MEASUREMENT AND PREDICTION OF CA-NA ION-EXCHANGE EQUILIBRIUM IN MAXIMUM-ALUMINUM-P (MAP), A ZEOLITE WITH THE GIS FRAMEWORK TOPOLOGY

Ion-exchange equilibrium studies have been carried out on the system C a-Na-zeolite MAP (maximum aluminium P), and comparison made with those reported previously for Ca-Na-zeolite A. Over much of the exchange sy stem, zeolite MAP shows greater selectivity for calcium than does zeol ite 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 norm ality over at least the range 0.025 to 0.4 equiv. dm(-3), and predicti on procedures dependent on this requirement have been tested successfu lly.