Measurement and prediction of Ca–Na ion-exchange equilibrium in maximum aluminium P (MAP), a zeolite with the GIS framework topology

Ion-exchange equilibrium studies have been carried out on the system Ca–Na-zeolite MAP (maximum aluminium P), and comparison made with those reported previously for Ca–Na-zeolite A. Over much of the exchange system, zeolite MAP shows greater selectivity for calcium than does zeolite A. The high selectivity for calcium shown by MAP and the unusual Z-shaped selectivity plot are attributed to the formation of coexisting sodium- and calcium-rich zeolite phases. The selectivity coefficient K G at any given calcium loading is invariant with solution total normality over at least the range 0.025 to 0.4 equiv. dm -3 , and prediction procedures dependent on this requirement have been tested successfully.