Title: Cation Selectivity in Sodium‐Calcium, Sodium‐Magnesium, and Calcium‐Magnesium Exchange on Wyoming Bentonite at 298 K
Abstract:Abstract Exchange isotherms were prepared for Na + in Na + →Ca 2+ and Na + →Mg 2+ exchange reactions, and for Mg 2+ in Na + →Mg 2+ exchange reactions, at 298 K on Wyoming bentonite suspended in a 0.05...Abstract Exchange isotherms were prepared for Na + in Na + →Ca 2+ and Na + →Mg 2+ exchange reactions, and for Mg 2+ in Na + →Mg 2+ exchange reactions, at 298 K on Wyoming bentonite suspended in a 0.05 M perchlorate background. These isotherms were essentially congruent with the appropriate thermodynamic nonpreference exchange isotherms. It was concluded from this fact that there is essentially no difference in the affinity of montmorillonite clay for Ca 2+ vs. Mg 2+ . However, exchange isotherms prepared for Na + in Na(I) → Ca(II) and Na(I) → Mg(II) exchange, as well as published ones for Mg(II) in Ca(II) → Mg(II) exchange on montmorillonite suspended in a 0.05 M chloride background consistently indicate a slight preference on the clay for Ca(II) over Mg(II). This preference for Ca(II) is concluded to be the result of the formation of CaCl + complexes, which are more stable thermodynamically and have a greater affinity for the clay than MgCl + complexes.Read More