Lime-based COPR and soda ash COPR have different leaching behavior and compositions based on previous study. Geochemical modeling showed that Cr(Ⅵ)-Hydrotalcite emerged as a potential bearing phase for Cr(Ⅵ) in both original soda ash COPR and column leached soda ash COPR. However, bulk XRD analyses can only indicate chromite as the crystal phase in soda ash COPR. Micro-XRF, micro-XANES, and micro-XRD analyses could provide a further accurate determination of the distribution and the speciation of Cr(Ⅵ). Preliminary analysis confirms the presence of Cr(CI) hydrotalcite in COPR. This crucial information could provide invaluable information to improve Cr(Ⅵ) treatment design and to optimize release and availability for reduction.
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