Flash separation of metals by electrothermal chlorination

Abstract

Metal recycling plays a crucial role in mitigating the shortage of critical metals and reducing reliance on primary mining. Current liquid hydrometallurgy involves substantial water and chemical consumption with troublesome secondary waste streams, while pyrometallurgy lacks selectivity and requires substantial energy input. Here we develop an electrothermal chlorination and carbochlorination process, and a specialized compact reactor, for the selective separation of individual critical metals from electronic waste. Our approach uses programmable, pulsed current input to achieve precise control over a wide temperature range (from room temperature to 2,400 °C), short reaction durations of seconds and rapid heating/cooling rates (103 °C s−1) during the process. The method capitalizes on the differences in the free energy formation of the metal chlorides. Once conversion to a specific metal chloride is achieved, that compound distills from the mixture in seconds. This allows both thermodynamic and kinetic selectivity for desired metals with minimization of impurities. Metal recycling plays a crucial role in mitigating the shortage of critical metals. Here the authors develop an electrothermal chlorination process incorporating direct electric heating into chlorination metallurgy for rapid and selective recovery of metals that are critical in electronics.