Rhodium: Encyclopedia II - Rhodium - Occurrence

Rhodium - Occurrence

The industrial extraction of rhodium is complex as the metal occurs in ores mixed with other metals such as palladium, silver, platinum, and gold. It is found in platinum ores and obtained free as a white inert metal which it is very difficult to fuse. Principal sources of this element are located in South Africa, in river sands of the Ural Mountains, in North and South America and also in the copper-nickel sulfide mining area of the Sudbury, Ontario region. Although the quantity at Sudbury is very small, the large amount of nickel ore processed makes rhodium recovery cost effective. Main exporter of rhodium is South Africa (>80%) followed by Russia. However, the annual world production of this element is only about 20 tons and there are very few rhodium minerals. Moreover, it is generally difficult to determine if a rock sample does or does not contain platinum group elements. As of 2006, rhodium cost approximately six times as much as gold, by weight.

It is also possible to extract Rhodium from spent nuclear fuel, which contains an average of 400 g per metric ton of Rhodium. Rhodium produced in such a way contains radioactive isotopes with half-lives of up to 2.9 years and is therefore stored at least 20 years in a secured area to allow it to become stable. Every 2.9 years of isolation reduces the radioactivity by 50%. Fission Rhodium has a specific activity of 8.1 curies of radioactivity per gram after 5 years isolation. Under health physics safety rules any isotope that emits more than 1 ci of activity is a hazard however after 8 years the activity falls to 4.1 ci, after 11 years it is 2.2, after 14 years 1.1, after 17 years .55 ci ans after 20 years only .27 ci. After 30 years the activity falls to 2.702E-4 ci, which is under the threshold for low level risk by even the most stringent health physics rules. The radioactivity of Rhodium falls off so quickly because the percentage or Rh-102 in the recovered Rhodium is only a trace amount and the remainder of the material absorbs the energy released. Rhodium averaged $26.43 per gram or $1,000.00 per troy ounce over the last 30 years and $2900.00 per troy ounce in December 2005, adding significantly to the resource value of reprocessed fission waste.

Adapted from the Wikipedia article "Occurrence", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki