Depression behavior and mechanism of sodium silicate on bastnaesite and parisite flotation

Parisite (CaCe2(CO3)3F2) and bastnaesite (CeCO3F), important rare earth minerals, have different elemental compositions and crystal structures. Their flotation behavioral differences under commonly used sodium silicate (SS) depressant and hydroxamate collector are important for rare earth ore beneficiation, which is still unknown. In this study, the effect of sodium silicate on bastnaesite and parisite flotation with octyl hydroxamic acid (OHA) as collector was comparatively investigated through microflotation, zeta potential measurements, X-ray photoelectron spectroscopy (XPS), and mineral crystal computational analysis. The results indicated that the inhibition effect of SS on parisite was significantly stronger than that on bastnaesite. SS had little effect on the adsorption of OHA on bastnaesite surface, rendering a slight inhibition on bastnaesite flotation. However, SS strongly hindered the adsorption of OHA on parisite surface, rendering the heavy inhibition on parisite flotation. The inhibition mechanism of SS on parisite was due to the reaction of the calcium species with silicate, thereby forming Ca-SiO3 hydrophilic complex on parisite surfaces. This hydrophilic complex hindered the adsorption of OHA and increased the hydrophilicity on parisite surface, thus, causing significant inhibition on parisite flotation.