Flotation of calcite from apatite of a uranium-carbonate phosphate ore using carbon dioxide

Abstract

The most common method to concentrate apatite from carbonate phosphate ore is reverse configuration using fatty acids as collectors and inorganic acids as apatite depressants, such as H2SO4 and H3PO4. This work evaluates the process based on the separation between apatite and calcite by flotation, in bench and pilot scale, using carbon dioxide injected through the bubble generation system with the use of saponified coconut fatty acid as a collector, as an alternative to the inorganic acids as apatite depressants in the process circuit developed to treat a uranium-carbonate phosphate ore (Santa Quitéria, Brazil). Moreover, the discharge of natural slimes only was evaluated, without the removal of the grinding slimes, which is not observed in apatite flotation plants for weathered material, where the removal of both kinds of slimes is necessary. The circuit proposed in this study provided significant gains in P2O5 recovery. In calcite flotation studies using carbon dioxide, in RG/CL/RCL mechanical cell circuit configuration, considering the overall performance obtained (grinding product + natural fines), the overall P2O5 recovery was approximately 91% and the P2O5, SiO2 and Al2O3 grades were 29%, 11% and 13%, respectively. The results obtained in this study indicated that the process circuit proposed by discharging only natural slimes increases the global P2O5 recovery, and the flotation process based on the injection of carbon dioxide is a potential alternative to concentrate apatite from the Santa Quitéria ore. Furthermore, previous studies have indicated that the use of carbon dioxide instead of inorganic acids as apatite depressants causes less ion accumulation in the process water, which is a major issue mainly in areas with scarce water supply such as the Santa Quitéria region.