Activation flotation and activating mechanism of cyanide-depressed pyrite using sodium persulfate and ferrous sulfate

Abstract

Cyanide tailings were produced by cyanidation gold extraction and normally contained a large amount of unrecovered valuable metals. At present, there are few pieces of research on the activation flotation recovery of useful minerals in cyanidation tailings. In this paper, the activation flotation of cyanide-depressed pyrite using sodium persulfate (PDS) and ferrous sulfate (Fe(II)) was systematically studied by microflotation tests. The activating mechanism was analyzed by FTIR spectroscopy, zeta potential measurement and electron paramagnetic resonance (EPR) analysis. The microflotation tests showed that pyrite flotation was deeply depressed in the presence of sodium cyanide (NaCN). The flotation of cyanide-depressed pyrite could be largely improved by the addition of individual PDS or combined PDS and Fe(II). The dosage of combined PDS and Fe(II) was lower and their activating effect was better than using PDS alone. Zeta potential measurements and FTIR analysis revealed that NaCN was adsorbed on the pyrite surface to generate the hydrophilic ferricyanide, which can reduce the pyrite floatability. The individual PDS or combined PDS and Fe(II) could react with ferricyanide to destroy the hydrophilic adsorption layer and restore the hydrophobicity of pyrite surface. EPR analysis indicated that the oxidation system of pyrite with combined PDS and Fe(II) could produce more powerful SO₄⁻• and HO• than individual PDS. The radical scavenging experiments further confirmed that the generating free radicals were the active species for the destruction of ferricyanide and reduction of the activator dosage.