Perturbations from the recycled water chemical components on flotation of oxidized ores of copper—The case of bicarbonate ions

Recycling water in flotation of oxidized ores of copper can contribute to the environment and hydric resources safeguarding in the Katanga province of the Democratic Republic of Congo (DRC) through minimization of the release of pollutants to watercourses used as spillways of effluents. Recycling can also enable lowering the fresh water withdrawals to feed industrial processes. However, flotation of oxidized ores of copper and cobalt from the Luiswishi deposit using the process wastewater recovered from the New Concentrator in Kipushi (NCK) effluents has resulted in high recoveries of the gangue minerals at the expense of malachite and heterogenite. The same phenomenon has been observed when the NCK feed water is doped with bicarbonate ions. Based on the roughing flotation concentrate mineralogical analysis by means of the X-rays diffraction (XRD) and the scanning electron microscopy (SEM), it has been concluded that bicarbonate ions boost up the recovery of minerals from the gangue while depressing those bearing the metals of interest. As the matter of fact, bicarbonate ions provoke an increase in the pulp water dissolved oxygen (DO) content resulting in the reagents overconsumption through oxidation, the decrease in selectivity toward the minerals of interest along with the mechanical entrainment of the gangue minerals in the form of slimes in the concentrate leading to significant drops in the recoveries and grades of copper and cobalt. Instead, one has observed a marked presence of talc, chlorites and quartz in the concentrate as the content of bicarbonate ions was increasing in the feed water.