Thermodynamic approach for copper specific and non-specific adsorption on calcareous soils [electronic resource].

Includes references.

Adsorption of copper was determined in batch experiments as function of pH, temperature, and the concentration of Cu2+ ions with and without 0.05 M NaCI using four Egyptian calcareous surface soils. The objectives of this study were to investigate the behavior of Cu2+ ions in calcareous soils, and to identify the difference between specific and non-specific adsorption and also to determine the thermodynamic aspects of Cu2+. Langmuir adsorption model was found to describe Cu2+ adsorption. The results indicated that the adsorption of Cu2+ at pH 7.5 was higher than at pH 55 and increased with increasing temperature (35°) as well. An attempt was made to measure the adsorption energy of Cu2+ ions. The standard free energy of adsorption (ΔG°) gave negative values indicating the spontaneous nature of the reaction. The enthalpy change (ΔH°) indicated that the adsorption of Cu2+ was endothemlic in nature. Finally, the adsorption of Cu2+ in calcareous soils was accompanied by positive entropy ΔS°) and the high values of the activation energy (E°a) indicated chemical reaction proceeded under the experimental conditions of this study.

Summary in Arabic.

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