CATION-EXCHANGE ISOTHERMS OBTAINED WITH BATCH AND MISCIBLE-DISPLACEMENT TECHNIQUES

An improved miscible-displacement technique for measuring adsorption isotherms is developed and its results compared with those from a standard batch method for cation exchange in a strongly aggregated, heavy clay soil. The new technique is based on destructive sampling of unsteady, unsaturated flow experiments and an improved method for simultaneously measuring solution- and exchangeable-cation concentrations. Results confirm that this technique is suitable for measuring exchange isotherms, and also permit some observations to be made about the rate of approach to equilibrium of ion-exchange reactions in aggregated soils and the suitability of equilibrium exchange isotherms for application to natural flow regimes. -from Authors