Preparation of Co3O4 from a leaching solution of cobalt-rich slag by ozonation

Abstract

Cobalt-rich slag from blister refining is leached with an oxidising acid, and Co3O4 powder is prepared by an ozonation–precipitation–calcination method after iron has been removed from the solution by the goethite process at different pH values. The effects of stirring speed, gas flow rate, ozone concentration, pH and solution temperature on the precipitation rate of cobalt are investigated. The solution pH has an obvious effect on the precipitation rate, as do the stirring speed, gas flow rate and ozone concentration, but the temperature has little effect. With almost all the cobalt precipitated from the solution, the losses of copper and zinc are about 10% and 1·5%, respectively. The cobalt is precipitated in the form of amorphous CoOOH, identified by X-ray diffraction and with some physicochemical properties similar to those of cobalt hydroxide. The amorphous CoOOH is transformed into spherical Co3O4 powder by the calcination treatment.