Enhanced Retention of Sodium Ions in Constrained Clay Environments.

Sodic soils are a serious problem worldwide and understanding the retention mechanisms of sodium in these soils will help us understand how to manage them. Sodic soils are high in clay content. We studied the retention of sodium ions by montmorillonite clay minerals in two different environments, namely: batch and column experiments. The column experiments showed a significant increase in sodium retention, which suggests that the external physical pressures applied to the clay minerals will impact the chemical retention processes. Specifically, we propose that the nanopore inner-sphere enhancement (NISE) effect is responsible for the increased retention strength of clays for sodium ions. The NISE effect is induced by the external compression pressures applied to the clay. We believe that the retention of sodium by sodic soils are also impacted by clay compression-induced NISE effects.