Textiles help selectively recover gold from e-waste

Plain weave. (Reference image by Dee.lite, Wikimedia Commons.)

Researchers at the Korea Institute of Science and Technology (KIST) have developed a solution that uses textile materials to selectively recover high-purity gold from electrical and electronic waste containing various metals.

In a paper published in the Chemical Engineering Journal, the researchers explain that adsorbents for metal recovery are generally granular in shape to increase adsorption efficiency based on high specific surface area but are difficult to control underwater, resulting in low recovery rates and even secondary environmental pollution.

On the other hand, fibre-like materials are easy to control underwater and can be made into various shapes through the weaving process, so they have high potential for industrial application. However, due to their thin thickness and low strength, they are easily broken when gold recovery is applied to the support.

The KIST researchers, thus, have chemically immobilized alkaline molecules on the surface of polyacrylonitrile (PANF) fibres to improve both molecular gold recovery performance and structural stability. The amine-containing polymer fibre has a dramatically larger surface area, which can improve the adsorption performance of gold ions (Au) in waste by up to 2.5 times (from 576 mg/g to 1,462 mg/g) compared to the team’s previously developed granular gold adsorption material.

The developed fibrous adsorbent showed a gold recovery efficiency of more than 99.9% in solutions obtained by leaching real CPUs and achieved a gold recovery efficiency close to 100% in a wide range of pH 1-4, which includes most waste liquids.

The researchers considered it noteworthy that only gold ions can be recovered with a high purity of over 99.9%, even in the presence of 14 other metal ions coexisting in the solution. Furthermore, the gold recovery rate was maintained at 91% even after 10 uses.

“By enabling efficient and eco-friendly metal resource recovery, the fibre-type adsorbent developed by KIST can reduce Korea’s dependence on resource imports and prepare for the risk of rising raw material prices,” Jae-Woo Choi, senior author of the study, said in a media statement. “We plan to expand the scope of future research to selectively recover various target metals in addition to gold.”

For context, Choi explained that Korea relies on imports for most of its metal resources and in recent years, due to resource depletion and rising raw material prices, recycling plans have emerged.

Companies like SK Hynix have established plans to increase the percentage of copper, gold, and other metals recovered and reused from waste generated in the semiconductor manufacturing process to more than 30% by 2030. Samsung Electronics, on the other hand, is running a collection program for used mobile phones in cooperation with E-circulation Governance, a non-profit corporation.

The researcher also noted that the global circular economy market is expected to more than double in size from approximately $338 billion in 2022 to $712 billion in 2026.