Researcher: M.Sc. Santeri Kurkinen, Department of Separation Science, LUT University
Supervisors: Prof. Tuomo Sainio and Dr. Sami Virolainen, LUT University
Description of the project: Rare earth elements (REEs) are a set of 17 elements with extraordinary properties. Their numerous applications include electronics, LEDs, high strength magnets, automotive catalytic converters, and high temperature superconductors. REEs are not particularly rare in Earth’s crust, but they are difficult to extract and purify cost-effectively.
Besides ores, REEs are found in various by-products of minerals processing. Phosphogypsum waste (PG), which is formed in phosphate fertilizer production, may contain 0.2 wt-% of REEs. PG is available in huge quantities. In Finland alone, more than 1.5 million tons of PG is produced and piled annually.
REEs can be leached from PG with, e.g., sulfuric acid. Interestingly, leaching can be done under very mild conditions if functionalized polymeric particles, called ion exchange resins, are added to the leaching reactor. The polymer particles quickly bind the liberated REE ions from the solution, thus increasing the leaching yield.
The PuREE project aims at further developing the “resin-in-leach” process. Significant improvements in leaching efficiency and selectivity are achieved by optimizing the chemistry of the functionalized polymer. Once the REEs are bound to the polymer, they must be recovered to reuse the polymer. The sustainability of this step is improved by using biodegradable chemicals for REE recovery. Further purification of the REEs is done in a separation column using another type of polymeric separation material.
The PuREE project produces new data and process options for sustainable production of REEs from a secondary source in Finland.