Modal Analysis of Montmorillonite in Bentonites Using Phase Mixing Equation

Abstract

Based on the mass balance principle, mineral contents of the bentonites from Yangxian of Shaanxi province, Queshan of Henan province, and Chifeng of the Inner Mongolia Autonomous Region were estimated by resolving the Phase Mixing Equation constructed from the data of X-ray diffraction, microprobe analysis of montmorillonite grains, and chemical anaysis of the bentonites. The crystal formulas of montmorillonite in the bentonites were calculated based on the anion hydrogen equivalent method. The cell lattice constants of the principal minerals in the bentonites were calculated with a FORTRAN90 program CELLSR. When compared with both methods of the methylene blue absorption and XRD Rietveld quantitative phase analysis, the Phase Mixing Equation was confirmed to be the most effective modal analysis method for determing content of montmorillonite in bentonites with several minerals coexisted.

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“…According to the types of exchangeable cations, bentonite can be divided into four categories: sodium-based, calcium-based, Mg-based, and Al (hydrogen)-based bentonite. 6 The general structure of montmorillonite is Ⅳ (Si 4 ) Ⅵ (Al 2- y -Mg y )O 10 - (OH) 2 , y M + n H 2 O (M + is interlayer exchangeable cation). 7 Its main components are Si, Al, Fe, and Mg oxides.…”