Abstract
In the dental laboratories, powdery waste containing precious metals such as gold (Au) , silver (Ag) and palladium (Pd) is generated during the polishing process of dental alloy. For the recovery of precious metals, powdery waste is treated by dissolution with nitric acid and / or aqua regia. Similar wastes containing precious metals are also treated in copper smelting process as secondary resources. In general, the precious metal content of powdery waste is less than 1%, and therefore, it is difficult to economically and technologically recover these precious metals in the conventional process. In this research, a separation and recovery method using flotation was investigated. It was observed that selective recovery of the precious metals from powdery dental waste was obtained giving; 87.4% Au, 90.3% Pd and 88.5% Ag in a two stage flotation using sodium isopropyl xanthate (SIPX) as a collector. In addition, the values of enrichment of precious metals obtained by 1st flotation and 2nd flotation were 9.2-9.6 and 8.1-8.3 respectively. According to the series of these experiments, it was found that precious metals are effectively concentrated from the powdery dental waste. Therefore, we suppose this flotation process to be useful for the improvement of conventional recycling process.
