Thermodynamics of phosphate adsorption-desorption by alfisols, entisols, vertisols, and inceptisols

Adsorption and desorption of phosphorous (P) by four types of greek soils, Alfisols, Entisols, Vertisols, and Inceptisols, were the subject of the present investigation. These processes were studied under different conditions of initially added P concentration and at different temperatures. Analytical data (for all studied soils) show an increasing adsorption due to initially added P concentrations and increasing temperature. The desorption was also increased with the increasing of initially added P concentrations but was decreased with temperature increases, indicating that soil affinity for P was increased as temperature increased. Analytical data and results were explained and compained based on the physical properties of the soils. By using experimental data, equivalent constants, Keg (equivalence was reached between solid sample and P in the liquid phase), were calculated. The thermodynamic constants, Delta G(o), Delta H-o, and Delta S-o, were also estimated and discussed.