Effect of oxygen on the CuCu 2SeAg system

Abstract

A large percentage of the world's silver supply is produced as a byproduct of the copper industry. The silver is found in the copper anodes which are upgraded by electrorefining. The anode composition and the phase distribution in the anode affect the electrorefining step and subsequently the separation processes for the various elements which are present in the anode. In particular, the distribution of silver and the other precious metals between the copper-rich phase and the copper selenide rich phase in the anodes has an effect on their recovery. In the present research the effect of oxygen on the CuSeAg (Pt, Pd, Au, or Ni) system was studied. Samples of copper-rich liquid and copper selenide-rich liquid were equilibrated at temperatures in the range of 1130°C to 1223°C. The silver content of both the phases reached a constant value after about two hours. Also, the oxygen content of the copper-rich phase reached an essentially constant value. However, the oxygen content of the copper selenide rich phase continuously increased due to the production of oxide phases in the melt. The oxygen content of both phases increased with the partial pressure of oxygen. At high oxygen potentials the silver distribution ratio between the copper and the copper selenide phases decreased because of the oxidation of some of the copper selenide to copper oxide. Silver as either oxide or metal has a much higher solubility in copper oxide than copper selenide and thus the silver distribution ratio decreased. Nickel additions resulted in a significant increase in the oxygen content of both phases.