Rhodium in catalytic converters and other uses

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Uses for Rhodium

Rhodium is used to make electrical contacts, as jewelry and in catalytic converters, but is most frequently used as an alloying agent in other materials, such as platinum and palladium. These alloys are used to make such things as furnace coils, electrodes for aircraft spark plugs and laboratory crucibles.

History of Rhodium

Rhodium was discovered by William Hyde Wollaston, an English chemist, in 1803 shortly after his discovery of the element palladium. He obtained rhodium from a sample of platinum ore that was obtained from South America. After removing the platinum and palladium from the sample, he was left with a dark red powder. The powder turned out to be sodium rhodium chloride (Na3RhCl6·12H2O). Wollaston obtained rhodium from the powder by treating it with hydrogen gas (H2). Rhodium tends to occur along with deposits of platinum and is primarily obtained as a byproduct of mining and refining platinum. Rhodium is also obtained as a byproduct of the nickel mining operation.

Extract from: http://education.jlab.org

 

Rhodium, together with ruthenium, palladium, osmium, iridium, and platinum form a group of elements referred to as the platinum group metals (PGM).

It is lustrous and silvery white in colour. Rhodium has a higher melting point and lower density than platinum. It has a high reflectance and is hard and durable. Upon heating it turns to oxide when red and at higher temperatures turns back to its element. Rhodium is unaffected by air and water up to 600 C. It is insoluble in most acids, including aqua regia, but is dissolved in hot concentrated sulfuric acid and it is attacked by molten alkalis.

Applications

Most metal (85%) goes into catalytic converters for cars. The major use of the metal is in alloys with platinum and iridium. Which gives improved high-temperature strength and oxidation resistance. These alloys are used in furnace winding’s, pen nibs, phonograph needles, high-temperature thermocouple and resistance wires, electrodes for aircraft spark plugs, bearings and electrical contacts.
The metal itself is used to plate jewelry and the reflectors of searchlights, due to its brilliance and resistance to tarnish. It is also a highly useful catalyst in a number of industrial processes.

Health effects of rhodium

Rhodium compounds are encountered relatively rarely by most people. There are almost no reported cases of human being affected by this element in any way. All rhodium compounds should be regarded as highly toxic and as carcinogenic. Compounds of rhodium stain the skin very strongly.

Flammable. Dust explosion possible if in powder or granular form, mixed with air. Reacts with oxygen difluoride causing fire hazard.

Routes of exposure: The substance can be absorbed into the body by inhalation of its aerosol.

Inhalation risk: Evaporation at 20°C is negligible; a harmful concentration of airborne particles can, however, be reached quickly when dispersed.

Health effects of exposure to the substance have not been investigated. Insufficient data are available on the effect of this substance on human health, therefore utmost care must be taken.

Environmental effects of rhodium

Do not allow the material to be released into the environment without the proper governmental permits. Rhodium is too rare for the amount of it in soils or natural waters to be assessed. So its effect on the environment can be assumed to be nil. Tests on plants have shown that it is the least toxic member of the platinum group of metals.

To find out more about the pricing of Rhodium for extraction and recycling purposes. Please contact Vaslotrim so that we may assist with any questions.

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