Introduction
Platinum-group metals (PGMs) are among the most valuable and important industrial metals today, due to their numerous and varied applications in fields ranging from the automotive industry to jewelry manufacturing. The interest in these metals is increasingly growing due to the growth of energy-oriented applications such as fuel cells and catalysis. The recovery of PGMs from complex secondary sources, where they are found as small particles, has been an important task in the mining industry for many years. One challenge of extracting PGMs from these secondary sources is to design efficient methods of separation and purification that can be economically viable. Selective precipitation of PGMs is a promising technique for achieving this goal.
Background
In selective precipitation, complex ores and wastewaters with varying concentrations of metals are mixed with different reagents in such proportions that the compounds of PGMs form precipitation compounds which can then be separated from the mother liquor. The technique is an inexpensive process since no expensive separation equipment is required, and compared to other metals, PGMs are less soluble in most reagents and more likely to precipitate selectively. However, the technique is limited by the dissolution rate of the metals, and the presence of other ions in the solution, which can limit the effectiveness of the process.
Recent research
Recent research has focused on improving the efficiency of selective precipitation methods for concentrating PGMs. For instance, researchers have examined various types of reagents, such as lead nitrate, potassium iodide, and ammonium thiocyanate, to determine the optimal combination of reagents and conditions for the precipitation of PGMs. In addition, other techniques such as reduction-precipitation and absorption-precipitation processes have been developed for complex secondary sources that contain very low concentrations of PGMs.
Conclusion
Selective precipitation is an effective and cost-efficient method for the recovery of PGMs from complex secondary sources. In recent years, much research has been conducted to improve the efficiency of the technique, with greater understanding of the conditions necessary for effective precipitation. The development of these processes has the potential to increase the amount of PGMs recovered from secondary sources and reduce the amount of waste generated from the extraction process.
