THERMODYNAMICS OF POTASSIUM EXCHANGE IN CALCIUM BENTONITE (CA-B)

Potassium (K) sorption by calcium bentonite is influenced by temperature variations. In the present investigation, the kinetics of K adsorption from a solution to exchangeable sites of clay were studied using bentonite samples which had been saturated with calcium (Ca) in the form of CaCl2. Potassium adsorption was studied using a 100 mg K/L solution and equilibrated for 3, 5, 7, 10, 12,15, 20, 25, 30, and 35 minutes and 1, 2, 8, and 24 hours at 5, 20, 30, 40, and 50 degrees C. It was found that the K-Ca exchange is a kinetically controlled process at low temperatures although it is thermodynamically controlled at higher temperatures The reversible first order kinetic model was fitted on analytical results and was found to give a good description of K-Ca exchange process. Thermodynamic quantities, Delta G degrees, Delta H degrees, and Delta S degrees were also calculated.