Platinum group metals include platinum (Pt), palladium (Pd), osmium (Os), iridium (Ir), ruthenium (Ru), and rhodium (Rh). They are all well known for their special properties and scarce resources. Because of their wide application to modern industries and sophisticated techniques, they are called "modern noble metals". The world's output of platinum group metals has made successive strides during the past few decades: topped 100 tons in 1969, doubled in the late 1980s to reach 200 tons (Zhang Wenpu, 1997), and approached to 300 tons in the 1990s. These figures manifest the far-reaching significance of the so-called "modern noble metals".
After placer platinum deposits were discovered in 1778, mining was mainly carried out by such countries as Columbia and Russia for a short time. In the late 19th century a large-sized primary platinum deposit was found in Canada and in the 1920s South Africa discovered the Bushveld deposit. Then primary platinum began to gradually take the place of placer platinum. After the former USSR found the Norilsk Pt deposit and the USA explored the Stillwater Pt deposit in the 1960s, platinum placer was completely replaced by primary platinum. Since then Russia, South Africa and Canada have been the three leading countries in the world in terms of the reserves of platinum-bearing ores and the output of platinum group metals.
China is one of the countries in great shortage of platinum group metals. The mining of placer platinum deposits started as early as the end of the Qing Dynasty, but the output and scale are too small to be mentioned. Even until the 1950s platinum mining was carried out only in one or two placer mines. It was not until the Jinchuan platinum-bearing Cu-Ni sulfide deposit was found and a nickel electrolytic workshop went into operation in 1996 that the production of platinum group metals had changed its backward face. In the 1970s, some small platinum-bearing orebodies were discovered and low-grade platinum-bearing ores, polymetallic ores and porphyry copper ores were first used to recover platinum group metals. Although geological and geochemical researches have been conducted on platinum since the 1970s and recovery of platinum group metals has been used since the 1980s, the production of platinum group metals was far from meeting the demands because no breakthrough was made in prospecting. Therefore, the imbalance between supply and demand can only be mitigated through import.
The six elements of the platinum group have similar physical and chemical properties and also some distinctive characteristics on the other hand. Owing to their high melting points, high strength, stable electrical and thermal properties, high resistance to electrical spark loss, corrosion and oxidation under high temperatures, and fine catalytic activity, the platinum group elements have found a wide range of applications. They were mainly used for making jewelry in early days. After the 1950s, such metals have been widely applied to chemical, automotive, aviation, glass, atomic, petroleum and petrochemical industries, environment protection, manufacturing of sensors, electronic, electrical and medical devices, handicrafts and coins. These metals are indispensable in those applications though only small quantities are needed in general, thus called "industrial vitamins". The major applications at present are automotive industry and production of catalysts. In 1996, 35.5% and 28% of the total consumed 143 tons in the world were used for these two purposes respectively. The amount of noble metals used for purifying automotive tail gas had the most rapid increase. In 1993, 53,000 kg of platinum, 22,000 kg of palladium and 11,000 kg of rhodium were consumed for this purpose. The first two make up 50% of the respective total consumption and the last accounts for 90% of the total rhodium consumption of the same year. Research has been conducted in recent years to develop relatively cheap palladium-bearing catalysts to replace platinum-palladium-rhodium catalysts.