Interaction between organic vapors and clinoptilolite–mordenite rich tuffs in parent, decationized, and lead exchanged forms

Scientific interest in adsorption phenomena of organic vapors has concentrated on synthetic zeolites. Solid–vapor systems containing natural zeolites deserve special attention due to their abundance and environmental applications. Adsorption thermodynamic characteristics for benzene, toluene, n-hexane, and CCl4 were measured on clinoptilolite-rich zeolitic tuffs from Mexico (ZE) and Hungary (ZH) on parent, decationized, dealuminated, and lead-exchanged samples. The clinoptilolite structure released Na+ and Ca2+ by acid treatment and this was accompanied by dealumination to a greater extent on ZE than on ZH. The exchange isotherm of Pb2+ on ZE exhibited a concave type “a” form and accomplished 95% exchange and the tuff was selective at Xi(s)<0.25Xi(s)<0.25. The pattern of adsorption isotherms was the same on all tuffs: benzene > toluene > n-hexane > carbon tetrachloride. The −ΔH¯ values were higher for toluene than for the other adsorbates. Curves of qisostqisost vs coverage decreased with the increment of the adsorbed amount in practically all studied systems. The contributions to the solid–vapor interaction potential were examined using inverse gas chromatography. The specific interaction energy GspGsp was primarily due to adsorbate–framework and adsorbate–cation interactions at low adsorbate pressures producing low surface coverage.

Graphical abstractBy using inverse gas chromatography, adsorption thermodynamic characteristics for the nonpolar organic adsorbates: benzene, toluene, n-hexane, and CCl4 were measured on clinoptilolite-rich zeolitic tuffs. The contributions to the solid–vapor interaction were examined on parent (Z), decationized-dealuminated (Z-Al), and lead-exchanged (Z + Pb) samples. Curves qisostqisost vs coverage decreased with the increment of the adsorbed amount. The specific interaction energy was primarily due to adsorbate–framework and adsorbate–cation interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide