Dissolution Behavior of Platinum in Na₂O–SiO₂-Based Slags

Abstract

With the aim of minimizing the loss of platinum into slags by controlling the slag composition during the high-temperature recycling process, the effects of representative slag components, namely, Al₂O₃, MgO, Fe₂O₃, and CuO_x, on the dissolution behavior of platinum into Na₂O–SiO₂-based slags were investigated. The solubility of platinum in the slags was measured by equilibrating the Na₂O–SiO₂-based slags with pure solid platinum at 1473 K in air. The dissolution of platinum in the slags was found to be suppressed by the addition of Al₂O₃, MgO, and Fe₂O₃. Al₂O₃ and Fe₂O₃ behaved as acidic oxides, whereas MgO behaved as a diluent and decreased the solubility of platinum in the slags. CuO_x behaved as a weakly basic oxide and slightly enhanced the dissolution of platinum into the slags. The correlation between the platinate capacity of the slag, which is a parameter proposed in this paper, and the optical basicity enabled the content of platinum in slags at 1473 K to be estimated from the slag composition.