Rare earth elements (REEs) are the backbone of clean energy technologies. However, REEs are mainly available through mining operations outside the U.S, which makes the future supply of these critical materials at risk. To ensure the U.S. energy security, it is now vital to develop domestic sources of REEs. Global phosphate deposits contain 27 million tons of REEs, equal to approximately 200 years of current world demand. Near 38% of these REEs end up in phosphogypsum (PG) waste during phosphate fertilizer production. PG stacks in central Florida occupy acres of potential farm land and pose adverse environmental effects to their surroundings. Recovering REEs from PG is the first step towards a trash-to-treasure transformation. Here we studied REEs location and stability in RE-doped CaSO4/Ca3(PO4)2 systems using solid state calorimetry. We also developed mixed solvent electrolyte simulations to predict and designed experiments to verify the solubility of NdPO4 (as a model compound) under various acidic conditions. This study provides insight into developing an efficient recovery process which could generate 25,000 tons of REEs annually from PG waste.

Rare earth recovery from phosphate fertilizer production waste

253rd National Meeting (2017)

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