Homovalent and Heterovalent Cation Exchange Equilibria in Soils with Variable Surface Charge

Abstract
Cation‐exchange equilibira involving K, Na, Ca, and Mg were studied with Chilean Dystrandepts.The K‐Na exchange and the Ca‐Mg exchange showed that K and Ca were preferentially adsorbed. Increased charge density through adsorption of phosphate resulted in a reduction in the selectivity for K in the K‐Na system. Phosphate adsorption had no apparent effect on the selectivity for Ca in the Ca‐Mg system.In heterovalent systems, these soils showed a perferential adsorption of the divalent cation. This selectivity was more pronounced at low equivalent concentration of the divalent cation. The selectivity for the divalent cation increased as the surface charge density was increased by phosphate adsorption.
Funding Information
  • Ford Foundation

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