KINETICS OF POTASSIUM ADSORPTION BY ENTISOLS OF GREECE

The kinetics of potassium adsorption from solution to exchangeable phases was investigated on Entisols Herothern from central Greece. Potassium adsorption with time was evaluated on Ca-saturated samples using 3.5, 16.8, 67.5 and 86.0 ppm initial concentrations and pH levels of 5.0, 6.0, 7.0, 8.0 and 9.0. Four mathematical models (first-order rate, parabolic diffusion, power function and Elovich) were used to describe cumulative K adsorption. Comparisons of coefficients of determination (r2) indicated that the power function, Elovich and first-order rate models adequately described cumulative K adsorption, whereas the parabolic diffusion model was less successful. Constants A and B were calculated from reaction time vs. quantity of K adsorbed using the four mathematical models. From all four tested models only the power function and first-order models were found to be transformed to pH-dependent forms.