A clean separation process using pretreatment-flotation for refractory mixed concentrates

Abstract

• A new pretreatment-flotation separation method for galena and chalcopyrite was developed. • The modification mechanism of S 2- conversion to SO 4 2- on galena surface was revealed. • Separation test results of Cu-Pb sulfide mixed concentrate validates the theoretical analysis. In this paper, a clean separation technique of galena and chalcopyrite that innovatively combined a sulfuric acid pretreatment with collector-free flotation was proposed. X-ray diffraction (XRD) analysis, Scanning Electron Microscopy (SEM) determination, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) measurement, and flotation experiments were carried out to research on the surface differentiation of galena and chalcopyrite with sulfuric acid and the effect on their flotation performance. XRD analysis showed that significant characteristic peaks of a new species of lead sulfate (PbSO 4 ) were formed in galena after sulfuric acid pretreatment, while chalcopyrite was not affected at all. SEM analysis and floatability results confirmed the effect of sulfuric acid on selective oxidation of galena surface. ToF-SIMS results further provided strong evidence for the conversion of sulfur ions to sulfate ions on galena surface. Lead sulfate species formed on the pretreated galena were detected at a thickness of 0–80 nm, which led to its loss of hydrophilicity and floatability. The experimental results of pretreatment-flotation separation of galena-chalcopyrite mixture and copper-lead sulfide mixed concentrate were in good agreement with the theoretical analysis. The results showed that the new method could effectively and thoroughly separate lead sulfide from copper sulfide ore, and the sulfuric acid in this technology could be recycled in the periodic pretreatment process. This work can enrich the surface inhibition theory of galena by sulfuric acid and provide an effective way for the separation of lead-copper sulfide ore.