Electronic waste, including PCBs, is a rapidly growing problem as consumers endlessly replace their electronic gadgets. Regulations can go so far to nudge this waste into a recycling stream, but there is still the pressing need for the technology to process the waste.
The retrieval and extraction of useful metals from electronic waste will be a critical part of creating a sustainable future if that is to be technology led. Many metals are relatively rare or found only in geopolitically sensitive regions of the world. More to the point, we have tonnes of discarded devices, circuit boards, and wiring sitting in recycling dumps and landfills. If there were a simple way to extract metals, such as copper, from these resources, that use less energy and fewer resources than mining the ores, then that would offer us a more environmentally friendly option to sourcing copper.
Jayashree Mohanty, Puspita Biswal, Subhashree Subhasmita Mishra, and Tamasa Rani Das Mohapatra of the C.V. Raman Global University in Bhubaneswar, Odisha, India, have now demonstrated an approach to extracting copper from printed circuit boards that does not require the PCBs to be dismantled. Their approach, reported in the International Journal of Environmental Engineering, uses pieces of chopped up PCBs as one electrode in an acidic solution, the electrolyte, with the other electrode is a stainless steel plate. By passing an electric current through the electrodes and the solution it is possible to dissolve the copper as positive ions into the solution. The current then drives these ions towards the negative electrode, the steel plate, where they are deposited as metallic copper. This copper plating can be readily removed from the steel electrode.
This simplified electrochemical copper extraction process avoids the usually energy-intensive mechanical shredding or chemical leaching process used in recycling and so uses less energy overall as well as minimizing processing waste and chemical pollutants. It thus has the potential to extract copper from the electrical waste stream much more effectively than was previously possible.
The team add a not-so-secret sauce to their copper extraction recipe, a salt called sodium sulfate. This substance, added to the electrolyte, buffers the solution and at a certain concentration improves the current density and efficiency increasing the amount of copper dissolved from the PCBs and deposited on to the steel cathode. The researchers found that a concentration of 0.03 molar sodium sulfate gave them the highest current efficiency, at 77%, However, the highest copper purity (99%) was obtained at 0.02 molar. There will thus be a compromise in process efficiency and retrieval rates using this additive.
Mohanty, J., Biswal, P., Mishra, S.S. and Mohapatra, T.R.D. (2025) ‘Electrochemical recovery of copper from the waste computer printed circuit board’, Int. J. Environmental Engineering, Vol. 13, No. 1, pp.1–11.