Effective recovery of niobium from complex resources by reduction-sulphuration process

• Reconstruction of complex multiple niobium minerals into sulfide. • Recovering lithophile niobium by reduction-sulphuration process from slag. • Efficient separation of niobium and titanium. • Revealing the transformation mechanism of niobium minerals into sulfide. The rising demand for critical niobium resources exacerbates reliance on complex resources due to limited high-grade ore reserves. However, efficient and selective separation of niobium from complex resources such as symbiotic minerals and tailings remains a significant challenge. Here, a high temperature reduction-sulphuration strategy was proposed for transforming and separating niobium from complex symbiotic Bayan Obo ore resources. By introducing a sulfurizing agent (pyrite) and a reducing agent (coke) at high temperatures, niobium-bearing minerals were converted into iron niobium sulfide (FeNb 2 S 4 ), which was separated from slag naturally. The reduction-sulphuration mechanism of niobium-bearing minerals includes reduction, migration, and sulphuration processes. When adjusting the additive amount of sulphuration agent, the maximum recovery rate of niobium was 89.25%. The high temperature reduction-sulphuration strategy alters the distribution of niobium in complex mineral resources, enabling highly efficient and selective separation of niobium. This strategy provides an effective solution for the world's abundant and complex low-grade niobium-bearing resources.