Sodium Adsorption On Calcined Clays and Zeolites.

Calcined clays are commonly added to golf courses to increase the water holding capacity of the soil.  An initial characterization of a commercially available calcined clay shows that as pH increases, sodium adsorption on the clay increases sharply.  Recent research into the effect of nanopores on adsorption has shown that nanopores can strongly influence retention of cations presumably by forcing them to shed their hydration spheres.  This Hydrated Ion Size Exclusion (HISE) process can cause ions such as sodium, which usually adsorb weakly, to instead be retained quite strongly within the nanopore channels.  Experiments evaluating ion exchange of sodium adsorbed on three zeolite minerals with various nanopore dimensions using Mg²⁺, K⁺, and Ba²⁺ shows the potential to remove sodium ions adsorbed within nanopores by replacing them with other cations also capable of exploiting the HISE effect.  A study of ion exchange on calcined clays shows that introduction of high enough concentrations of competing cations can affect the amount of sodium retained and ameliorate sodic conditions to some degree.