Vale Inco Limited

Eric Devuyst

Mohamed Buarzaiga

Jean-Paul Raymond Duterque

Joe Paventi

Julian Edwards

Jean-Jacques Robert Perraud

A method and system of removing or decreasing waste liquor manganese concentration to less than about 1 mg/L total manganese without the precipitation of significant amounts of magnesium. The method and system include steps for treating the waste liquor using three separate circuits in which in the first circuit, manganese is reduced, for example, from about 2 g/L to &#x3c;500 mg/L using pH adjustment with a suitable neutralizing agent; and in the second circuit, the final target manganese level is achieved by oxidative precipitation using a suitable oxidizing agent. Part of the precipitated manganese product, e.g., MnO, is recycled to the oxidative precipitation circuit as seed and the balance proceeds to a third circuit wherein the precipitated manganese product is re-dissolved, and then recycled to the first neutralization circuit. In the first neutralization circuit and the second oxidative precipitation circuit, the process conditions are selected to minimize the precipitation of magnesium, e.g., Mg(OH).

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Stoney Creek, Canada

Eric Devuyst