Extraction of niobium from low-grade niobium tailings by molten oxide electrolysis

Numerous undeveloped and underutilized niobium deposits are located inside Bayan Obo's tailings. Niobium is challenging to extract from low-grade niobium slag using traditional methods. In this work, molten oxide electrolysis was used to prepare metallic niobium and niobium-iron alloys. Our findings reveal that the reduction of Nb(V) on a tungsten electrode operates through a two-step, five-electron transfer process: Nb(V) → Nb(II) and Nb(II) → Nb(0). Meanwhile, on an solid iron electrode, the reduction follows a three-step process: Nb(V) → Nb(IV), Nb(IV) → Nb(II) and Nb(II) → Nb(0). In the co-deposition approach, Fe(III) is first deposited on the tungsten electrode to form a Fe film through the reaction Fe(III) + 3e → Fe(0). Subsequently, Nb(V) is reduced on this iron film, yielding NbFe intermetallic compounds. Additionally, we examined the transport and diffusion rates of Nb ions as they transition to Nb(0) on inert tungsten, solid iron, and during co-deposition. The results highlight that the co-deposition method yields FeNb and Fe 2 Nb alloys that are easier to separate and demonstrate superior diffusivity, with D Nb(II) measured at 1.80×10 -5 cm 2 s -1 during the reduction process. This research highlights a promising pathway toward enhancing niobium production and utilization in high-demand industries.