Behaviour of dissolved arsenic in the electrolyte purification process in copper electrorefming

摘要

An electrochemical research method for the determination of the cathodic behaviour of As(Ⅲ) and As(Ⅴ) in electrolyte purification bleeds is introduced. The method includes polarisations measurements with cathodic polarisation curves and short-term potentiostatic electrolysis experiments. According to the polarisation measurements, the electrochemical behaviour of trivalent and pentavalent arsenic is completely different. The polarisation curves determined for As(Ⅲ) show three clear plateaus as the cathodic overpotential increases. In contrast, the polarisation measurements carried out with As(Ⅴ) do not reveal as clear inflection points. After the copper deposition plateau, the polarisation curves show only a hump indicating the formation of arsenides. Gas evolution begins at a lower overpotential, of 70 mV, than for As(Ⅲ) and the gas formed is also rich in arsine AsHs. The results show clearly that the formation of copper arsenides is hindered by As(Ⅴ), whereas the formation of arsine is depolarised.