Ion exchange equilibrium and structural changes in clinoptilolite irradiated with β- and γ-radiation: Monovalent cations

Daniel Moraetis*, George E. Christidis, Vasilios Peridikatsis

*Corresponding author for this work

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Thermodynamic calculations of ion-exchange reactions were applied for clinoptilolite in a natural state and after irradiation with three doses of β-radiation (1012, 1015, 3 × 1016 e/cm2) and γ-radiation (70 Mrad). Samples were equilibrated with binary systems of K+ ↔ Na+ and Cs+ ↔ Na+ at 25° and a total normality of 0.025 N. Selectivity for K was not affected after β-radiation with doses of 1012 and 1015 e/cm2 (ΔG° = -6.37 kJ/equiv, lnKα = 2.58 for the original clinoptilolite), whereas it increased considerably after 70 Mrad of γ-radiation (ΔG° = -7.88 kJ/equiv, lnKα = 3.18). Selectivity for Cs+ increased for the clinoptilolite irradiated with β-radiation (1012, 1015, 3 × 1016 e/cm2) and γ-radiation (70 Mrad). ΔG° and lnKα for original sample and Cs+ ↔ Na+ were -7.33 kJ/equiv and 2.96, respectively. Irradiated samples with β-radiation 1012, 1015, 3 × 1016 e/cm2 and 70 Mrad γ-radiation yielded ΔG° and lnKα -7.41, -8.83, -8.60, -8.25 kJ/equiv and 2.99, 3.57, 3.47, 3.33 for Cs+ ↔ Na+, respectively. Remarkable amorphization of clinoptilolite was observed after exposure at the highest dose of β-radiation (3 × 1016 e/cm2) with a concomitant decrease in cation-exchange capacity (CEC). Crystallographic parameters and especially exchangeable cation site coordinates were refined for all samples with the Rietveld method. Cesium-saturated samples exhibited changes in the cation sites Cs2 and Cs3, which are next to clinoptilolite channel walls with lower Al3+ for Si4+ substitution. The observed changes include a shift in cation sites Cs2 and Cs3 toward channel walls and occupancy decrease in site Cs2.

Original languageEnglish
Pages (from-to)1714-1730
Number of pages17
JournalAmerican Mineralogist
Volume92
Issue number10
DOIs
Publication statusPublished - Oct 2007

Keywords

  • β-radiation
  • γ-radiation
  • Clinoptilolite
  • Ion exchange
  • Rietveld refinement
  • Thermodynamics

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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