THERMAL-TREATMENT OF COMPLEX SULFIDE ORES IN N2 AND H-2 ATMOSPHERES - A NEW APPROACH FOR THE EXTRACTION OF THEIR VALUABLE ELEMENTS

The thermal treatment of natural sulfidic minerals such as sphalerite, galena, chalcopyrite, and pyrite in an N-2 or H-2 atmosphere was studied to examine the nature of reactions taking place. Such treatments have the potential of avoiding sulfur dioxide production which is associated with the roasting of complex sulfide ores (CSOs). The thermal treatment of CSO concentrates at temperatures less than 1000-degrees-C in a nitrogen atmosphere leads to the decomposition of the pyritic matrix to pyrrhotite and the volatilization of sulfur, galena, and some of the CSOs' trace elements. Treating the CSO in a reducing atmosphere converted sphalerite to zinc and produced a solid containing Cu-degrees, Fe-degrees, and silicoaluminates. Selective dissolution of copper may be achieved by a hydrometallurgical process. Hydrogen sulfide could be reacted with pyrrhotite to form pyrite and hydrogen. A flow sheet is proposed.