Sulfur-bearing minerals in heavy sands from the Grande Côte Operation (site) in Senegal: identification and processing options to reduce sulfur concentrations

Grande Côte Operations (GCO), a Senegalese subsidiary of the Eramet Group, specializes in the recovery of ilmenite, rutile, and zircon. The mine and its two processing plants have been in service since 2014. GCO is a major producer of titanium minerals, which are critical raw materials essential to a wide range of industrial ecosystems. Titanium is used in a variety of applications, including aerospace, defense, medical implants, and consumer products. In this study, we focus on the occurrence of relatively sulfur-bearing samples. high “Sulfur is a deleterious element that affects negatively the application in the welding rod industry) The sulfur concentration in one sample was up to 2%, which is much higher than the usual concentration of 0.05%. Automated mineralogy was used to assess the S-bearing mineral concentration, liberation, and texture to test processing means to extract or reduce the sulfur content. The sulfur is concentrated in framboidal pyrite, an iron sulfur mineral. The pyrite is well liberated indicating a potential to physically recover Sulfur. Processing could be done by density or by a combination of roasting and magnetic separation. It is the latter that is discussed here. The pyrite transforms into hematite at 600°C, roasting for an hour resulted in the transformation of all pyrite into hematite, a magnetic iron oxide. S was eliminated during roasting. The micromorphology of pyrite is pseudomorphically replaced by porous hematite displaying circular textures. Microcracks in the hematite particles are abundant and are interpreted as desulfurization channels of the original pyrite. Some of the pores in hematite mimic the original cubic shape of pyrite. The porous texture of hematite particles might lower the ideal density of these hematite particles. Hematite particles could be successfully removed from the samples by magnetic separation. Based on our findings, we suggest heating pyrite at 600°C for an hour and additional magnetic separation as a viable option for eliminating pyrite from the sample. However, further testing and optimization may be required to determine the feasibility of this process at a larger scale. Pyrite could also potentially be removed (together with zircon) at the density fraction >4.5 g/cm3 by dry density or air table separation. Our study demonstrates the power of automated mineralogy in identifying and quantifying deleterious elements and minerals in complex samples originating from mining operations. By adding textural information, potential process options to remove these minerals and elements can be suggested.