A consortium of organisations based in Scotland have developed a system that can separate gold, silver and palladium from old circuitry using a clever mix of biological and chemical techniques.
Better yet, the solution used to recover the metals is benign and can be safely disposed of. Now, it’s hoped the technique can be scaled up so waste metal from old TVs, laptops and mobile phones can be easily recovered and reused.
The partners include Aberdeen-based environmental tech company, SEM; WEEE Scotland, the waste services provider; the University of Edinburgh; and the Industrial Biotechnology Innovation Centre (IBioIC).
Leigh Cassidy, lead scientist at SEM, said: “There are a number of methods for removing valuable metals from electronic waste, but they are largely chemical and physical and come with an environmental cost. This project has proven the use of an approach that is more rooted in biology and, with that, is much more sustainable – each stage of the filtration process has a lower impact than any traditional manner.
"We are now looking to build the system into WEEE’s operations and then take it to other sites where processes can be made more environmentally friendly. The next stage will be commercialising the technology to full effect, and we are pulling together funding bids to make that happen."
Dr Jason Love, of the University of Edinburgh, said the approach is a step-change from existing tech, offering far greater environmental advantages.
"Many of the existing processes use smelting. That can work well, but to do that you use a lot of energy – mainly from fossil fuels – so there’s a carbon impact.
"With this project, we use hydrometallurgical methods, which massively reduce energy costs and are readily scalable. This works if you want to do it on a large or small scale."
Other methods use solvents that are difficult to recycle to dissolve valuable metals from electronic circuit boards. This generates large volumes of acidic liquid waste containing traces metals, which can be damaging to the environment.
The new method developed by the group uses recyclable solvents to extract valuable gold and copper from printed circuit boards. Other metals – such as aluminium, tin, and zinc – can then be recovered separately from the effluent using SEM’s 'Dram' filtration system, making the discharge from the extraction process environmentally benign.
Dram is manufactured using co-products from the distillation of malt whisky. The filter captures metals that can be recovered in the form of metallic nanoparticles by microbes and then purified for re-use. The final effluent from the process is also suitable to be discharged into the environment.
According to the UN’s Global E-waste Monitor 2020 report, in 2019 the UK produced the second highest level of electrical waste per capita at 23.9kg – a total 1.6 million tonnes of waste electronics. Most of this waste is transported to Asia for processing, which also contributes to the environmental impact of electronic waste.
Once commercialised, the new filtration process could not only reduce the reliance on mining new metal resources for electronics, but also open up new opportunities to drive more circular practices and create value from e-waste.