| 英文摘要 |
The target of this project is to develop a hydrometallurgical method to recover valuable metals, which include platinum, palladium and rhodium, from spent automotive catalysts. In this project the spent automotive catalyst was ground for 10 minutes until about 96% of the particle size was less than 0.84mm, the remainder was between size 0.84mm – 0.297mm. The metal content of the final sample of the spent automotive catalyst for platinum, palladium and rhodium is 669 mg/kg, 240 mg/kg and 26.3 mg/kg respectively.Composition analysis for the sample for water content, ash content, combustible content and density for this sample is approximately 0%, 99.39, 0.61 and 2.5 respectively. Results from this project revealed the optimum leaching conditions in hydrochloric acid impregnation for the recycling of platinum, palladium and rhodium are: 10N hydrochloric acid heated to 70oC for 5 minutes with a solid-liquid ratio of 1g/50mL, with 2,000 times the theoretical value of H2O2. Under these conditions platinum and palladium can be recovered at 100% efficiency and rhodium can be recovered at58.21% efficiency.
The optimal laching solution with sodium hydroxide or ammonia solution to adjust the pH is not effective for the recovery by precipitation of platinum, palladium or rhodium. The precipitation of optimal laching solution between ammonium chloride, sodium chloride and calcium chloride was ammonium chloride, which resulted in recovery of platinum, palladium and rhodium precipitates with less that 50% precipitation. Also, the replacement of optimal laching solution using zinc plate and iron plate was unsuccessful to reach platinum, palladium and rhodium metal separation. The optimal laching solution can obtain the crystallization product. The enrichment of platinum, palladium and rhodium metal content of crystallization product is approximately 10.73, 8.91 and 7.59 times respectively. Therefore, this study suggests that the best recovery process is ground scrap car catalyst to below 50mesh sieve, react with 10N hydrochloric acid with a solid liquid ratio of 1g/50ml, 70oC for 5 minutes. Leaching of 100% platinum, 100% palladium and 58.21% rhodium can be achieved and impregnated into solution. Then this optimal laching solution can be crystallized to enrich platinum, palladium and rhodium metal.
|