The team was led by Rice University’s James Tour, the T.T. and W.F. Chao Professor of Chemistry and professor of materials science and nanoengineering. Their findings are detailed in Nature Chemical Engineering.
“Our process offers significant reductions in operational costs and greenhouse gas emissions, making it a pivotal advancement in sustainable recycling,” Tour said in a statement.
The new technique enhances the recovery of critical metals and builds on Tour’s earlier work in waste disposal using flash Joule heating (FJH). This process involves passing an electric current through a material to rapidly heat it to extremely high temperatures, transforming it into different substances.
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The researchers applied FJH chlorination and carbochlorination processes to extract metals including gallium, indium and tantalum, from e-waste. Traditional recycling methods such as hydrometallurgy and pyrometallurgy are energy-intensive, produce harmful waste streams and involve large amounts of acid.
In contrast, the new method eliminates these challenges by enabling precise temperature control and rapid metal separation without using water, acids or other solvents.
“We are trying to adapt this method for recovery of other critical metals from waste streams,” said Bing Deng, former Rice postdoctoral student, current assistant professor at Tsinghua University and co-first author of the study.
The scientists found that their method effectively separates tantalum from capacitors, gallium from discarded light-emitting diodes and indium from used solar conductive films. By precisely controlling the reaction conditions, the team is said to have achieved a metal purity of over 95 per cent and a yield of over 85 per cent.
The method also holds promise for the extraction of lithium and rare Earth elements, said Shichen Xu, a postdoctoral researcher at Rice and co-first author of the study.
“This breakthrough addresses the pressing issue of critical metal shortages and negative environmental impacts while economically incentivising recycling industries on a global scale with a more efficient recovery process,” Xu said.
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