Bentonite Powder XRD Quantitative Analysis Using Rietveld Refinement: Revisiting and Updating Bulk Semiquantitative Mineralogical Compositions

Bentonite is a claystone formed by complex mineralogical mixture, composed of montmorillonite, illite, and accessory minerals like quartz, cristobalite, feldspars, carbonates, minor amounts iron oxy-hydroxides. presents complexity at various scales: (1): single mineral may present different chemical composition within the same quarry (e.g., feldspars solid solutions); (2): montmorillonite variability in cation-exchange distribution while illite be presented as mixed-layer with smectite sheets; (3): hardness crystal size are larger than clay minerals, preventing uniform grinding bentonite. The FEBEX bentonite used originally from Almería (Spain), it predominantly calcium, magnesium, sodium This Spanish has been hydrothermally altered laboratory scale for 7–14 years. A thermal gradient was generated heating disk pressed powder, simulating metal waste canister, contact compacted sample. Hydration forced opposite direction. XRD recorded patterns were very similar. In order to minimize bias semi-quantitative determination methods, Rietveld refinement performed using BGMN software structural models. Confidence quantification main phases allows us convincingly detect other subtle changes such presence calcite hydration front, right interface between saturated unsaturated bentonite, or goethite, not hematite, near source hydration. Smectite component 72 ± 3% consistent ~10% comparable previous characterizations.