Effect of high voltage pulse treatment on the surface chemistry and floatability of chalcopyrite and pyrite

Abstract The effect of high voltage pulse (HVP) treatment on the surface chemistry and flotation behaviour of chalcopyrite and pyrite were investigated using single mineral. The results indicated that the effect of HVP treatment on pyrite was more significant than chalcopyrite, both in terms of size reduction degree and flotation behaviour. Despite the stronger resistance to mechanical breakage than chalcopyrite, the proportion of −0.053 mm product of pyrite was higher than chalcopyrite for 12.2 per cent in average after HVP treatment of different pulse numbers. The flotation recovery of chalcopyrite was only slightly reduced after HVP treatment of 130 pulse discharges. However, under the same test conditions, the flotation recovery of pyrite was reduced by 64.1 per cent in average. The flotation behaviour of the two single minerals were in agreement with their surface oxidation behaviour in HVP treatment. XPS analysis and EDTA extraction suggested that chalcopyrite surface had only partially oxidized by HVP treatment; whereas pyrite was deeply oxidized with a large amount of S element converted to be sulphate radicals. The relative permittivity of pyrite, chalcopyrite and water was 33.5, 78.1 and 80 respectively, which led to a ratio of electrical field strength inside pyrite, chalcopyrite and water theoretically being 2.39:1.02:1. As a result, pyrite particles had stronger capability to attract electrical breakdown channel than chalcopyrite, and subjected to more severe size reduction and surface oxidation under the same conditions. On the other hand, the slight surface oxidation of chalcopyrite particles was hypothesized to be caused by the active species ( OH, H2O2, etc.) formed during pulse discharge.