Leaching characteristics of palladium heat-treated in a molten K2CO3–K2O–B2O3–Al2O3 media

Abstract Water-soluble and dilute acid-soluble (0.01–1 M HCl (aq)) palladium compounds were generated by heating metallic palladium in a molten K2CO3–K2O–B2O3–Al2O3 media. Palladium was extracted from these compounds in the aqueous and acidic solutions with an extraction efficiency of 79–94%. The duration of heat-treatment was a key parameter affecting the solubility of the formed palladium compounds. Increasing the time decreased the amounts of the water-soluble compounds and increased the amounts of the dilute acid-soluble ones. In addition, changing the duration of heat-treatment also caused the structure of aluminum oxides in the palladium compounds to change from AlO6 to AlO4, thereby decreasing the water solubility. The duration also affected the boron to aluminum ratio in the acid-soluble palladium compounds, and the solubility of these compounds decreased with increasing proportion of boron, due to the formation of network structures such as metaboric rings and chains.