Aiming to optimize rhodium recovery in the high temperature recycling process
by minimizing rhodium loss into slags in an oxidizing atmosphere by
controlling slag composition, the effects of representative slag components,
such as Al2O3, MgO, and CuOx, on the dissolution behavior of rhodium into the
Na2O-SiO2 slags was investigated. The solubility of rhodium was measured by
equilibrating the sodium silicate based slags with pure solid rhodium at 1473
K in air. Considering that rhodium dissolved into slags as RhO1.5, the effect
of the oxide addition on the activity coefficient of RhO1.5 in slags was
determined. The dissolution of rhodium in slags was suppressed by the
addition of Al2O3 and MgO, where Al2O3 behaved as an acidic oxide and MgO
behaved as a diluent of slag basicity at a fixed Na2O/SiO2 ratio of 0.97. The
content of copper in solid rhodium equilibrated with the CuOx bearing slags
slightly increased with increasing content of CuOx, and CuOx was found to
slightly enhance the dissolution of rhodium. Rhodate capacity of all slag
systems increased with increasing optical basicity, suggesting that the
correlation between rhodate capacity and the optical basicity enables the
estimation of the content of rhodium in slags of which thermodynamic
properties of rhodium are not clarified.
Interionic Interactions, Electronic Polarizability and Optical Basicity of Oxide Glasses.
