Recovery of boron from high-boron iron concentrate using reduction roasting and magnetic separation

Abstract

The comprehensive utilization of abundant high-boron iron concentrate is of particular significance to China, and the high-boron iron concentrate has not yet been utilized as a source for boron at an industrial scale due to its complex mineralogy and fine mineral dissemination. An innovative method was proposed for recovery of boron and iron from high-boron iron concentrate by reduction roasting and magnetic separation. The effects of reduction temperature and roasting time were investigated and their optimum conditions were determined. The mineralogical changes during roasting were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the pyrrhotite (FeS) contained in the high-boron iron concentrate and the new-formed FeS-Fe solid solution softened or melted at high temperatures owing to their low melting points, and then decreased the metallic iron ratio and accelerated the growth of metallic iron particles. Meanwhile, the magnetite and szaibelyite were converted into metallic iron and suanite, respectively. Consequently, boron was readily enriched into the non-magnetic product and the metallic iron was aggregated to the magnetic concentrate by magnetic separation. Boron recovery of 88. 6% with corresponding B2 O3 content of 14. 5% and iron recovery of 95. 1% with an iron grade of 92. 7% were achieved when high-boron iron concentrate was reduced at 1125 °C for 150 min. Besides, the boron reactivity of the boron-rich non-magnetic product was up to 80. 8%.