Abstract: Advanced electronics increasingly rely on rare earth or specialty elements (RESE), and less than 40% of electronics and 1% of critical metals are recycled in the U.S. Further, the increasing complexity of high-performance electronics exacerbates the difficulty of relying on recycled feedstocks to sustain the material supply chain. Related to this, methods to capture RESE during the manufacturing process could increase the atom economy in the fabrication process and ultimately reduce the reliance on virgin and foreign RESE sources. Here, we propose a three-fold approach to surmount these challenges: (1) employ carbon nanotube-enabled filters to electrochemically precipitate metals of interest out of industrial waste streams, (2) integrate these filters in a multi-stage system that can precipitate multiple metals in series and selectively from a mixed metal stream, and (3) subsequently release relatively pure metals from each filter stage to enable reuse. Optimization parameters for single metal streams include pH, flow rate, and applied voltage, where pH and applied voltage have the greatest influence on metal recovery. In addition, chelating agents and redox mediators will be used to optimize recovery and selectivity. Preliminary data show high recovery (40-96%) of neodymium, europium, scandium and copper from single metal streams, with successful recovery and separation of copper and europium from a mixed metal stream, yielding 96 ± 2% recovery of copper and 65 ± 12% recovery of europium. Finally, to assess the environmental impact of the technology itself during the use phase of the life cycle, we evaluated the release of carbon nanotubes and other plasticizer chemicals to the effluent stream, seeking to minimize the release of these materials as part of the design objectives. Overall, the technique shows promise for surmounting limitations in RESE supply chain sustainability and aids environmental protection by limiting the release of materials from electronics processing and other large-volume waste streams.

Electrochemical deposition for the recovery and separation of metals: A novel approach for reclaiming rare earth and specialty elements from industrial waste and processing streams

253rd National Meeting (2017)

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