McGill is at it again. Just months after researchers at the Canadian university revealed that metal powders could provide a zero-carbon, closed-loop alternative to traditional fossil fuels, a team of chemists have uncovered a way to produce and refine metals without the aid of toxic solvents or reagents.
According to Jean-Philip Lumb, an associate professor in McGill’s Department of Chemistry, the discovery could prove to be invaluable as natural deposits of metal continue to decline. “There is a great deal of interest in improving the efficiency of metal refinement and recycling, but few disruptive technologies are being put forth,” said Lumb. “That’s what makes our advance so important.”
Lumb said applications of green chemistry in metals “lag far behind” other areas. “Yet metals are just as important for sustainability as any organic compound.”
There is no single ore rich in germanium and so it is generally obtained from mining operations as a minor component in a mixture with other materials. Through a series of processes, that blend of matter can be reduced to germanium and zinc.
Conventional processing techniques to purify metals typically rely on the application of chlorine and hydrochloric acid. McGill’s process, which was developed in collaboration with Western University and highlighted in a recent article on Science Advances, however, uses organic molecules. The widespread use of the new technology could help usher industrial manufacturing towards a more sustainable model by eliminating toxic solvents and reagents.
To develop the technology, Lump’s lab drew inspiration from melanin, which, in addition to giving skin and hair their color, has the ability to bind to metals. “We asked the question: ‘Here’s this biomaterial with exquisite function, would it be possible to use it as a blueprint for new, more efficient technologies?’” said Lumb.
Researchers synthesized a molecule that mimics the organic co-factor qualities of melanin, and were able to extract germanium at room temperature without the use of solvents. Elements of mechanochemistry, chemistry that deals with the conversion of chemical energy into mechanical work, are also present in the system, with milling jars containing stainless-steel balls being shaken at high speeds to purify the metal.
“This shows how collaboration naturally can lead to sustainability oriented innovation,” said Tomislav Friscic, an associate chemistry professor at McGill and an expert in mechanochemistry. “Combining elegant new chemistry with solvent-free mechanochemical techniques led us to a process that is cleaner by virtue of circumventing chlorine-based processing, but also eliminates the generation of toxic solvent waste.”
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.
“There is a tremendous amount of work that needs to be done to get from where we are now to where we need to go,” said Lumb. “But the platform works on many different kinds of metal and metal oxides and we think that it could become a technology adopted by industry. We are looking for stakeholders with whom we can partner to move this technology forward.”