POTASSIUM SORPTION BY CALCIUM-BENTONITE (CA-B)

The kinetics of Potassium adsorption from solution to exchangeable phases was investigated on bentonite samples which were first saturated with calcium in the form of CaCl2. Potassium adsorption time was evaluated on Ca-saturated samples using 125, 150, 200 and 250 mugK/ml solutions, equilibrated for 10, 15, 20, 30, 35, 45, 60, 75, 80 and 120 minutes. Sample pH levels varied between 4.0 and 9.0. Equilibrium in potassium exchange was reached faster in lower concentrations and higher pH values. Four mathematical models (first-order rate, parabolic diffusion, Elovich and modified Freundlich equation) were used to describe potassium sorption. Comparison of coefficients of determinations (r2), and plots indicated that modified Freundlich and parabolic diffusion models provided the best fits of the adsorption data (r2 > 0.979). Constants for the Freundlich equation were estimated and the model was expressed as a function of pH.