THE SORPTION ISOTHERMS OF POTASSIUM
The one- and two-surface Langmuir, the Freundlich and the Temkin isotherms were fitted to potassium sorption data for Alfisol Haploxeralf at pH range of 4.0 to 8.0. Each was found to describe potassium sorption data with comparable success, with the Freundlich model being slightly superior. The effect of pH on the potassium adsorption was studied and Langmuir, Freundlich and Temkin isotherms were converted to pH-dependent forms. The amount of adsorbed potassium increased as pH and initial concentration increased. From the Landmuir isotherm, the maximum amount (Xm) that can be sorbed in a monolayer was estimated. It is noteworthy that the maximum amount (Xm) of K increases by increasing pH. The four isotherms were transformed into pH-dependent forms.