Selective leaching of cobalt and iron from cobalt white alloy in sulfuric acid solution with catalyst

• Selective leaching of cobalt and iron form cobalt white alloy is proposed.
• Adding a small amount of HF as catalyst can significantly improve filtration rate.
• Silicon in the alloy is transformed into SiO2 in the residue.
• Most of copper remain in the residue as the phases of Cu and Cu2O after leaching.

In order to improve the leaching ratios and filtration rate during the dissolution of cobalt white alloy, selective leaching of cobalt and iron from cobalt white alloy under controlling potential in sulfuric solution with catalyst is studied. The effects of factors on the variation of leaching ratios, and potential and residue phase change are studied in detail. The results show that appropriate H2SO4 concentration was helpful to improve the separation efficiencies of the metals. The leaching ratios and solution potential increased with the increase of oxidant dosage. When hydrofluoric acid was added as catalyst, the filtration rate would be accelerated with increasing its concentration. Temperature had played an important role in the oxidation capacity of hydrogen peroxide. At the optimal conditions, the leaching ratios of iron, cobalt and copper could reach to 95.00%, 95.00% and 13.50% respectively. Meanwhile, the solution potential was 280 mV and the filtration rate was 9.45 m/h. The results of XRD revealed that the peak intensity of Fe/Co–Si weakened gradually and that of Cu strengthened due to the replacement reaction. In addition, the new phases of SiO2 and Cu2O appeared.