Rhodium Mining

Rhodium is a most rare metal among non radioactive metals found on earth. It occurs in natural alloys with other noble metals in iridosmine (11.25% Rhodium) and siserskite (4.5% rhodium)

Mining:

Even though rhodium occurs in natural alloys it is not used for the commercial Rhodium extraction. Commercial rhodium is extracted from the ores of copper sulfide and nickel as it comprises of rhodium and other platinum group metals with its ore. The copper and nickel ore containing rhodium are mined by surface mining and underground mining. The chalcocite and chalcopyrite are the ores which are mined mostly for extracting rhodium.

In surface mining, open cut mining method is handled. The surface is initially analyzed about the distribution of ores. The mines are dug as steps of wall for easy extraction of the ore. The ramps are built along the walls for the locomotion of heavy machineries, labors and transporting trucks. A pond is carved inside the quarry for storing of processed tailings and water waste. The pond is mostly poisonous as it may contain sulfur and radioactive disposals. It is the most effective and less economic method in mining of rhodium containing copper and nickel ores. It is safe and the rehabilitation of open pit mining is a easy and assuring process.

The underground mining is used in ore depth areas where the ores happens to be deep inside the earth's surface. It is employed only when the deep dug ores are premium in quality which can compensate the financial needs for the mining process. The main sources of ores containing rhodium are river beds of Ural Mountains in Russia, Sudbury at Ontario in Canada and majorly from South Africa.

Processing and extraction:

The collected ores of copper and nickel with Rhodium are milled and crushed into gangue. Then the crushed gangue undergoes the process of copper and nickel roasting, smelting and finally electrolytic refining for the removal of impurities. In the electrolytic refining, the noble metals such as gold, silver, platinum, osmium, rhodium, ruthenium and non metals such as selenium and tellurium are the impurities which settle down as anode mud inside the electrolytic cell.

The collected anode mud is the primary component for rhodium extraction. The anode mud is made to a liquid solution by adding sodium peroxide (Na2O2) with it. Then the mixture is now reacted with aqua regia or chlorine under concentrated hydrochloric acid, in which the usage scale for acid is based on the composition of anode mud mixture. After executing the reaction; gold, platinum and other non metals will be dissolved in the concentrated acid mixture leaving rhodium, osmium, iridium and ruthenium as a solid residue within it.

The solid residue is now treated with sodium bisulfate (NaHSO4) to separate rhodium from the mixture. The separated rhodium is then reduced under hydrogen to produce metal rhodium sponges. The sponges are later made into fine powder of rhodium metal by powder metallurgical process.Rhodium one of the costliest metal out there and its major producers are South Africa, Russia, Canada and Zimbabwe.

Definition:

Rhodium is a chemical component that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is create in platinum ores and is used in alloys with platinum and as a catalyst. It is abbreviated to Rh and has atomic number 45. It is one of the most expensive precious metals.

Properties:

Rhodium is a hard silvery white and tough metal that has a high reflectance. Rhodium metal does not usually form an oxide, even when heated. Oxygen is wrapped up from the atmosphere at the melting point of rhodium, but on solidification, the oxygen is released. Rhodium has both a higher melting point and lower density than platinum.

Application:

An electrical contact substance due to its low electrical resistance, low and stable contact resistance, and high corrosion resistance
The compound of a rhodium with BINAP gives a broadly used chiral catalyst for chiral synthesis, as in the synthesis of menthol.
It is also used as a filter in mammography systems because of the characteristic X-rays it produces.