‘…This will curtail the need to go all over the world to mine ores in remote and dangerous places, stripping the Earth’s surface. The treasure is in our dumpsters,’
Researchers from Rice University, Texas, US, have developed a method for extracting metals from electronic waste, producing a by-product clean enough for use on agricultural land. In addition the process is said to use up to 500 times less energy than current lab methods.
The process, which has been reported in Nature Communications, uses the flash Joule heating method, where the waste is instantly heated to 5660 degrees Fahrenheit using a jolt of electricity. The precious metals are vaporized, and the gases are vented away, under vacuum, to a cold trap where they condensed to their constituent metals.
The work has been carried out in the laboratory of James M Tour, TT & WF Chao Chair in Chemistry as well as Professor of computer science, material science and nanoengineering at Rice University. Commenting, Professor Tour said that with more than 40 million tonnes of e-waste produced worldwide each year, there is plenty of potential for “urban mining.” ‘Here, the largest growing source of waste becomes treasure. This will curtail the need to go all over the world to mine ores in remote and dangerous places, stripping the Earth’s surface. The treasure is in our dumpsters,’ Professor Tour said.
The researchers noted that just one flash Joule reaction reduced the concentration of lead in the remaining char to less than 0.05 part per million, the level deemed safe for agricultural soils. Levels of arsenic, mercury and chromium were all further reduced by increasing the number of flashes.
The scalable process is said to consume some 939 kilowatt-hours per tonne of material processed, 80 time less energy than commercial smelting furnaces and 500 times less than laboratory tube furnaces. It also eliminates the lengthy purification required by smelting and leaching processes.