RHODIUM
Latin name: Rhodium (Rh)
Group of chemical elements in the periodic table of Mendeleev: VIII
Atomic number: 45
Atomic mass: 102,9055
Density: 12,41 g / cm3
Melting temperature: 1963 ° C
Rhodium is a precious metal that belongs to the platinum group. It is a very rare and expensive element that is extracted from native platinum. A well-known property of the metal is its ability to break down certain substances into their simplest components in a gaseous state. It is known for its high chemical stability to aggressive environments: in this respect it surpasses many other elements.
Rhodium was discovered in 1804 by the British scientist William Heade-Woollaston shortly after his discovery of palladium.
Wollaston dissolved raw platinum in aqua regia and neutralized the excess acid with caustic soda. From the neutralized solution he covered platinum with ammonium chloride and palladium with mercury cyanide. The filtrate was treated with hydrochloric acid to remove the excess mercury cyanide and evaporated to dryness. The residue treated with alcohol turned out to be a dark red rhodium-sodium salt powder. The rhodium was recovered by heating this powder in a stream of hydrogen.
The name of the metal is derived from the Greek word "rhodon", which was named "rose" because of the pink color of its salts.
Rhodium: processing: 1 g powder, 1 g pressed cylinder, 1 g argon arc remelted pellet.
Sites, extraction methods
The largest reserves of rhodium there are today, Mexico (43%) is the frontrunner in terms of gold deposits, as its gold sands are oversaturated with rhodium. This is followed by the South African, Colombian and US supplies.
The annual rhodium production is 31 tons.
South Africa is the largest exporter of rhodium (80% by volume). The second largest production country is Russia (11,9%), followed by Canada and Zimbabwe.
Features
The extraction of rhodium from the obtained macro shafts is carried out in an artisanal way (mining). It is complicated by the composition of the ore: the metal is associated with gold, palladium, platinum and copper.
Production engineering
The production of pure metal is a complex process consisting of several stages.
The traditional method
is the cleaning of platinum stone and the extraction of the component rhodium.
The raw material is brought from the processing plant to the concentrator.
Here the valuable components and the "waste" are separated:
The ore is crushed and poured with water and chemical additives.
The mixture is saturated with air under pressure.
The foam floats and binds the platinum particles to itself.
It is skimmed off and dried.
The platinum content reaches 110-990 grams per ton.
The next step is metallurgy. The concentrated mixture is immersed in an oven and heated to 1500 ° C. The old rock is burned and the slag is removed by blowing it out. The concentrate content rises to 1400 g / ton. -
The final stage is the affination. Here the last platinum elements are removed from the rhodium in order to obtain 99,95% rhodium as the end product.
A solution left over from the platinum refining process is used to release the rhodium. After treatment with chemicals and incineration, the result is almost pure rhodium metal.
It takes five to six months from the transport of the ore from the site to the extraction of pure rhodium.
Rhodium from nuclear waste
Research is currently being carried out on several technologies in order, among other things, to recover rhodium from hazardous waste residues from nuclear power plants. These very cost-intensive new technologies enable a greater production potential of rhodium in the future than from conventional mining. Furthermore, problematic storage of nuclear waste would be reduced in this way.
Where is it used?
Despite its enormous price, the metal is in demand in more areas than it is extracted.
Manufacturing
Its properties have ensured that rhodium alloys are used in the most demanding applications, especially in catalysts:
- Iridium or platinum alloys are contained in precision instruments that can measure temperatures of up to 2200 ° C (for example in catalytic converters).
- Some crystals can only be grown in laboratories on platinum-rhodium filters.
- A platinum / rhodium alloy reduces the formation of nitric acid. Such an alloy is used to manufacture exhaust gas neutralizers for motor vehicles. The automotive industry is the main user of rhodium.
The second largest buyer of rhodium is glass industry.
Rhodium-platinum vessels, in which the fine threads are made, are used to melt the metal.
They are used to coat mirror surfaces and ultra-precision instruments. This is thanks to the fact that the surface reflects 80% of the light in the visible range of the spectrum and is not clouded by Superfine.
In radio technology, it is mostly not used for the manufacture of components because it is too brittle and unstable. Radio components are simply coated with rhodium. The contacts (reed relays) of the RPS 55 (A), for example, are coated with rhodium.
New generation material
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Rhodium metal is used as a component in laser mirrors and diffraction gratings.
The measurement of the neutron flux is made visible with detectors made with rhodium.
This electronics is developing into an important area of application. The metal is used in filters on LCD monitors (TVs, laptops, iPhones and other devices).
Jewelry
Silver band for engagement with gem for female Cropped of diamond luxury jewelery bijouterie ring from white gold or platinum with gemstone. 3D rendering on black background New collection of jewelry
The metal, along with gold, platinum and silver, is used to make jewelry and watches.
Jewelers appreciate the rhodium coating. Rhodium plating is a surface coating process with a fine-grain (0,11-0,26 mm) layer of rhodium.
Rhodium deposits are thinner than a human hair, but work wonders:
- Silver treated with rhodium begins to shine and becomes stronger. It does not tarnish or fade on contact with air.
- Platinum gets stronger, shines more.
- The surface of ordinary gold is given a prestigious platinum sheen. The product becomes finer.
- But that's not all of the advantages: Rhodium enables the production of white gold - for aesthetes - and black gold - for avant-gardists.
Precautions
The properties of the substance have been studied for practical use. The effects on human health and other biological agents have been partially studied.
It has been proven that rhodium compounds are highly toxic carcinogens. However, the amount of rhodium in certified jewelry is harmless to human health.
An alloy of rhodium and copper (or zinc), which is dissolved in hydrochloric acid, filtered and dried, results in a powder. This is because it is a compound that can detonate under normal conditions.
Prices
Rhodium is listed on the stock exchange along with gold, platinum and copper. It is the most expensive of the precious metals.
The global rush reached its peak at the end of 2008: At that time, up to 10.1k dollars per troy ounce were in demand on the foreign exchange market, which was ten times more than gold at the same time.
Then the market subsided and the price fell below a thousand euros.
In the last period (December 2019 - December 2020) the price per gram has tripled: from $ 150 to $ 500. In other words, the price was around $ 2021 for an ounce in December 14.100. The all-time high of rhodium was recorded in May 2021 at USD 29.100 per troy ounce.
As with other precious metals, the price of rhodium fluctuates. In the long term, however, it will continue to grow. Science, manufacturing and technology will not do without this metal. However, production capacities are limited and global deposits are finite.
Current rhodium price
