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A Cu-Co ore from Katinga Province, the Republic of Congo containing 1.5% Co and 1.6% Cu was tested to determine the leachability of Cu and Co using sulphuric acid and hydrogen peroxide mixtures at different conditions. Without hydrogen peroxide, the maximum extraction of copper and cobalt were found to be ~80% and ~15%, respectively when the acid concentration was varied between 0.36 - 1.1M. When hydrogen peroxide was added (0.008-0.042M), Cu recovery was enhanced to ~90%. Recoveries of ~90% of Co could be achieved at 20ºC, using leachants consisting of 0.36M sulphuric acid and 0.025M hydrogen peroxide after 3 hours. The reaction time to reach 90% Co extraction was reduced to less than 2 hours at 30ºC. Stabcal modelling of the Eh-pH diagrams shows the importance of hydrogen peroxide as a reductant. The decrease of solution potential (300-350 mV) by adding hydrogen peroxide was confirmed by Eh measurements during the tests. The leaching follows the shrinking core model kinetics, where the rate constant is linearly dependent on hydrogen peroxide concentration in the range 0-0.025M and proportional to (1/r2) where r is the average radius of the mineral particles. The activation energy for the leaching process is 72.3 kJ/mol

The leaching of Mo, Cu and Fe from MoO 3 calcines (59-61% Mo) containing 1-2% Cu, 1-2% Fe and other impurities produced from roasting molybdenite (MoS 2 ) concentrate was examined using water and a series of chloride lixiviants, including NH 4 Cl (0. Although not required, Fe was removed to <0.6% whereas most other metal impurities were removed to <0.1%. Pilot plant trials over 7 campaigns, each treating 2.0-2.2 tonnes of MoO 3 calcine containing 2.1% Cu using 1.44M NH 4 Cl and 0.97M HCl at an ambient temperature yielded final products containing 0.22% Cu as required. Mass balance calculations (closure to 96-99%) of the pilot plant trials confirm that the Mo loss during leaching is around 0.5%. Research Highlight We determine the process chemistry of leaching Cu from MoO3 calcine to reduce its content to <0.5% A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2  The optimum leaching conditions to treat calcines containing 1% Cu (0.6M NH4Cl, 0.7M HCl at ambient temperature) were adopted to remove impurities to <0.5% Cu, <0.6% Fe and <0.1% for other impurities  The dissolution of Mo by acid was minimized by the precipitation of ammonimum molybdate  Stabcal was used to model the speciation of the dissolution process.  Pilot plant trials were conducted to treat 14 tonnes of calcines to confirm the results before plant operations were implemented.

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