Ion exchange resins for the treatment of cyanidation tailings: Part 3 – Resin deterioration under oxidative acid conditions

Oxidative acid eluents comprising of H2O2 and H2SO4 have been proven to be effective in eluting base metal cyanide complexes from strong base resins. This study found that the repeated cycling between alkaline cyanide conditions and oxidative acid conditions does not affect the strong base or the total base capacity of strong base resins. However, it was found that a significant reduction of net operating capacity of the ion exchange resin bed, along with a small reduction of the total base capacity of the resin, takes place when this eluent is repeatedly used to elute resins loaded with a mixture of metal cyanide complexes. The reduction of the total base capacity is thought to be due to the oxidation of the resin by the oxidant in the presence of Cu2+ ions. A precipitate of copper hexacyanoferrate was detected in resin loaded with a mixed copper and iron cyanide solution. While the formation of this precipitate did not appear to have an impact on the total base capacity of the resin, it affected the net operating capacity of resin beds. These two processes gave rise to an approximately 1–3% reduction of the net operating capacity of the ion exchange resin columns per loading/elution cycle.