Rhenium: A Pioneering Element

Rhenium (chemical symbol Re), the 75th element in the periodic table, is a unique and fascinating element with a rich history, diverse distribution, and significant applications in various fields. Named after the Latin term Rhenus, signifying the Rhine River, Rhenium was the last naturally occurring stable-element discovered, followed by radioactive elements with no stable isotopes like technetium and plutonium¹.Although the production of rhenium has gradually increased with the development of industry, its scarcity still results in high costs. Even so, some cutting-edge industries, such as aerospace, still use rhenium to manufacture components of aircraft engines.²

Discovery

Dmitri Mendeleev, the creator of the periodic table, had predicted the existence of Rhenium. In 1914, British physicist Henry Moseley calculated some data about this element, further substantiating its potential existence³.

The final discovery of Rhenium was made by Walter Noddack, Ida Noddack, and Otto Berg in Germany in 1925. They claimed to have detected this element in platinum ores and niobium-iron ores. Later, they also found Rhenium in beryl-silicon-yttrium ore and molybdenite. In 1928, they managed to extract 1 gram of Rhenium from 660 kilograms of molybdenite⁴. By 1968, it is estimated that 75% of Rhenium in the United States was used in scientific research and the production of refractory metal alloys⁵.

Interestingly, in 1908, Japanese chemist Masataka Ogawa announced the discovery of element 43, which he named Nipponium (Np) in honor of his home country, Japan. However, later analysis pointed out that what he discovered was actually the 75th element, Rhenium, not 43 (technetium). Today, Np is the chemical symbol for the 93rd element, neptunium, named after Neptune⁶.

Distribution and Existence

Rhenium is rare, with its content in the Earth's crust estimated to be 0.001x10^4%. It is scattered in molybdenite, rare earth ores, and niobium-tantalum ores, all in low concentrations. In molybdenite, it may exist as Rhenium disulfide (ReS2) or Rhenium heptasulfide (Re2S7). Rhenium has two natural isotopes: Re-185 is stable, and Re-187 is radioactive⁷.

The only confirmed Rhenium minerals are molybdenite and copper Rhenium sulfide minerals, but it often occurs in trace amounts in molybdenum, copper, lead, zinc, platinum, niobium, and other minerals. Economically valuable Rhenium-bearing minerals are molybdenite. Generally, the Rhenium content in molybdenite concentrates ranges from 0.001% to 0.031%. However, molybdenum concentrate selected from porphyry copper ores can contain up to 0.16% Rhenium⁸.

The primary raw material for Rhenium production is a by-product of molybdenum smelting. Rhenium can also be recovered from the smelting dust and slag of some copper ores, platinum group ores, niobium ores, and even sphalerite, as well as from the waste liquid when treating low-grade molybdenum ores⁸.

Footnotes

1. Greenwood, N. N., & Earnshaw, A. (1997). Chemistry of the elements (2nd ed.). Butterworth-Heinemann.
2. Introduction of Rhenium
3. Weeks, M. E., & Leicester, H. M. (1968). Discovery of the elements. Journal of Chemical Education.
4. Emsley, J. (2001). Nature's building blocks: an A-Z guide to the elements. Oxford University Press.
5. Karol, P. J., Nakahara, H., Petley, B. W., & Vogt, E. (2003). Nomenclature of the elements: past, present, and future. Pure and applied chemistry, 75(6), 863-867.
6. Polyak, D. E. (2017). Rhenium. In Critical Minerals of the United States. U.S. Geological Survey.
7. U.S. Geological Survey, Mineral Commodity Summaries (2023).
8. Yannopoulos, S. N., & Zavras, A. (2002). Rhenium: Its geology, mineralogy, and recovery. Canadian Metallurgical Quarterly, 41(1), 7-19.