Hydrometallurgical recovery of platinum from catalytic converters

Abstract

With the developing technology and the improvement of environmental protection laws, the consumption amount of platinum group metals (PGM) is increasing significantly. Over the last decade, these metals have found more use in industrial applications and with the growth in the world population, the consumption amount of products that use these metals has also increased. In particular, the automotive industry has been the area where metals in this group are most needed, due to the increasing production capacity and the emission regulations that are being tightened day by day. In this study, the properties of platinum group metals, their usage area, applications in catalytic converters and recycling methods were investigated. Afterwards, using a scrap catalytic converter, Pt was recycled from the catalyst and the parameters which affect the recycling efficiency were optimized. During the selection of the recovery method and its operation, the minimum damage to the environment was taken into consideration. As a result of the experimental studies, the dissolution of Pt was achieved by heat treatment of the leach solution prepared with 4.5M HCl (14.4%), 12.5% H2O2, 40/1 solid-liquid ratio at 75 °C for 90 minutes, with a recovery rate of 91.12%. In the precipitation experiments, the reduction of Pt to the metallic form is obtained with 0.079 mol NaBH4 which was mixed with the solution prepared under the best leaching conditions. Also, this solution was heat treated at 65 ℃ for 60 minutes, and the precipitation efficiency of 97.88% was achieved. As a result of the serial experiment, within the scope of the thesis, a simple and environmentally friendly hydrometallurgical method was developed for the recovery of Pt from catalytic converters; that have completed their useful life. Ultimately, 89.19% of Pt was recovered by optimizing the experimental parameters in the dissolution and precipitation experiments.