Urban mining by flash Joule heating

Abstract

Precious metal recovery from electronic waste, termed urban mining, is important for a circular economy. Present methods for urban mining, mainly smelting and leaching, suffer from lengthy purification processes and negative environmental impacts. Here, a solvent-free and sustainable process by flash Joule heating is disclosed to recover precious metals and remove hazardous heavy metals in electronic waste within one second. The sample temperature ramps to ~3400 K in milliseconds by the ultrafast electrical thermal process. Such a high temperature enables the evaporative separation of precious metals from the supporting matrices, with the recovery yields >80% for Rh, Pd, Ag, and >60% for Au. The heavy metals in electronic waste, some of which are highly toxic including Cr, As, Cd, Hg, and Pb, are also removed, leaving a final waste with minimal metal content, acceptable even for agriculture soil levels. Urban mining by flash Joule heating would be 80× to 500× less energy consumptive than using traditional smelting furnaces for metal-component recovery and more environmentally friendly.

Simultaneous Separation and Recovery of Gold and Copper from Electronic Waste Enabled by an Asymmetric Electrochemical System

“…Note that e-waste is rich in base metals (Cu, Fe, Ni, and Zn) and many high-value precious metals (Ag, Au, Pt, and Pd). 3 In particular, the percentage of copper in PCBs accounts for 20 wt %, while the gold content in waste mobile phones is up to 1200 g/t, far higher than those in the natural copper and gold minerals. 4 Taking into consideration the overwhelming economic benefit of metals recovery, ever-increasing market demand, substantial consumption, and limited supplies of metal resources, it is of paramount importance to effectively retrieve valuable metals from obsolete electronic devices in order to meet the demand for a sustainable supply of metal resources and reduce environmental impacts as well as cater to the circular economy philosophy.…”

“…If being not disposed scientifically or recovered effectively, this e-waste will cause huge environmental burdens and jeopardize human health. Note that e-waste is rich in base metals (Cu, Fe, Ni, and Zn) and many high-value precious metals (Ag, Au, Pt, and Pd) . In particular, the percentage of copper in PCBs accounts for 20 wt %, while the gold content in waste mobile phones is up to 1200 g/t, far higher than those in the natural copper and gold minerals .…”

Recycle and Reuse of Continuous Carbon Fibers from Thermoset Composites Using Joule Heating

“…[33] In another study, Joule heating was used to recover precious metals from electronic waste. [34] In this study, we explore a methodology for out-of-oven thermal recycling of carbon fibers from scrap composites (Figure 1). A DC voltage is applied across a CFRC using a DC power source; the conductive fibers enable a current to pass through it, heating up in the process.…”

In Situ Electrothermal Approach for the Synthesis of High-Performance Carbon Fiber

“…In addition, electric fields are widely used to control the microstructures of materials consisting of independent units. These features show the potential of employing electric fields to tune the orientation and graphitization of CFs. − Herein, we used an in situ electrothermal approach for the carbonization and graphitization of CFs. We initially conducted graphitization experiments using commercial CFs (T800, usually obtained via carbonization at 1400–1500 °C).…”