Abstract
Distribution coefficient (K
d
) indicates the capability of a soil to retain a solute and consequently its distribution between solid and liquid phase. The purpose of this study was to determine copper (Cu) K
d
values of different soils to evaluate their ability to retain it and control its mobility and therefore availability. Eleven surface soil samples varying widely in their origin and properties were selected from Egypt and Greece for this study. Four of them were from Egypt representing the main soil orders: Entisols (developed on fluvial, lacustrine, and sandy marine deposits) and Aridisols (calcareous deposits). The other seven soils were from Greece belonging to the orders Entisols, Alfisols, Vertisols, Mollisols, and Histisols. Copper (Cu) distribution coefficient values were obtained by batch equilibrium experiments from which adsorption isotherms were prepared.
The results showed that the Freundlich model satisfactorily described Cu sorption. Clayey and alkaline soils exhibited much greater Cu sorption capacity than the sandy and acid soils. Copper distribution coefficients values differed significantly between the studied soil orders and ranged from 80.9 l kg
−1
in the acid Greek Alfisol to 7502.4 l kg
−1
in the Egyptian lacustrine Entisol and were significantly correlated with clay content, cation exchange capacity, organic matter, total free silica, and amorphous iron (Fe), aluminum (Al), silicon (Si), and manganese (Mn) oxides. Adsorption of Cu in the studied variable charge red soils was pH dependent. Values of K
d
decreased clearly as the concentration of the included cation increased in the test solution.