The role of mineralogy study in the desulfurization flotation of vanadium-titanium magnetite

• Fine-grained and unevenly embedded pyrrhotite was the dominant S-bearing mineral. • Pyrrhotite was tightly contiguous with ilmenite and magnetite. • 81.59 % of the pyrrhotite was liberated at −0.075 mm grinding particle sizes. • Desulfurization flotation tests were carried out based on the mineralogy study. • Optimized desulfurization conditions resulted in 0.05% residual S in tailings. Vanadium-titanium magnetite is a paragenetic ore primarily composed of iron (Fe), vanadium (V), and titanium (Ti). In typical beneficiation processes, magnetite is first separated from vanadium–titanium magnetite through a combination of magnetic and gravity separation methods. The remaining ilmenite tailings are subsequently subjected to desulfurization and Ti enrichment treatments. In this study, the mineralogical characteristics of vanadium–titanium magnetite were first analyzed for desulfurization flotation. The primary useful metallic minerals in this ore were ilmenite and magnetite, along with minor amounts of sulfur-bearing minerals. Of that, approximately 98 % of the sulfur (S) existed as sulfides, predominantly pyrrhotite. Notably, 81.59 % of pyrrhotite particles achieved a liberation degree exceeding 80 % at a particle size less than 0.075 mm. Combined with the mineral dissociation analysis of pyrrhotite, a grinding particle size test was conducted at a −0.075 mm proportion of about 80 %, determining the optimal grinding particle size to be 85 % of −0.075 mm. Under the optimal desulfurization flotation conditions with a grinding particle size of 85 % less than 0.075 mm, a copper sulfate (CuSO 4 ) dosage of 300 g/t, and a pulp pH of 4, a desulfurization of 91.33 % was achieved, and the S grade in the tailings was only 0.05 %. The difficulty in floating the remaining sulfides was due to their fine embedded size, close associative relationships, and low liberation, as determined by a process mineralogical study of the tailings. A process mineralogy of this vanadium-titanium magnetite, conducted both before and after desulfurization, provides a foundation basis for efficient desulfurization and separation.