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Abstract:
Fluorite-rich sludge is the main waste from dicalcium phosphate (DCP) production. This sludge consists of 40–60% of CaF2, which precipitates during the reaction between fluorapatite (the main component of raw phosphorite material) and HCl. In addition, the sludge contains elevated amounts of critical elements such as REEs. In this study, two industrial sites producing DCP in Spain were studied to assess the potential valorization of these sludges. Currently, almost 2 Mt of waste remains landfilled in these sites. The concentrations of Y, La, Nd, Dy, and Gd found within the residues are about 1100 ppm, 450 ppm, 300 ppm, 80 ppm, and 75 ppm, respectively. Fluorite, being the host mineral of the REEs, occurs as very fine-grained spherules (<5 μm) that are smaller than other minerals in the waste (quartz, gypsum), favoring the options of hydrometallurgical separation. REEs extraction from the fluorite could be an advantageous option, if separated from uranium, which is the main environmental concern of the future valorization of this kind of waste.
