Recovery of rare earth elements from fluorite sludges from dicalcium phosphate industry

The management and final disposal of waste containing radioactive elements is currently challenging in many countries due to the large volumes and their potential radiological risk. A promising alternative is the re-use to reduce the amount of waste to be disposed and to provide additional profit to the companies that generates this residue. This can be the case of fluorite sludge produced after the manufacturing of dicalcium phosphate. In this study, the initial stage of waste characterisation of fluorite sludge from two industrial sites, one active in Flix (NE Spain) and another one consisting of legacy ponds and stockpiles at El Hondón, in SE Spain, is reported. Fluorite sludge consists of 40-60% of CaF₂, which precipitates during the reaction between fluorapatite (main component of phosphorite raw material) and HCl. This fluorite is very fine grained, with most particle sizes below 5 microns, and contains significant amounts of REEs, mainly Y, La, Ce and Nd, (0.2wt%, 800 ppm, 600 ppm and 300 respectively), especially in the sludge that precipitated in the reaction tanks. Concentration of the other REEs vary from 18 ppm to 167 ppm. Prices for the top grade REEs are high at the moment, and with time, as the reserves become scarcer, the prices will grow even more. Also, fluorite concentrate can be a valuable commodity. Taking into account the large amounts of disposed waste in both sites, and the concentrations of REEs, their recovery can be a great opportunity to reduce the amount of waste to be managed, and to provide new sources for these critical raw materials. So, current investigations are focused on cost-effective methodologies of fluorite separation and concentration and REEs extraction.