PROCESSO PARA A RECUPERACAO DE METAIS VALIOSOS A PARTIR DE PIRITA IMPURA FINAMENTE MOIDA

The process is used for direct treatment of finely crushed impure pyrites or for treatment of the matte and dust-laden gas from smelting the pyrites with a non-oxidising gas at elevated temp. It comprises (a) (i) oxidising roasting of part of the pyrites or the matte, (ii) sulphatising roasting of the product with the rest of the pyrites or matte to produce sulphates of the metal values and iron oxide and (iii) leaching to produce a soln. contg. the metal values and an insoluble iron oxide residue used for iron prodn.; (b) separating the metal value-contg. dust from the gas and either (i) passing the dust to step (a) (ii) followed immediately by arsenic removal or (ii) subjecting the dust to a separate sulphatising roasting and leaching operation followed by disposal of the arsenic-contg. iron oxide residue; and (c) condensing sulphur from the gas. The process recovers Fe, Cu, Zn, Pb, Co, Ni, Cd, Ag, Au and S from impure pyrites (e.g. used for sulphuric acid prodn.) and iron matte (e.g. from arc melting of pyrites).