Bio-weathering Using Shewanella oneidensis MR-1 Enhances Selective Recovery of Rare Earth Elements from Alaskan Coal Mines

Coal mines in Alaska with high rare earth elements (REEs) levels (286-524 mg/kg) serve as an alternative domestic source for REEs. Existing leaching/separation technologies fail to selectively recover REEs from the feedstock and require downstream multiple purification stages that increase the overall operational cost. This study aims at bio-weathering coal from two Alaskan coal mines (Wishbone Hill and Healy) at three density fractions (1.3 float, and 1.3 and 1.5 sink) using Shewanella oneidensis MR-1 for achieving higher selective REEs recovery in one-step process. Optimizing the bio-weathering process by varying solids percentages (5.7 to14.3% w/v), particle size (-14 to -200 M), incubation temperatures (30 to 34 °C), and inoculum dosing (0.2 to 1% v/v) resulted in highest recovery of Neodymium (75.3%) and total REEs (98.4%) from 1.3 float Wishbone Hill and 1.3 sink Healy coal, respectively. When compared to the chemical leaching process, bio-weathering enhanced selective recovery of REEs including Scandium, Yttrium, Ytterbium, Terbium, Erbium, and Lutetium from Healy coal at low density, and Yttrium from Wishbone Hill coal at high density. The results indicate the future scope for developing cost-effective selective REEs recovery processes that may address the global critical minerals supply chain risk.