Sedimentation of Fine Arsenopyrite with PEI and the Flotation Significance

Abstract

The flotation of fine mineral particles is always a difficult problem. The flotation of fine arsenopyrite particles (−20 μm) in a sodium butyl xanthate (SBX) system was studied by using polyethyleneimine (PEI) as a flocculant. The flocculation properties of PEI on fine arsenopyrite were studied using sedimentation tests. The results showed that the optimum pH for the sedimentation of PEI was approximately 7.5; the higher the molecular weight (M.W.) of the flocculant, the better the sedimentation effect. In the flotation experiments, it was found that the flotation recovery of PEI-3 with high M.W. as flocculant was only 57%, while the flotation recovery of PEI-2 with medium M.W. was 90% under respective optimum conditions. The contact angle tests showed that the natural contact angle of arsenopyrite was 37°; the addition of moderate PEI-2 had a slightly negative influence on the hydrophobicity of arsenopyrite in the SBX system. From the size analysis results, the maximum particle size (D100) and median size (D50) of the arsenopyrite increased from 20 and 11 μm to 48 and 28 μm after treatment with 40 mg/L PEI-2, a size more conducive to bubble capture. From the combination of these results, it can be concluded that PEI-2 improved the flotation of fine arsenopyrite mainly by increasing the particle size to a suitable range through flocculation. The XPS results indicated that the adsorption of PEI-2 on the arsenopyrite surface was due to the chemisorption between the imino group and the active Fe/As sites. Applying PEI-2 to a fine disseminated arsenopyrite-type gold ore, a concentrate containing 36 g/t Au with a Au recovery of 88% can be obtained.