A comparative study on some thermodynamic approaches for predicting the cation exchange isotherms in binary systemsl [electronic resource].

Includes references.

The current study aimed to assess the applicability of some exchange isotherm approaches, i.e., Gains-Thomas (equivalent fraction) and Argersinger-Vanselow (mole fraction) for descriptiag the cation adsorption ia soil system.To achieve this target, an experimeat was carreid out on the exchange isotherms for binary systems ofNa-Ca and K-Ca in an aggregated sandy clay loam soil using batch and miscible-displacement techniques. The obtained results revealed that the selectivity coefficient of Na-Ca exchaage isotherm, as calculated using Gains-Thomas (KGTNa), approximately constant at all the studied solution conceatrations, except that those of low Na:Ca ratios, which showed slightly high values. Whereas, KvNa of Argersinger-Vanselow exhibited gradually decrease with increasing the Na:Ca ratios. As for the calculated true exchange constant, using the integral equation of the conventional thermodynamic approaches or Rothmund-Kornfeld formulation, that take into consideration the activity of adsorbed phase, appeared approximately constant values for the two conventions at all the studied solution concentrations.

Summary in Arabic.

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