User:Mattwells5/Platinum group

Production

Process flow diagram for the separation of the platinum group metals.

The production of individual platinum group metals normally starts from residues of the production of other metals with a mixture of several of those metals. Purification typically starts with the anode residues of gold, copper, or nickel production. This results in a very energy intensive extraction process, which leads environmental consequences. With Pt emissions expecting to rise as a result of increased demand for platinum metals as well as expanded mining activity in the Bushveld Igneous Complex, further research is needed to determine the environmental impacts. Classical purification methods exploit differences in chemical reactivity and solubility of several compounds of the metals under extraction. These approaches have yielded to new technologies that utilize solvent extraction.

Separation begins with dissolution of the sample. If aqua regia is used, the chloride complexes are produced. Depending on the details of the process, which are often trade secrets, the individual PGMs are obtained as the following compounds: the poorly soluble (NH₄)₂IrCl₆ and (NH₄)₂PtCl₆, PdCl₂(NH₃)₂, the volatile OsO₄ and RuO₄, and [RhCl(NH₃)₅]Cl₂.

Production in nuclear reactors

Main article: Synthesis of precious metals

Significant quantities of the three light platinum group metals—ruthenium, rhodium and palladium—are formed as fission products in nuclear reactors. With escalating prices and increasing global demand, reactor-produced noble metals are emerging as an alternative source. Various reports are available on the possibility of recovering fission noble metals from spent nuclear fuel.

Properties and uses

The platinum metals have many useful catalytic properties. They are highly resistant to wear and tarnish, making platinum, in particular, well suited for fine jewellery. Other distinctive properties include resistance to chemical attack, excellent high-temperature characteristics, high mechanical strength, good ductility, and stable electrical properties. Apart from their application in jewellery, platinum metals are also used in anticancer drugs, industries, Dental, electronics, and Vehicle Exhaust Catalysts (VECs). VECs contain solid platinum (Pt), palladium (Pd), and rhodium (Rh) and are installed in the exhaust system of vehicles to reduce harmful emissions, such as carbon monoxide (CO), by converting them into less harmful emissions.

Environmental Problems

It was previously thought that platinum group metals had very little negative attributes in comparison to their distinctive properties and their ability to successfully reduce harmful emission from automobile exhausts. However, even with all the positives of platinum metal use, the negative effects of their use need to be considered in how it might impact the future. For example, metallic Pt are considered to not be chemically reactive and non-allergenic, so when Pt is emitted from VECs it is in metallic and oxide forms it is considered relatively safe. However, Pt can solubilise in road dust, enter water sources, the ground, and in animals through bioaccumulation. These impacts from platinum groups were previously not considered, however over time the accumulation of platinum group metals in the environment may actually pose more of a risk then previously thought. Future research is needed to fully grasp the threat of platinum metals, especially since as more cars are driven, the more platinum metal emissions there are.

The bioaccumulation of Pt metals in animals can pose a significant health risk to both humans and biodiversity. Species will tend to get more toxic if their food source is contaminated by these hazardous Pt metals emitted from VECs. This can potentiality harm other species, including humans if we eat these hazardous animals, such as fish.

Platinum metals extracted during the mining and smelting process can also cause significant environmental impacts. In Zimbabwe, a study showed that platinum group mining caused significant environmental risks, such as pollution in water sources, acidic water drainage, and environmental degradation.

Another hazard of Pt is being exposed to halogented Pt salts, which can cause allergic reactions in high rates of asthma and dermatitis. This is a hazard that can sometimes be seen in the production of industrial catalysts, causing workers to have reactions. Workers removed immediately from further contact with Pt salts showed no evidence of long-term effects, however continued exposure could lead to health effects.

Platinum drugs use also needs to be reevaluated, as some of the side effects to these drugs include nausea, hearing loss, and nephrotoxicity. Handling of these drugs by professionals, such as nurses, have also resulted in some side effects including chromosome aberrations and hair loss. Therefore, the long term effects of platinum drug use and exposure need to be evaluated and considered to determine if they are safe to use in medical care.

While exposure of relatively low volumes of platinum group metal emissions may not have any long term health effects, there is considerable concern for how the accumulation of Pt metal emissions will impact the environment as well as human health. This is a threat that will need more research to determine the safe levels of risk, as well as ways to mitigate potential hazards from platinum group metals.