Malachite and heterogenite behavior during the locked-cycle recycling of process water in flotation of copper-cobalt oxide ores

The behavior of malachite and heterogenite was investigated during the process water recycling in flotation of copper-cobalt oxide ores from the deposit of Luiswishi located in Haut-Katanga province (DRC). A synthetic mill wastewater (SMWW) was utilized as feed water alone and in mixture with water recovered from the flotation tails in view to achieve at the laboratory scale the locked-cycle recycling of the industrial mill wastewater (IMWW). To simulate the chemical species presence in the pulp water and their effects on the flotation of malachite and heterogenite, calcium, magnesium and bicarbonate ions were added to the feed water and the recoveries of copper and cobalt followed during the roughing flotation stage. The concentrate XRD and SEM analyses together with the floated minerals microanalyses by EDX spectroscopy, leaching tests of mono-minerals followed by the Pourbaix diagrams construction and DRIFT spectroscopic analyses, have enabled identifying changes in the surface properties of malachite and heterogenite and describing their behaviors. It was concluded that the locked-cycle recycling of process water is inducing the build-up of chemical species in the pulp, which favors the exaggerated dissolution and hydration of malachite and heterogenite interfering on the recovery of copper (40%) and cobalt (58%) with a significant drop in their concentrate grades (7.3% Cu and 2.7% Co). The deterioration of the concentrate characteristics results also from the gangue minerals entrainment. A better description of the valuable minerals behavior in the SMWW presence could enable designing strategies in view enhancing their floatability during the locked-cycle recycling of water.