The Golden Age of E-Waste Recycling

Gold has long been utilized in electronics due to its exceptional conductivity and resistance to corrosion, making it an ideal material for a number of components within electronic devices. One of the primary reasons for its use is its ability to efficiently transmit electrical signals without degradation over time. This makes gold particularly valuable for connectors, switches, and other critical components where reliability is crucial. Additionally, its malleability allows for precise shaping and bonding, which makes gold easy to incorporate into manufacturing processes.

Due to its high cost compared to other metals, the amount of gold used in electronic devices is typically quite small. However, given the sheer volume of electronic devices produced globally, even trace amounts of gold per device add up to significant quantities overall.

The proliferation of electronic devices has contributed to a major increase in the volume of e-waste generated worldwide. As consumers upgrade their gadgets to keep pace with technological advancements, older devices quickly become obsolete and are often discarded. This has resulted in large volumes of e-waste containing valuable materials such as gold, which could potentially be recovered and reused through recycling processes.

However, harvesting gold from electronic waste presents numerous challenges. Current techniques for extracting gold from e-waste are often inefficient and costly, requiring complex processes such as chemical leaching or burning, which can also have detrimental environmental impacts. But the future of gold harvesting looks brighter, thanks to the recent work of a team at ETH Zurich. They have developed an efficient and economically viable means to recover gold from e-waste.

The researchers' solution makes use of a special type of sponge that can soak the metal up. The sponges are made from proteins in whey, an abundant dairy byproduct. After being extracted, the proteins are denatured under acidic conditions and high temperatures, then are aggregated into a gel. Once dried, the sponge made of protein fibrils is ready to harvest gold.

To use the sponges, the team dissolved printed circuit boards, and the components mounted on them, in a bath of acid. This treatment ionizes the gold. When a sponge is placed into this solution containing gold ions, the gold is drawn to the protein fibers, where they adhere securely. As a final step, the sponge is removed from the solution and heated, which causes the gold to turn into flakes, which can be removed.

Using this method, twenty old computer motherboards were treated. This produced a 450 milligram chunk of 22 carat gold. While the sponge does not exclusively attract gold, it attracts gold with more efficiency than other metals — the harvested material was 91% gold and 9% copper. This may not amount to very much money, but considering the volume of e-waste that exists, there is plenty of room for profit — especially when factoring in that the cost of this entire harvesting process is 50 times less than the value of the gold that can be retrieved.

This technology not only offers individuals the possibility of making money, but it also incentivizes e-waste recycling, making it a win-win situation. The researchers are still working to ready their technology for the market, so it may be a while before it can be applied in real-world situations. When it is ready, they suggest that their methods could be useful beyond harvesting from e-waste — industrial waste from microchip manufacturing and gold-​plating processes might also be good sources.