Fundamental Studies of the Surface Properties of Millerite under Different Pulp Potentials and Water Chemistry

• Author / Creator

  Zhao, Hua Run

• Millerite (NiS) is one of the less common nickel-bearing minerals that is typically formed as a replacement for pentlandite. Due to the scarcity of millerite, its flotation behavior is not well understood in literature. In this study, the surface properties of millerite were investigated. Cyclic voltammetry coupled with Fourier-transform infrared spectroscopy (FTIR) and contact angle measurements were used to study xanthate adsorption on millerite surface under different pulp potentials and water chemistry. In addition, micro-flotation tests were conducted on single and mixed mineral systems to evaluate the possibility of millerite depression from chalcopyrite by controlling pulp potentials. Studies on electrochemistry and wettability at pH 9 suggest that nickel (II) ethyl xanthate forms initially at a lower potential and is responsible for imparting a slight hydrophobicity to millerite surface. As the potential is increased above the reversible potential for dixanthogen formation, a steep increase in anodic current along with increased hydrophobicity was observed. This indicates that at higher potentials dixanthogen becomes the predominant species formed and is responsible for increased hydrophobicity observed for millerite. At pH 12, the oxidation of millerite surface occurred above Eh = 0.1 V (SHE), which created a hydrophilic layer that prevented the xanthate from adsorbing on the millerite surface. X-ray photoelectron spectroscopy analysis of the oxidized millerite surface identified the presence of nickel hydroxide and nickel sulphate species. Micro-flotation studies showed that millerite recovery decreased with increasing potential under oxidizing conditions at pH 12. Mixed mineral flotation studies showed that millerite and chalcopyrite are both strongly floatable under open circuit potential at pH 12. However, as potential is increased to more oxidizing conditions (above 0.2 V), chalcopyrite remains strongly floatable while millerite becomes depressed. This finding showed that a large oxidizing potential range exists where chalcopyrite can be potentially separated from millerite at pH 12. In conclusion, this study investigated a pathway for millerite separation from chalcopyrite through controlling pulp potentials, which is important for improving copper concentrate quality in the Cu/Ni mining industry.

• Subjects / Keywords

  • Mineral Flotation, Millerite, Electrochemistry

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-2f28-d993

• License

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