Bubble attachment and Amyl Xanthate adsorption to copper-activated sphalerite

Abstract

Sphalerite (ZnS) is a primary source of zinc metal. It usually coexists with other sulphide minerals such as pyrite (FeS 2 ) and galena (PbS). Its concentration is accomplished by froth flotation using short-chain thiol collectors such as xanthate. Due to its unique chemical and structural characteristics, the concentration of sphalerite by flotation requires Cu-activation, which is a process of making the mineral susceptible to reactions with the thiol collectors. The high amount of copper sulphate consumption is a big challenge for zinc processing plants, and the parameters that lead to a significant amount of copper sulphate usage for sphalerite activation is not wellunderstood. Based on the literature review and zinc processing plants reports, process water quality and the presence of pyrite during sphalerite Cu-activation could be two main factors affecting the activation that are the main focus of this thesis.To develop insight into mechanisms of Cu-activation of sphalerite and pyrite, Cryogenic X-ray Photoelectron Spectroscopic (Cryo-XPS) and zeta potential measurements were applied. The Cryo-XPS results showed that Cu-activation of sphalerite was an ion exchange reaction with CuS-type layer formation, while pyrite Cu-activation was governed by redox reactions with CuFeS 2 -type layer development. Depth profiling after 10 min activation revealed Cu diffusion into the sphalerite lattice up to 10 nm, while the thickness of the activation product on pyrite surface was less than 3 nm. The zeta potential studies confirmed proposed surface products on the minerals by Cryo-XPS.Hydrophobicity and many other surface properties of Cu-activated sphalerite can be changed by dissolved ions available in the process water (e.g. calcium, magnesium and sulphate). The effect of Ca(NO 3 ) 2 , Mg(NO 3 ) 2 , MgSO 4 and CaSO 4 on the surface properties of Cu-activated sphalerite was studied using sessile drop Contact Angle (CA), Cryo-XPS and zeta potential measurements. The CA measurements showed that the hydrophobicity of sphalerite developed after Cu-activation, but the presence of 3×10 -2 M Ca(NO 3 ) 2 or Mg(NO 3 ) 2 or MgSO 4 decreased its hydrophobicity. The XPS data showed that the effect of these ions appeared to be the same, namely a decrease in Cu adsorption and polysulphide formation. Zeta potential measurements confirmed the presence of calcium and magnesium ions on the sphalerite surface.Sphalerite is not the only sulphide mineral whose flotation behaviour can be affected by the presence of Cu ions in solution. The possibility of inadvertent Cu-activation of pyrite and its undesirable flotation is one factor accounting for the effective separation of sphalerite from pyrite.The surface hydrophobicity and components of the Cu-activated sphalerite were measured to investigate Cu adsorption kinetics of sphalerite in the presence of pyrite using a novel experimental approach of High-Speed Video Microscopy (HSVM) and Cryo-XPS. HSVM method allowed for ii in-situ liquid film Drainage rate (DR) and bubble-mineral CA...