, 50 and 100 mg/L) with KCl as the background electrolyte and sorbed zinc determined. Sorbed zinc was fitted to the Langmuir, Freundlich and Temkin isotherms and sorption maximum (b), affinity constant (k), bonding energy (n), distribution coefficient (Kf) and equilibrium zinc concentration (EPCo) determined. Sorption maximum was higher in shale, while the reverse was the case for the affinity constant. Zinc sorption capacity using sorption maximum followed the order coastal plain sands<alluvium<shale and the affinity constant followed the order shale<coastal plain sands<alluvium. Sorption maximum, affinity, bonding energy, distribution coefficient, equilibrium zinc concentration significantly correlated with Effective cation exchange capacity (ECEC), phosphorus (P), clay content and sand.