Solubility and stability of zeolites in aqueous solution: I. Analcime, Na-, and K-clinoptilolite

The solubilities of analcime and clinoptilolite were determined in dilute, weakly alkaline, aqueous solutions below 300 8C and at vapor-saturated pressures. Analcimes used in this study were from Mont St. Hilaire, Quebec (an1, Si/Al 5 2.02) and Wikieup, Arizona (an2, Si/Al 5 2.55); clinoptilolite samples were from Castle Creek, Idaho (Si/Al 5 4.50). The effects of alkali content (Na,K) on clinoptilolite solubility were determined by using cationexchanged varieties of the Castle Creek material (cp1, cp2). In neutral to weakly alkaline solutions, the dominant solubility-controlling reactions of these zeolites are 1 2 NaAlSi O ·H O(an ) 1 5H O(l) ↔ Na 1 Al(OH) 1 2Si(OH) (aq), 2 6 2 1 2 4 4 1 2 Na Al Si O ·H O(an ) 1 5H O(l) ↔ 0.85Na 1 0.85Al(OH) 1 2.15Si(OH) (aq), 0.85 0.85 2.15 6 2 2 2 4 4 1 2 Na Al Si O ·3.5H O(cp ) 1 8.5H O(l) ↔ 1.1Na 1 1.1Al(OH) 1 4.9Si(OH) (aq), 1.1 1.1 4.9 12 2 1 2 4 4