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Occurrence
Hafnium is a rare metal that only occurs in small quantities in the earth's crust. Unlike many other metals, it rarely forms its own deposits. Instead, it almost always occurs together with the chemically very similar element zirconium. Both elements are mainly found in the mineral zircon, which is contained in certain sand deposits.
Important zircon deposits are located in Australia, South Africa and the USA, among other places. Hafnium is produced exclusively as a by-product of zirconium refining, as both elements always occur together in zircon. These countries are therefore also the most important sources of hafnium. How much hafnium is extracted therefore depends heavily on how much zirconium is produced. However, even the US Geological Service does not have current data on global primary production or hafnium reserves.
Extraction
The production of hafnium begins with zircon sand, from which zirconium compounds are first extracted. As hafnium and zirconium are chemically very similar, their separation is technically demanding and requires several processing steps.
First, the mineral is chemically digested to create a solution that contains both zirconium and hafnium. The two elements are then separated from each other using special chemical processes. Processes such as solvent extraction or ion exchange are often used for this.
The hafnium obtained is then further processed, usually using a compound called hafnium tetrachloride. In the so-called Kroll process, metallic hafnium is produced by reduction with magnesium. For particularly high purity requirements, this is then purified using the zone melting process: In this process, a narrow melting zone is slowly passed through an elongated hafnium rod, whereby impurities migrate into the liquid phase and accumulate at the end of the rod. In this way, purity levels can be achieved that are required for applications in nuclear technology and the semiconductor industry.
The global demand for germanium is increasing. In view of the high concentration of extraction and further processing, recycling is becoming increasingly important as a source of this raw material. This also applies to the processing of scrap from the production of germanium-containing products. In Europe, the Critical Raw Materials Act stipulates that 25 percent of the demand for strategic raw materials must be obtained through recycling by 2030. Germanium is one of these materials. Alongside others, the raw materials trader TRADIUM is already working at national and international level to exploit the potential of this raw material source.
