Effect of time and temperature on potassium adsorption-desorption and thermodynamic parameters for some soils in Duhok governorate

الملخص EN

Soil samples were taken from the surface layer of Kanimasee, Domiz and Sarsang locations /Duhok governorate – Iraq, to determine adsorption, desorption, thermodynamic and pseudother-modynamic parameters of K using Gibbs' and Eyring's reaction rate theories.

The result demonstrated an increase in adsorbed and desorbed potassium to a limited value with increasing time and temperature from 274 K°, 283K ° , 298K ° and 322 K° in all studied soils.

Kanimasee soil exhibit high adsorption for K.

while high quantity of desorption found in Sarsang soil (2183 ، 11506) mg.kg-1 at 322 K° , and the cumulative desorbed K was lower than adsorbed K.

The adsorption rate coefficient Ka and desorption Kd values increased with increasing temperature degree, and the Kd values which were lower than the Ka values.

High value of Ka in Domiz soil ranged between (0.267 ، 0.287) hour-1 .

Activation energy of adsorption Ea and desorption Ed affected by total CaCO3 and active CaCO3 content.

The Ea values were less than the Ed values, indicating that high amount of energy was needed to desorb potassium than to adsorb.

The free energy (∆G°) of exchanged potassium values was negative, which indicates that the reaction are spontaneous, its values ranged between (-4.891، -5.434), (- 3.935، -4.876) and (-2.848 ، -4.931) Kjoule.

mol-1 for Kanimasee, Domiz and Sarsang soils respectively.

The potassium enthalpy (∆H°) values was negative (-5.654), (-9.872) and (-15.141) Kjoule.

mol-1 for Kanimasee, Domiz and Sarsang soils respectively.

The activation enthalpy of potassium from adsorption (∆Ha ‡) and desorption (∆Hd ‡) decreases with increasing temperature.

High value of entropy (ΔS°) initiate in Kanimasee soil, in general the (ΔS°) values of the K in studied soils increased with increasing temperature.