Behavior of platinum in the system of the matte-slag in the processing of copper-nickel materials

Abstract

Copper-nickel sulfide ores are one of the main sources of platinum. One of the ways to extract precious metals from such ores involves melting of a concentrate in electric ore smelting furnaces, where the melt is divided into matte and slag. Platinum is generally concentrated in matte; however, some its part remains in the slag, thus leading to metal losses. In order to reduce platinum losses, the forms of platinum in these phases should be studied. It was found that during the melting of this ore, iron, nickel, and copper are reduced. The mineral composition of matte has been studied. Platinum in matte is present in the form of intermetallics with Fe and Ni. The PtFe intermetallic is a dispersed needle formation with a length of 20 to 500 ?m and a thickness of up to 10 ?m. The size effect is revealed: the content of platinum in the PtFe intermetallic decreases with decreasing the thickness of needle formations. The decreases in the content of platinum in dispersed needle formations can be explained by an increase in the thermodynamic activity and changing properties of the dispersed substance and a corresponding increase in solubility. It was found that matte drops, together with their associated platinum-containing particles of no more than 5-7 ?m in size, were carried into the slag by gas bubbles using flotation. The conditions for the rise of a matte drop, together with a bubble in the slag, consist in the fact that the adhesive force of the drop with the bubble and the buoyancy force acting on the bubble must be greater than the gravity of the drop.

INFLUENCE OF CaF2 AND CaCO3 FLUX ADDITIVES ON THE DISTRIBUTION OF GOLD AND PLATINUM BETWEEN MATTE AND SLAG DURING MELTING OF COPPER-NICKEL SULPHIDE MATERIALS

“…The main reason for the loss was the flotation of matte droplets containing gold and platinum by gas bubbles that appear as a result of the decomposition of sulphides during the melting of copper-nickel sulphide materials [5]. From the point of view of physical chemistry, flotation means the floating of bodies of higher density than a liquid on its surface under the action of interfacial tension forces.…”

“…Calcite releases large amounts of CO2 gas when heated. Despite the fact that gas bubbles lead to the removal of gold-and platinum-containing sulphide droplets from the matte melt into the slag [5], they also contribute to the enlargement of dispersed droplets in the slag. CaO formed during the decomposition of calcite lowers the melting point of the slag and its viscosity.…”