POTASSIUM SORPTION BY CALCIUM-BENTONITE (CA-B)

The kinetics of Potassium adsorption from solution to exchangeable pha ses was investigated on bentonite samples which were first saturated w ith calcium in the form of CaCl2. Potassium adsorption time was evalua ted on Ca-saturated samples using 125, 150, 200 and 250 mugK/ml soluti ons, equilibrated for 10, 15, 20, 30, 35, 45, 60, 75, 80 and 120 minut es. Sample pH levels varied between 4.0 and 9.0. Equilibrium in potass ium exchange was reached faster in lower concentrations and higher pH values. Four mathematical models (first-order rate, parabolic diffusio n, Elovich and modified Freundlich equation) were used to describe pot assium sorption. Comparison of coefficients of determinations (r2), an d plots indicated that modified Freundlich and parabolic diffusion mod els provided the best fits of the adsorption data (r2 > 0.979). Consta nts for the Freundlich equation were estimated and the model was expre ssed as a function of pH.