Platinum is used as a catalyst material in a variety of industrial processes. Because of the increased interest in renewable energy sources, there is also a high demand for platinum in technologies such as fuel cells and batteries. In the future, the secondary production of this resource will become more relevant from an economical and environmental point of view.
To guarantee sufficient purity of the platinum, several dissolving, separation, and calcination steps are necessary. This process cycle must be repeated until sufficient purity is reached.
Conventionally, platinum-sal-ammoniac1 is calcinated at 800 °C for 24 h in a resistively heated oven. During this step, a platinum sponge is formed. Using microwave technology, we were able to improve this energy-intensive procedure. The main improvements was the shortening of the heating-up period as well as the holding time. In addition, due to its highly flexible process control, the MW treatment also showed a positive impact on the morphology of the platinum sponge.
In order to make the platinum sponge highly soluble, its temperature should be as high as possible. But with increasing platinum temperature, the solubility of chlorine in the hydrochloric acid decreases, which slows the reaction rate. By selectively heating the platinum with microwaves, it is possible to reach the necessary temperature without the unwanted heating of the surrounding solution. Depending on the quality2 of the microwave radiation, the dissolution rate of platinum was nearly doubled.
former Argillon GmbH
Activities: Process development and optimization
1 During upstream process steps the platinum is separated from other metals and converted into (NH4)2[PtCl6] by different leaching processes.
2 The solution rate of the platinum sponge is highly dependent on the quality of the introduced microwave radiation. A continuous exposure to MW radiation leads to a more homogenous temperature of the sponge. Treatment with pulsating MW, however, leads to the intended effect of localized overheating.