Influence of x-ray diffraction sample preparation on quantitative mineralogy: implications for chromate waste treatment.

摘要: Powders of chromite ore processing residue (COPR) were mineralogically evaluated using quantitative X-ray powder diffraction (XRPD) to illustrate the impacts sample preparation procedures. Chromite is strongly alkaline, reactive, contains minerals varying hardness and absorption coefficients, exhibits significant amorphicity. This poses a challenge produce powders for XRPD analysis that are sufficiently fine uniform particle size while avoiding mineral reactions overgrinding effects. Dry, hand pulverization different grain sizes, wet, mechanical (micromilling) four milling liquids (cyclohexane, isopropanol, ethanol, water), variable durations (up 15 min) evaluated. Micromilling with light, nonpolar, highly evaporative liquid such as cyclohexane time 5 min mitigated systematic errors microabsorption preferred orientation it produced finer more distributions than hand-pulverized powders, simultaneously affording least preparation. Conversely, use water resulted in extensive hydration during preparation, causing mischaracterization underestimation its reactive brownmillerite content, which can complicate remediation design process COPR. Hand emerged necessary complement quantify Cr(VI)-containing, softer destroyed milling, quantification has also important implications COPR treatment design. The findings this study may be applicable variety geochemically complicated environmental media (metal-contaminated soils, stabilized/solidified media, inorganic waste), points importance method obtain reliable results.