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A team of chemists in Canada has developed a way to process metals without using toxic solvents and reagents. 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.

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鈥淎t a time when natural deposits of metals are on the 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,鈥� says Jean-Philip Lumb, an associate professor in 黑料不打烊 University鈥檚 Department of Chemistry. 鈥淭hat鈥檚 what makes our advance so important.

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The discovery stems from a collaboration between Lumb and Tomislav 贵谤颈拧膷颈膰 at 黑料不打烊 in Montreal, and Kim Baines of Western University in London, Ont. 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.

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The research could mark an important milestone for the 鈥済reen chemistry鈥� movement, which seeks to replace toxic reagents used in conventional industrial manufacturing with more environmentally friendly alternatives. Most advances in this area have involved organic chemistry 鈥� the synthesis of carbon-based compounds used in pharmaceuticals and plastics, for example.

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鈥淎pplications of green chemistry lag far behind in the area of metals,鈥� Lumb says. 鈥淵et metals are just as important for sustainability as any organic compound. For example, electronic devices require numerous metals to function.鈥�

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There is no single ore rich in germanium, so it is generally obtained from mining operations as a minor component in a mixture with many other materials. Through a series of processes, that blend of matter can be reduced to germanium and zinc.

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鈥淐urrently, in order to isolate germanium from zinc, it鈥檚 a pretty nasty process,鈥� Baines explains. The new approach developed by the 黑料不打烊 and Western chemists 鈥渆nables you to get germanium from zinc, without those nasty processes.鈥�

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To accomplish this, the researchers took a page from biology. Lumb鈥檚 lab for years has conducted research into the chemistry of melanin, the molecule in human tissue that gives skin and hair their color. Melanin also has the ability to bind to metals. 鈥淲e asked the question: 鈥楬ere鈥檚 this biomaterial with exquisite function, would it be possible to use it as a blueprint for new, more efficient technologies?鈥欌��

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The scientists teamed up to synthesize a molecule that mimics some of the qualities of melanin. In particular, this 鈥渙rganic co-factor鈥� acts as a mediator that helps to extract germanium at room temperature, without using solvents.

The system also taps into 贵谤颈拧膷颈膰鈥檚 expertise in mechanochemistry, an emerging branch of chemistry that relies on mechanical force 鈥� rather than solvents and heat 鈥� to promote chemical reactions. Milling jars containing stainless-steel balls are shaken at high speeds to help purify the metal.

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"This shows how collaborations naturally can lead to sustainability-oriented innovation,鈥� 贵谤颈拧膷颈膰 says. 鈥淐ombining 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"

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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.

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鈥淭here鈥檚 a tremendous amount of work that needs to be done to get from where we are now to where we need to go,鈥� Lumb says. 鈥淏ut the platform works on many different kinds of metals 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.鈥�

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Funding for the research was provided by the Natural Sciences and听Engineering Research Council of Canada, the National Natural Science Foundation of China, the Soochow University-Western University Center for Synchrotron Radiation Research, and the Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University.

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鈥淎 chlorine-free protocol for processing germanium,鈥� Martin Glavinovi膰 et al., Science Advances, 5 May 2017. DOI: 10.1126/sciadv.1700149

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IMAGE: Strategy for reducing the environmental impact of a refining process: replace hazardous chemicals with more benign and recyclable compounds. CREDIT: Michael J. Krause (Western University)

VIDEO: Using solvent-free mechanochemical techniques, milling jars containing stainless-steel balls are shaken at high speeds to promote chemical reactions. CREDIT: 听Michael Brand (University of Cardiff) and Jean-Louis Do (黑料不打烊 University)

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