Since platinum is recovered from two platinum group metals minerals and metallic scrap, the performance of the overall recovery process is influenced by the electrowinning circuit performance. It is important to indicate that during the last ten years the platinum group metals have received special attention and some processes have been optimized. Once of them is the electrowinning of platinum. The usual metallurgical process starts with dissolution of platinum group metals, separation of ruthenium and osmium by a distillation procedure, separation of arsenic, selenium, tellurium and precipitation of precious metals. Basically, platinum group metals are removed by four consecutive solvent extraction separation circuits and the separated platinum strip solution is treated by a second solvent extraction stage for refining yielding chloroplatinic acid (H2PtCl6·6H2O) of high purity as strip solution, which is sent to the platinum electrowinning circuit.
The traditional procedure has been to produce a platinum sponge by pyrolysis of ammoniu-hexachloroplatinate or reduce potassium chloroplatinate. A new electrowinning cell developed by W.C. Heraeus employs a membrane, enhance the current efficiency. Also, there is no handling of platinum 4+ compounds, the potential problem of platinosis is reduced, the equipment does not need much area, explosion of hydrogen is minimum, more productivity, no extra-chemicals are needed. Although the initial investment is higher than the traditional process, the operating costs are reduced.
The main advantages of the membrane cell are that allow easy stripping of metal from the cathodes, sponge and ingot are obtained at the end of the process. During the electrolytic process, primarily produced powder shows high chemical activity due to its large superficial area and codeposition of platinum group metals such as platinum-rhodium or platinum-iridium is feasible and this condition enables short recycling circuits for any special function. It has been noted that the powder superficial area is very important aspect of the process and mainly for production of metallic platinum. It is possible to include other electrolytic process to recover rhodium and any other platinum group metal. The basic idea is to recover platinum group metals at lowest cost.