ABSTRACT
Zn2+ mobility and bioavailability depend on soil characteristics such as composition, surface charge, pH and redox conditions which can either be adsorbed, leached or absorbed by plants. Adsorption isotherms and kinetics are used to describe the equilibrium relationship between the amount of adsorbed and dissolved. The study aimed at investigating the model based isotherms and kinetics study of Zn2+ sorption unto unmodified coconut husk.
The study was conducted using coconut husk samples collected from AGR 305 farm, Faculty of Agriculture, University of Benin. The Zn2+ sorption capacities were determined by equilibrating 0.2 g, 0.4 g, 0.6 g, 0.8 g, 1.0 g and 1.2 g of coconut husk adsorbent in 100 ml Zn2+ solution concentration various concentration of Zn2+ as ZnSO4.7H2O at constant temperature. Zn2+ sorption kinetics was determined by equilibrating 1 g coconut husk adsorbent in 100 ml Zn 2+ solution containing 100 mg L-1 Zn2+. Zn2+ sorption data were fitted to Freundlich, Langmuir and Temkin models. While Zn2+ sorption kinetics data were printed to Pseudo-second-order, Intra-particle diffusion and Elovich kinetics model.
Results revealed that the amount of Zn2+ adsorbed increased with increase in Zn2+ concentration. The Temkin model expressed Zn2+ sorption capacity better considering the R2 values of 0.99, 0.99, 0.99, 0.99, 1.00 and 1.00 for 0.2 g, 0.4 g, 0.6 g, 0.8 g, 1.0 g and 1.2 g respectively. While the Pseudo-second-order kinetics model express Zn2+ sorption kinetics model better than the other models used considering the R2 values of > 0.99. Proper Zn2+ management is required to reduce contamination of soil and water.
