The surface characteristics of natural heulandites/clinoptilolites with different extra-framework cations

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Özet

Natural tuff samples from Miocene aged rhyolitic-pyroclastic rocks containing over 80 % heulandite/clinoptilolite in Western Anatolia (Türkiye) were investigated for their surface characteristics determined by nitrogen adsorption (surface area, pore volume, and pore diameter). Additionally, these surface characteristics were correlated with the cationic compositions of the heulandite/clinoptilolite group minerals. According to the adsorption results after degassing at 150 oC, the study of eleven samples revealed two main pore diameters that were not related to surface area and pore volume, but were partially related to the types and occupancy of extra-framework cations. One set of samples has a pore diameter of about 24 Å, and their total cation content (Na+K+Ca+Mg) ranges from 3.46 to 4.40, and the (Na+K)/(Ca+Mg) ratio ranges from 0.34 to 0.92. The total cation content and (Na+K)/(Ca+Mg) ratio of the other samples with a pore diameter of about 37 Å are between 4.30-5.08 and 1.48-2.85, respectively. After degassing at 300 °C, however, there is a slight difference in the pore diameters of these two sets of samples (about 37 Å and 38 Å). The pore sizes of the samples with a (Na+K)/(Ca+Mg) ratio <1 (heulandite composition) increased from 24 Å to 36-38 Å with increasing degassing temperature, whereas the pore sizes of the samples with a (Na+K)/(Ca+Mg) ratio >1 (clinoptilolite composition) increased from 37 Å to only 38-39 Å. On the other hand, there is no correlation between Si/Al ratios and cation exchange capacities of the samples and their surface characteristics obtained by degassing at two different temperatures.

Orijinal dilİngilizce
DergiClay Minerals
DOI'lar
Yayın durumuKabul Edilmiş/Basında - 2023

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