Analyses of Adsorption Kinetics Using a Stirred‐Flow Chamber: II. Potassium‐Calcium Exchange on Clay Minerals

Potassium‐calcium adsorption kinetics on a Llano vermiculite and an Arizona montmorillonite were studied using a stirred‐flow technique. Various experiments were conducted to distinguish between (i) instantaneous equilibrium and time‐dependent reactions, and (ii) solution‐concentration‐dependent kinetic models vs. those that are independent of solution concentration. These experiments included varying the flow rate and influent concentration and stopping the flow for a period of time. It was found that K‐Ca exchange on montmorillonite was too rapid to be measured with the stirred‐flow technique, while exchange rates on vermiculite could be ascertained. Adsorption kinetic parameters should be included in transport models to more accurately predict the fate of ions in soils dominated by vermiculitic and micaceous clay minerals.