Elimination of Sodium Hexametaphosphate Depression on Fluorite Flotation by Lead Ions

Fluorite is a vital strategic nonmetallic mineral resource. In the processing of complex associated fluorite ores, it is typically recovered from flotation tailings. However, its flotation performance is severely depressed by residual sodium hexametaphosphate (SHMP) from upstream flotation operations. In this study, Pb²⁺ was adopted as a high-efficiency activator to reverse the depression of SHMP on fluorite flotation, with octyl hydroxamic acid (OHA) as the collector. Microflotation results showed that Pb²⁺ significantly restored the floatability of SHMP-depressed fluorite, increasing its recovery from only 1.11% to 90.63%. Mechanism studies confirmed a synergistic activation pathway: "liquid-phase consumption and solid-phase reconstruction". In the liquid phase, Pb²⁺ reacted with free SHMP to form Pb-SHMP coprecipitates, thus reducing the depressant concentration in the pulp. On the solid surface, adsorbed Pb-SHMP precipitates and hydrolyzed lead species acted as new active sites for OHA anions.