A cleaner recovery of rare earth bearing minerals by Pickering emulsification: Improvement of processing conditions toward an economic operation

Abstract

The production of rare earth elements (REE) is crucial in modern world. They are increasingly utilized in numerous applications, especially in clean- and high-tech sectors. The froth flotation is commonly considered for the concentrate production of REE, from their bearing ore, in the course of mine-to-metal production chain. However, various environmental drawbacks are present in conventional flotation processes such as large amounts of tailings, chemical reagents and surfactants all released in the surroundings of the operations. In our previous work, we introduced the Pickering emulsification as a novel approach, and cleaner alternative to the froth flotation, which potentially offers multiple ecologic and economic advantages, where we achieved a recovery of about 50% of REE, and an enrichment ratio of 2.9. Here, we investigated the effects of two essential process parameters such as mixing intensity (i.e., changing the impellers speed), and shear uniformity (i.e., comparing the performance of two hydrodynamically different impellers) to improve the process performance. We achieved an optimum rotational speed and energy consumption with a Maxblend impeller, where the size of the emulsion droplets showed much more uniform distribution. Thus, the recovery and the enrichment ratio rose up to 65% and approximately 3.85, respectively, after one single stage of emulsification. We have shown that such conditions outperform the froth flotation besides the environmental advantages.