NioCorp said it achieved a rare earth dissolution rate of 86%–95% from Elk Creek project ore through hydrochloric acid leaching and a loading rate of up to 99% rare earths in a follow-on solvent extraction recovery step.

NioCorp announced in early February that its demonstration-scale processing plant at L3 Process Development in Quebec, Canada successfully produced a high-purity mixed rare earth concentrate. These results, according to Colorado, USA-based NioCorp, support the technical feasibility of separating high-purity oxides of several key magnetic rare earths from ore at the company’s Elk Creek critical minerals project in southeast Nebraska.

NioCorp said its patent-pending demonstration scale rare earth extraction and purification solvent extraction process operation is ongoing in Trois-Rivieres, Quebec, using solutions generated by the upstream operations of the demonstration plant. The rare earths were then precipitated out of solution, producing a solid containing 6% praseodymium oxide, 25% neodymium oxide, 0.35% terbium oxide and 1.6% dysprosium oxide, with the balance of the solids consisting primarily of rare earths with minor base metal impurities.

Based on these results, and subject to additional demonstration testing, L3’s process engineering team determined that overall recoveries for these four magnetic rare earths are likely to be greater than 92% and meet commercial purity specifications for magnetic rare earth oxides. 

These results, said NioCorp, are in line with bench- and pilot-scale testing of L3’s rare earth recovery system, as well as hydrometallurgical performance models that have been run on the rare earth recovery process upon which the demonstration plant is based. And, the company continued, they are in line with previous published results at demonstration-scale in producing high-purity scandium oxide at an overall recovery rate of approximately 92%. Scandium behaves very similarly to rare earths in solution while it is being separated and recovered into a high-purity oxide product.

L3 is currently completing the assembly and commissioning of additional solvent extraction steps that will be run in concert with the rest of the demonstration plant to confirm these recovery numbers.

NioCorp noted that an economic analysis has not been completed on the rare earth mineral resource comprising a portion of the Elk Creek project – where the primary product will be ferroniobium – and further studies are required before determining whether extraction of rare earth elements can be reasonably justified and economically viable after taking into account all relevant factors.