| Summary: | The reactivity of metallic palladium in a K2CO3-K2O-B2O3 melt is investigated as a function of heating temperature and time. The aqueous solubility of heat-treated palladium is enhanced by controlling the heating conditions leading to an optimum palladium extraction of 53% from the heat-treated product. The alumina crucible used as a reactor partially dissolves during the heating of metallic Pd, which requires the analysis of palladium solubilization to be discussed in terms of K2CO3-K2O-B2O3-Al2O3 system. Oxidized palladium combines with boron and aluminum oxyanions as ligands in the molten medium to form water-soluble palladium compounds. Information regarding water-soluble palladium compounds was obtained by analyzing the precipitate collected from the palladium-containing solution produced by water-leaching of the heat-treated product. The precipitate contained Pd (0.19 wt%), Al (0.74 wt%), B (2.6 wt%), and K (45 wt%). Raman spectroscopy confirmed the presence of oxidized palladium in the precipitate. Aluminum oxyanions with AlO4 and AlO6 structures and boron oxyanions as diborate groups also were detected in the precipitate.
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