pH- and ionic concentration-dependence of monovalent cation retention by clays and clay minerals expected in soils

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Abstract
Yoshikawa (1) and Wada (2, 3) reported that monovalent cation retention by some ando soils and variable charge minerals was uniquely determined by pH—pC in equilibrium solutions, where pC denotes the negative logarithm of ionic concentration in the equilibrium solutions. In this study, monovalent cation retentions by some variable charge materials separated from soils were measured. The experimental data and the data taken from the literature were presented on ion retention-pH—pC diagrams and the one-to-one relationship between monovalent cation retention and pH - pC in equilibrium solution was verified for these minerals. The diagrams obtained also showed that the monovalent cation retention by these materials decreased with decreasing pH—pC and almost disappeared before the pH—pC value of 2 was attained.