Galvanox takes advantage of the galvanic effect between chalcopyrite and pyrite.

• Chalcopyrite is a semiconductor, and therefore corrodes electrochemically in oxidizing solutions.
• In ferric sulphate media, the overall leaching reaction is as follows:
  CuFeS₂(s) + 2 Fe₂(SO₄)₃(a) → CuSO₄(a) + 5 FeSO₄(a) + 2 S⁰(s)

• This reaction may be represented as a combination of anodic and cathodic half-cell reactions:
  Anode: CuFeS₂ → Cu²⁺ + Fe²⁺ + 2S⁰ + 4e^-
  Cathode: 4 Fe³⁺ + 4 e^- → 4 Fe²⁺

Unassisted Chalcopyrite Leaching

Galvanox Chemistry

• Typically, chalcopyrite surfaces are passivated (i.e., they become resistant to electrochemical breakdown) in ferric sulfate solutions at even modest solution potential levels.
• It is widely held that this results from the formation of some sort of passivating film on the mineral surface that most likely consists of an altered, partially Fe-depleted sulfide layer.
• Because of this, most investigators have assumed that it is the anodic half-cell reaction that limits the overall rate of leaching.
• However, we discovered that it is primarily the cathodic half-cell reaction (i.e., ferric reduction) that is slow on the chalcopyrite surface.

Galvanically-assisted Chalcopyrite Leaching