One stone, three birds: Recovery of high-quality niobium and iron products from niobium-bearing tailings using low-temperature fluidized hydrogen reduction technology

Abstract

Over 98 % of global niobium production is controlled by just two countries, leading to potential supply risks. The Bayan Obo tailings contain significant amounts of strategic minerals, including iron and niobium. However, the current processes struggle to efficiently recover niobium from these resources. This study innovatively proposes a low-temperature fluidized hydrogen reduction process to treat niobium-bearing tailings from Bayan Obo. Under the optimal parameters of reduction temperature of 475 °C, reduction time of 30 min, and H₂ concentration of 20 %, the reduction product was subjected to magnetic separation. This yielded iron concentrates with 68.27 wt% TFe and a recovery of 96.58 wt%, and niobium products with 17.55 wt% Nb₂O₅ and a recovery of 90.51 wt%. The niobium enrichment ratio reached 5.48. The primary alteration observed in the niobium-bearing tailings during the reduction process is the reduction of hematite to magnetite, exhibiting no phase transformation of the niobium-bearing minerals. During this process, the product exhibited enhanced magnetism, an elevated Fe^2 + content, and the formation of new pores. When the reduction temperature was excessive or the reduction time was unduly prolonged, magnetite was over-reduction to wüstite, resulting in a decrease of magnetism and porosity, which adversely affected on subsequent magnetic separation. At 600 °C, the formation of Fe₂TiO₅ was also observed. This process not only employs hydrogen as a replacement for carbon as a reducing agent to produce high-quality niobium and iron products, but also provides a novel approach for processing analogous iron-bearing tailings, polymetallic ores, and solid waste resources.