AU-197 MOSSBAUER STUDY OF COPPER REFINERY ANODE SLIMES

Copper refinery anode slimes are abundantly produced during the electr olytic refining of copper. Although the slimes contain significant and economically recoverable amounts of gold and silver, the chemical sta te of the gold has not been fully identified. In the present work, the chemical form of gold in a copper anode, in a raw slime, and in slime s treated by different leaching procedures has been investigated by Mo ssbauer spectroscopy with the 77.3 keV gamma-rays of Au-197. The Mossb auer spectrum of the anode is typical of a dilute Au:Cu alloy. The spe ctrum of the raw slime consists of two components, namely, a single, r ather broad line with an isomer shift (IS) of about -0.3 mm/s relative to a Pt metal source and a quadrupole doublet with an IS of +1.2 mm/s and a quadrupole splitting of 5.0 mm/s. The single line component can be attributed to a gold-rich alloy, with an approximate composition o f Au60Ag40 or Au80Cu20 if it is a binary alloy, or to a ternary Au-Ag- Cu alloy of appropriate composition. The parameters of the quadrupole doublet match those of Ag3AuSe2 (fischesserite) or related Ag2-xAuxSe compounds. In these compounds, the gold atoms are coordinated by two s elenium atoms in a linear arrangement, as is typical for Au(I). It was found that the ratio between the concentrations of the metallic phase and the selenide strongly depends on the leaching conditions. The mea surement of the Lamb-Mossbauer factor of fischesserite is also reporte d.