Effect of grinding atmosphere on the leaching of mechanically activated pyrite and sphalerite

Abstract

The effects of grinding atmosphere, such as highly pure nitrogen (99.999 vol.%) (abbreviated as nitrogen), less air, and air on the leaching of pyrite and sphalerite mechanically activated for 20 and 120 min, respectively, were investigated. The results indicate that the leaching recovery of mechanically activated pyrite varies with the grinding atmosphere, and increases in the sequence of nitrogen, air, and less air. In contrast, the leaching recovery of mechanically activated sphalerite is insensitive to the different grinding atmospheres. The structural changes of the sulfide minerals mechanically activated under different grinding atmospheres were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD) and X-ray diffraction laser particle size analysis. The results show that the XRD spectra and the specific granulometric surface area ( S G) do not vary with the grinding atmosphere, neither do the S2p and Zn2p XPS spectra of mechanically activated sphalerite and Fe2p XPS spectra of mechanically activated pyrite. However, a change was observed in the S2p XPS spectra of pyrite mechanically activated under different grinding atmospheres. The lattice distortion, S G and the elemental sulfur contents of pyrite and sphalerite mechanically activated under nitrogen were also investigated using XRD, X-ray diffraction laser particle size analysis and a gravimetric method, respectively. The results indicate that the elemental sulfur content of mechanically activated pyrite rises significantly and the lattice distortion ratio ( ε) rises only slightly with increasing grinding time. In contrast, the elemental sulfur content of mechanically activated sphalerite remains constant at 0.5 mg/g while the lattice distortion ratio ( ε) increases rapidly with increasing grinding time. Therefore, the formation of lattice defects on the surface of mechanically activated pyrite, and the lattice distortion on the surface of mechanically activated sphalerite may be mainly responsible for the enhancement of the leaching process for the corresponding sulfide minerals.