Abstract
Under specific controlled conditions, the addition of SO 2 to oxygen or air produces the peroxy-monosulphate free radical in solution, which is a stronger oxidant than oxygen alone. In this study, the practical strategies required to optimise the oxidation of Fe(II) with SO 2/air was investigated at 75 °C as part of a process to remove iron as Fe(III) oxides from a synthetic nickel laterite high pressure acid leach solution containing 5 g/L Fe(II), 1 g/L Fe(III), 8 g/L Ni, 30 g/L Mg in sea water at pH about 2. The rate of Fe(II) oxidation was optimised in the pH range of 1.2–2.0 with respect to SO 2/air ratio and gas flow rates for minimum production of H 2SO 4 and maximum utilisation of SO 2. In order to minimise the air flow rates into the reactor vessel, the maximum rate of SO 2 addition that could be employed with air was established whilst maintaining oxidising conditions. The results provide strategies for commercial applications of the SO 2/air oxidising system and indicate important factors for reactor design.
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