A general overview of the element platinum

Abstract:

Introduction:

The purpose of this report is to describe and detail the findings of my research into the metal platinum. The first section of this report will investigate the chemical, physical, mechanical and thermal properties of platinum. The second section will cover the various methods of how platinum is produced, and it’s uses in industry. The third and final section of this report will analyse the health and safety implications platinum can cause to the body, and a brief overview of the environmental impacts.

The properties of platinum

Platinum is a very dense and heavy material, but it is also quite soft, malleable and ductile. Platinum has a melting point higher than most other metals. Platinum is also considered a noble metal due to how unreactive it is. Platinum is fairly resistant to acids and will not oxidise in air, so it will not tarnish or rust.

    Chemical properties:

CAS number

6/4/7440

Thermal neutron cross section

9 barns/atom

Electrode potential

1.2V

Ionic radius

0.650Å

Electronegativity

2.2

X-ray absorption edge

0.1582 Å

Electrochemical equivalent

1.816g/A/h

 (Å=10×10-10)

   Physical properties

Density

21.45g/cm3

Melting Point

17690C

Boiling Point

38250C

    Mechanical properties

Tensile strength

125-165 MPa

Modulus of elasticity

171 GPa

Bulk modulus

230 GPa

Shear modulus

62 GPa

Poisson’s ratio

0.39

Elongation at break

35%

Hardness, Vickers

40

    Thermal Properties

Thermal expansion co-efficient (@200C/680F)

9.10 µm/m0C

Thermal conductivity

69.1 W/mK

Platinum production and it’s uses in industry

Platinum is usually found from ores of elements such as nickel and copper during mining of those materials but can also be found in placer deposits. Platinum will usually be found with several impurities which we do not want and must separate the platinum from. One method that can be used to remove the impurities from the mixture is to take advantage of platinum’s density by adding a liquid which will allow the impurities to float away. Platinum being very unreactive can be mixed with hydrochloric and sulphuric acids and will not react whereas many other substances will react. The remaining mixture can then be filtered to separate the impurities and the platinum. Platinum in its raw form (Platinum and all other platinum group metals) can be purified with aqua regia (1:3 mix of nitric and hydrochloric acid), which causes platinum, gold and palladium to be dissolved removing them from the other platinum group metals. The gold must then be separated next by precipitating it will Iron(II) Chloride and filtering the gold away. The platinum can then be precipitated away by adding ammonium chloride to produce a precipitate of ammonium chloroplatinate. This will then be filtered away and heated to obtain platinum.

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The industry that most heavily uses platinum is the automotive industry which uses it as an auto-catalyst. In the exhaust system of a truck or car, a fine coating of platinum will be present to act as a catalyst to speed up the reaction between O2, CO and other hydrocarbons to produce CO2 and H2O. Having this coating of platinum will also reduce the number of sulphur particles output into the atmosphere. The Chemical industry uses platinum as a catalyst also to increase the rate of reaction of a given reaction and to reduce its activation energy, savings costs for the manufacturer.  The most notable use of platinum as a catalyst is in the production of nitric acid. However, the greatest demand for platinum in the chemical industry comes from the production of speciality silicones. Platinum compounds are used in a large variety of materials from electrical wire insulation to lubricants. The electronic industry made use of platinum as platinum was coated onto the platters used in HDDs as platinum enabled data storage. However, SSDs have become more common today and therefore the use of platinum in the electronic industry has decreased. The glass manufacturing also employs the use of platinum due to its ability to withstand temperatures of 1700 0C. Also, platinum will not react with the materials and silicates used in the manufacture of glass. For 40 years the petroleum industry has used platinum as a catalyst in cracking longer hydrocarbon chains into smaller, more useful ones such as diesel and kerosene. In the medical industry, platinum is used in all pacemakers and in other medical devices such as defibrillators and stents. Platinum is the material of choice here due to its unreactive nature. However, platinum also has anti-cancer potential with cisplatin drugs being produced commercially since the 1970s.

Health and safety implications of platinum

The toxicological effects of platinum in humans are limited to the complex halide salts and the antitumor agent cis-platin and similar compounds of cisplatin. These compounds are some of the most potent sensitizers known. Workers exposed to these compounds showed symptoms of itching, watering of the eyes, repeated sneezing, rhinorrhoea (runny nose), chest tightness, wheezing, shortness of breath, cough and cyanosis. Some workers even developed scaly erythematous dermatitis with urticaria (hives). The development of symptoms after exposure to these platinum compounds has ranged from a few weeks to several years. However, the longer the exposure the more severe the symptoms and the longer they will generally last. The most potent compounds of these complex halide salts are hexachloroplatinic acid and the chlorinated salts ammonium hexachloroplatinate, potassium tetrachloroplatinate, potassium hexachloroplatinate and sodium tetrachloroplatinate. Ammonium chloroplatinate is formed in the separation of platinum and palladium before being heated to give platinum.

With platinum being heavily used in the automotive industry to reduce greenhouse gas emissions very little consideration has been paid to the possible effects of platinum emissions in exhaust systems to the public. A small study with only 3 test subjects who were highly sensitive to platinum salt concentrations, were tested using particulate exhaust samples where concentration exceeded 5 µg/ml, which is normally enough to evoke a response. All test subjects failed to show a positive response. This is most probably due to the platinum emissions being metallic and not in salt form.

Cisplatin which is used in cancer chemotherapy has caused nephrotoxicity with both tubular and glomerular lesions, severe nausea and vomiting, ototoxicity with tinnitus and hearing loss, and sensory peripheral neuropathy. Carboplatin can also be used as it is less nephrotoxic it has induced bone marrow suppression.

References:

CLEARE, M.J. Immunological studies on platinum complexes and their possible relevance to autocatalysts. In: Proceedings of the International Automotive Engineering Congress and Exposition, Cobo Hall, Detroit, 28 Feb.–4 March 1977. Detroit, MI, Society of Automotive Engineers, 1977 (SAE Report 77061).