Fig. 1: Recovery of precious metals by flash Joule heating (FJH).

a Schematic of the FJH and evaporative separation system. The system was composed of three parts, including FJH for metal evaporation, the vacuum system for mass transport, and the cold trap for volatiles condensation. b Picture of a printed circuit board (PCB). Scale bar, 5 cm. Inset, the mixture of carbon black (CB) with PCB powder. Scale bar, 2 cm. c Concentrations of precious metals in PCB as determined by inductively coupled plasma mass spectrometry (ICP-MS). d Currents vs time recorded under different FJH voltages. e Real-time temperature measurements at different FJH voltages by fitting blackbody radiation emitted from the sample. f Vapor pressure–temperature relationship of precious metals and carbon. g Recovery yield of precious metals by condensing the evaporated gas components. The recovery yield is the average of three independent FJH experiments (n = 3).