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A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 2 1 9 PROCESS TECHNOLOGY FLASHING E-WASTE Researchers at Rice University, Houston, developed a way to extract valuable metals from electronic waste that uses significantly less energy than current lab methods and produces a byproduct clean enough for agricultur- al land. They adapted the flash Joule heating method to produce graphene from carbon sources like plastic and food waste to recover rhodium, palladi- um, gold, and silver for reuse. The new research also demonstrates the remov- al of highly toxic heavy metals including chromium, arsenic, cadmium, mercury, and lead from the flashed materials. Instantly heating the waste to 3400 ° K—or 5660 ° F—with a jolt of elec- tricity vaporizes the precious metals, and the gasses are vented away for separation, storage, or disposal. Once flashed, the process relies on evapo- rative separation of the metal vapors. processed into hybrid glasses. The re- searchers were able to show how nor- mally nonmeltable substances from the MOF family of zeolitic imidazolate frameworks can be converted into a liq- uid state and, finally, a glass. “In this way,” they explain, “the desired com- ponent can be obtained, for example, in the form of a membrane or a disk.” The key to future applications is the interactions taking place between the ionic liquid and the MOF materi- al. These determine the reversibility of the process—the possibility of washing out the auxiliary liquid after the melting process. If the reactions are not adapt- ed, either the pore surface is not ade- quately stabilized or there is an irrevers- ible chemical bond between the MOF and parts of the ionic liquid. Therefore, ideal combinations of liquids, matrix materials, and melting conditions must be identified with a view to the desired application, so that large-volume ob- jects would become possible. www. uni-jena.de/en , www.cam.ac.uk . The flash Joule heating process has been adapted to recover valuable and toxic metals from electronic waste. Courtesy of Jeff Fitlow/Rice University. The vapors are then transported from the flash chamber under vacuum to another vessel, a cold trap, where they condense into their constituent met- als. The researchers reported that one flash Joule reaction reduced the con- centration of lead in the remaining char to below 0.05 parts per million, the level deemed safe for agricultural soils. Lev- els of arsenic, mercury, and chromium were all further reduced by increasing the number of flashes, which take only one second each. The scalable Rice process eliminates the lengthy purifi- cation required by smelting and leach- ing methods. With more than 40 million tons of e-waste produced globally every year, the researchers say there is plen- ty of potential for this “urban mining.” rice.edu . MELTING THE UNMELTABLE Due to the special properties of metal-organic framework compounds (MOFs), they are considered to have great potential for future applications in energy and environmental technolo- gy, in bio and life sciences, and as sen- sor components. The basis for the nu- merous applications is their high and largely controllable porosity. As MOFs are predominantly in powder form, a primary challenge is producing bulk components. Now, scientists from Frie- drich Schiller University, Germany, and the University of Cambridge, U.K., are looking to glasses as a solution. To produce components for indus- trial applications from MOFs, they must first be melted down before they can be BRIEF Wall Colmonoy Ltd., U.K., completed an $825,000 upgrade to its casting foundry in Wales, adding new induction melting equipment and magnetically screened furnaces. The foundry supports multiple casting methods including investment, centrifugal, sand cast, and vacuum cast processes to serve multiple industries such as food, steel, glass, aerospace, and oil and gas. wallcolmonoy.com . Vahid Nozari at the University of Jena examines the new synthetic glass. Courtesy of Jens Meyer/University of Jena.