Recovery of platinum, paladyum and rhodium from spent catalytic converters by hydrometalugical way

The reason for catalytic converters is to minimize harmfull gases that release out from cars' exhaust system. After burns the mixture of air and gasoline or diesel in the combustion engine is converted to carbondioxide (CO2), water (H2O), carbonmoxide (CO), nitrogenoxide (NOx) and hydrocarbon (HC). CO, NOx and HC are harmfull gases for the human health and nature. The reason to use catalytic converters is to convert these harmfull gases to harmless form. Platinum, palladium and rhodium are used as a catalysor in catalytic converters. Recovery of platinum group metals (PGM) has been attractive in recent years since both environmental and economic consequences. In this study, the methods of PGM recovery including hydrometallurgical method from scrap catalytic converters were examined. Furthermore detailed physical and chemical characterization of the spent catalytic converters were carried out. The components of catalytic converters were analysed by XRD method and the quantity of the materials such as platinum, palladium and rhodium were analysed comparatively by using AAS and ICP-MS techniques. The new alternative method was proposed including the addition of HNO3 as an oxidant agent, which implied the reduction of the pollutant gases and also the environmental impact of the chemical process. The final reagent composition which was proposed contained the mixture of 60 ml of HCl, 60 ml of HNO3, and the leaching temperature was at 75 ˚C for 45 min, 5 grams of sample with a previous thermal pre-treatment at 700 ˚C during 1 h of the sample. With this treatment 99 % of the both platinum and palladium and 47 % rhodium present in spent catalytic converters could be recovered. Recovery efficiency from the solution of platinum, palladium and rhodium by using alüminyum to precipitate is also 99%.