Rare Earth Elements (REE) are 17 elements including 15 lanthanides (La to Lu), scandium and yttrium. They share many of their properties, both chemical and physical and they naturally occur together in various types of mineral deposits. Rare earth elements are relatively abundant in the Earth’s crust, however they are usually not concentrated in economically exploitable ores. World resources are primarily coming from minerals bastnäsite and monazite. Bastnäsite ( China and USA) provides the largest percentage of the world’s production. Monazite deposits (Australia, South America, China, India, Malaysia, South Africa, and others) are the second largest. Other important REE-bearing minerals include apatite, cheralite, eudialyte, loparite, phosphorites, REE-bearing clays, spent uranium solutions, and xenotime. In addition to the primary sources and leaving aside recycling of REE from end-of-life products as other source, tailings and other by-products from previous mining activities may also hold significant amounts of REE.
While the primary deposits of REE minerals as mentioned above are handled by other research efforts (e.g. FP7 EURARE project), the ENVIREE project (ERAMIN program, second joint call, 2015-2017) assists in placing EU among those possessing techniques for a sustainable and resource efficient recovery of REE from sources normally not used in this context. In the ENVIREE project, a complete extraction process proposal for these secondary sources of REE is targeted. Innovative mineral processing routes, leaching followed by selective and effective separation of the metals are proposed.
In this project, BRGM is in charge of activities dealing with REE bearing minerals beneficiation from legacy or currently produced tailings.
For mineral processing purposes, 2 samples of one ton each were delivered at BRGM. After an exhaustive investigation to select best beneficiation techniques for the reprocessing of each tailing, two pilots were design and operated. These pilots included one or two size reduction stages, froth flotation unit operation (see https://www.youtube.com/watch?v=bzF8w98NxTQ) , gravity separation (shaking tables and multi-gravity separator) and magnetic separation ( Wet High Intensity Magnetic Separator) followed by solid/liquid unit operations (thickener and belt filter).
BRGM also performed a full mass balance reconciliation to characterize the performance of each pilot. Mass balances were then used to carry out a Life Cycle Impact Assessment of designed processes was then performed based on calculated mass balances.
Both pilots were operated in a week and the concentrates were then delivered to other project partners for further dissolution of REE-bearing minerals and selective recovery of REE.
More information about ENVIREE here: www.enviree.eu