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										<p>Rare-earth elements are difficult to source and recycle, but a flash of insight led Rice University scientists to find a possible solution. </p><p>Chemist James Tour's Rice Lab reports that it has successfully extracted valuable rare-earth elements (REEs) from waste with yields high enough to solve manufacturers' problems and increase their profits. </p><p>The lab's flash Joule heating process, introduced several years ago to produce graphene from any solid carbon source, has now been applied to three sources of rare-earth elements (coal fly ash, bauxite residue, and electronic waste). to recover rare earth metals, which have critical magnetic and electronic properties for modern electronics and green technologies.</p><p>The researchers say their process is kinder to the environment by using far less energy and turning the stream of acid often used to recover items into a trickle.</p><p>The study appears in Science Advances. </p><p>Rare earth elements are not actually rare.  One of them, cerium, is more abundant than copper, and all of them are more abundant than gold.  But these 15 lanthanide elements, along with yttrium and scandium, are widely distributed and difficult to extract from mined materials.</p><p>"The United States used to mine rare-earth elements, but you also get a lot of radioactive elements," Tour said.  “You are not allowed to re-inject the water and you have to dispose of it, which is expensive and troublesome.  The day the US phased out all rare earth mining, foreign sources increased its price tenfold.”</p><p>So there's a lot of incentive to recycle what's already been mined, he said.  Much of that accumulates or is buried in fly ash, the byproduct of coal-fired power plants.  “We have mountains of it,” he said.  "The residue from burning coal is oxides of silicon, aluminium, iron and calcium that form glass around the trace elements, making them very difficult to extract."  Bauxite residue, sometimes called red mud, is the toxic byproduct of aluminum production, while e-waste comes from outdated devices like computers and smartphones. </p><p>While industrial extraction of this waste commonly involves strong acid leaching, a time-consuming, ungreen process, Rice's lab heats fly ash and other materials (combined with carbon black to improve conductivity) to about 3,000 degrees. Celsius (5432 degrees Fahrenheit).  ) in a second.  The process converts the waste into highly soluble "activated REE species."</p><p>Tour said treating the fly ash with Joule flash heating "breaks down the glass that coats these elements and converts the REE phosphates into metal oxides that dissolve much more easily."  Industrial processes use a 15 molar concentration of nitric acid to extract the materials;  the rice process uses a much milder concentration of 0.1 molar hydrochloric acid that still produces more product.</p><p>In experiments led by postdoctoral researcher and lead author Bing Deng, the researchers found that Joule-fast heating coal fly ash (CFA) more than doubled the yield of most rare-earth elements using a very mild acid compared to leaching raw CFA in strong acids.</p><p>"The strategy is general for various wastes," said Bing.  "We proved that REE recovery yields were improved from coal fly ash, bauxite residue, and e-waste using the same activation process." </p><p>The generality of the process makes it especially promising, Bing said, since millions of tons of bauxite residue and e-waste are also produced each year.</p><p>“The Department of Energy has determined that this is a critical need that must be addressed,” Tour said.  “Our process tells the country that we are no longer dependent on environmentally harmful mining or foreign sources of rare earth elements.”</p><p>Tour's lab introduced instantaneous Joule heating in 2020 to convert coal, petroleum coke and garbage into graphene, the single-atom-thick form of carbon, a process that is now commercialized.  Since then, the lab has adapted the process to turn plastic waste into graphene and extract precious metals from electronic waste.</p> 									</div>
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