Pakistan Research Repository

Chemistry of Phosphate Adsorption in Soil

Khan, Fazlullah (1985) Chemistry of Phosphate Adsorption in Soil. PhD thesis, University of Peshawar, Peshawar .



The sorption/dosorption of phosphate in soils and calcite is studied in different electrolyte solutions and at different temperatures. Soil being the adsorbent is analysed for its physico-chemical properties. The various phosphate fractions and the available phosphate are determined and correlated with the soil properties. The Langmuir and Dubinin - Radushkevich adsorption equations are applicable to the equilibrium sorption data. Para meters like adsorption maximum and energy of adsorption are determined the values of which depend upon the cations and anions present in. the soil solution, temperature of the concentration of the electrolyte and physico chemical properties of the soils. Kinetics of phosphate sorption show that the process follows two steps first order kinetics and the data is also found to fit the Elovich type equation. From the rate constants, the activation energy, enthalpy of activation, entropy of activation, free energy of activation and energy of desorption are calculated. Desorption of the added phosphate in different electrolyte solutions is also of the first. order. desorption by the additional increments of resin Amberlite IRA 400 (CI-) is accompanied by the increase in solution concentration of Ca2+ , K+, Na+ and H+, indicating Us. dissolution of some inorganic phosphate compound. Applying the solubility method to the desorption data confirms the presence of the dicalcium phosphate in the soils. The phosphate compound formed as a result of the sorption of phosphate in soils and calcite is characterized by the solubility phase diagram method. In the range of phosphate addition of 0-100 mg/5 g of soil, dicalcium phosphate dihydrate is formed. Infrared spectra of the calcite treated with phosphate indicate which are move: pronounced at high concentrations and longer periods of incubation. Ball like growths appear on the surface of the calcite in scanning electron micrographs showing phosphate precipitation at high concentrations. Electron probe microanalysis of the precipitated calcium phosphate shows that hydroxy apatite is the reaction product of the sorption process.

Item Type:Thesis (PhD)
Uncontrolled Keywords:Chemistry, Phosphate, Adsorption, Soil, properties, desorption, physico chemical
Subjects:Physical Sciences (f) > Chemistry(f2)
ID Code:6786
Deposited By:Mr. Javed Memon
Deposited On:26 Jul 2011 10:32
Last Modified:26 Jul 2011 10:32

Repository Staff Only: item control page