Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012.
1Present address: Indian Institute of Soil Science, Berasia Road, Bhopal, Madhya Pradesh, 462038.
An experiment was conducted to measure the thermodynamic parameters of zinc sorption in soils to understand the mechanism of zinc sorption in soil. Soil samples were incubated with 0.01 M calcium nitrate solution containing graded concentrations of Zn (0 to 20 mg L−1) at 25°C and 40°C for 7 days. The thermodynamic parameters viz. K°, ΔG°, ΔH°, ΔS° were determined for this process by using sorption data at two different temperatures and surface area of soils. The fit of the sorption data was tested both in Freundlich and Langmuir isotherms, and could be described satisfactorily by Freundlich equation only. The results showed that CEC, organic matter, pH and clay content were the main contributors to Zn sorption in these soils. Zinc sorption and also the values of thermodynamic parameters e.g. K°, ΔG°, ΔH°, and ΔS°, increased at elevated temperature. The zinc sorption in the soils is endothermic and spontaneous.
Sorption, Zinc, thermodynamics, soil, Freundlich equation
