A team of chemists from McGill University in Montreal, Quebec, Canada, and Western University in London, Ontario, Canada, have developed a way to process metals without toxic solvents and reagents. Their innovation could help reduce negative environmental impacts of metal extraction from raw materials and electronic scrap.
As reported by McGill, “The system, which also consumes far less energy than conventional techniques, could greatly shrink the environmental impact of producing metals from raw materials or from post-consumer electronics…In an article published recently in Science Advances, the researchers outline an approach that uses organic molecules, instead of chlorine and hydrochloric acid, to help purify germanium, a metal used widely in electronic devices. Laboratory experiments by the researchers have shown that the same technique can be used with other metals, including zinc, copper, manganese and cobalt.”
The development is an interesting example of biomimicry. Germanium is a semiconductor not found in substantial quantities in any one type of ore, so a series of processes are used to reduce mined materials with small quantities of the metal to a mixture of germanium and zinc. Isolation of germanium from the zinc in this resulting mixture involves what one of the researchers called “nasty processes.” For an alternative less dependent upon toxic materials and energy use, the researchers found inspiration in melanin, the pigment molecule present in skin, hair, and irises of humans and other animals. Besides contribution to coloration, melanin can bind to metals. The researchers synthesized a molecule that mimics some of melanin’s metal-binding qualities. Using it they were able to isolate germanium from zinc at room temperature, without solvents.
As the McGill article states, “The next step in developing the technology will be to show that it can be deployed economically on industrial scales, for a range of metals.”
Read the full story, published June 7, 2017 by the McGill Newsroom at https://www.mcgill.ca/newsroom/channels/news/more-sustainable-way-refine-metals-268517.
See also “A chlorine-free protocol for processing germanium,” Martin Glavinović et al., Science Advances, 5 May 2017. DOI: 10.1126/sciadv.1700149 http://advances.sciencemag.org/content/3/5/e1700149
To learn more about germanium and its applications (including fiber-optics, infrared optics, solar electric applications, and LEDs), see the Wikipedia article on germanium at https://en.wikipedia.org/wiki/Germanium.