Ion-Exchange Properties of the Natural Zeolite Erionite1

Howard S. Sherry2
P. Q. Corporation, P.O. Box 258, Lafayette Hill, Pennsylvania 19444
1 Presented at the 1978 Clay Minerals Conference, Bloomington, Indiana.
2 Work done at Mobil Research and Development Corporation, Paulsboro, New Jersey 08066.
3 Ed. note. See Deffeyes, K. S. (1959) Erionite from Cenozoic tuffaceous sediments, central Nevada: Am. Mineral. 44, 501-509; Papke, K. G. (1972)Erionite and other associated zeolites in Nevada: Nev. Bur. Mines Geol. Bull. 79, 32 pp.

Abstract: Natural erionite was exhaustively ion exchanged with Na+ to give the anhydrous unit-cell composition (K1.9Na5.4Ca0.1Mg0.1)[(AlO2)7.4(SiO2)28.6]. A thermodynamic study of alkali and alkaline earth metal ion exchange in this zeolite was made and the selectivity series found to be Rb > Cs ≥ K > Ba > Sr > Ca > Na > Li. In all cases approximately two K+ ions per unit cell (probably those in the cancrinite cages) could not be replaced by conventional ion exchange. It was also found that two Na+ ions per unit cell are extremely difficult to replace with alkaline earth ions. It is believed that complete replacement of the approximately six Na+ cations in the two large cages per unit cell of erionite would result in a non-uniform, divalent cation population in these cages. A more stable anhydrous composition is (K2Ca2Na2)[(AlO2)8(SiO2)28] in which each large cage contains one Ca2* or other alkaline earth cation and one Na+ ion.

Key Words: Erionite • Ion exchange • Offretite • Selectivity • Zeolite • Zeolite T

Clays and Clay Minerals; June 1979 v. 27; no. 3; p. 231-237; DOI: 10.1346/CCMN.1979.0270309
© 1979, The Clay Minerals Society
Clay Minerals Society (www.clays.org)