By Benjamin Dekker. Image used is Electronic waste at Agbogbloshie Ghana by Muntaka Chasant, used under CC BY-SA 4.0.
Can green chemistry drastically reduce our mining and landfilling needs? Chemists at the University of Auckland are pioneering new methods for dealing with electronic waste.
When people throw away old smart phones, they are simultaneously rubbishing extraordinary wealth. E-waste from our devices contains up to 75 elements of the periodic table, derived from more than 200 different mineral commodities. The vast cast of important resources locked up in our modern hand-held electronics include copper, gold, palladium, cobalt, nickel, zinc, and rare earth metals—all indispensable for our modern lifestyles. Our everyday devices currently require worldwide extraction and refinement processes for these critical metals. Consequently, these complex and economically dense commodities are also among the biggest products of and contributors to resource-based conflicts, pollution, habitat destruction, human rights violations, and exploitative labour practices worldwide.
This destruction tied to our smart phones could be reduced if we could recycle these materials, cutting down on mining, transport, and conflict resource dependency. Finding ways to remove metals from modern devices is crucial for this. Current commercial techniques tend to use either smelting – raising waste to high temperatures and harvesting molten metal – or biotechnology – the use of special bacteria to absorb metals. These methods work well to some extent, but many valuable or hazardous metals are left behind, diminishing the problem but not eliminating it.
Ngā Ara Whetū affiliated researchers at the University of Auckland’s Centre for Green Chemical Science are working towards innovative new solutions. One method selectively extracts a wide range of metals using solvents. E-waste is ground up and dissolved in water, making a sludge. These solvents repel water and interact strongly with a range of metals that cannot be easily absorbed using other techniques. As such, the key metals are drawn out of the liquified e-waste. Director of the Centre for Green Chemical Science, Associate Professor Cameron Weber, remarked:
“[These solvents] are capable of hanging onto the metal and separating the metal out, but without actually dissolving in the water themselves. Because obviously what you don’t want to have happen is to throw something in to pull the metal out, and have it stick around in the water afterwards.”
In theory, this technique can extract metals simply from the ways that the solvent interacts with different elements of the e-waste slurry. Moreover, these solvents could be modified to selectively interact with different metals. Research on this technique is still on-going. The economic question is key: How can we minimise the quantity of solvent and maximise the metal it can extract? Further, can this process be sufficient scaled for recycling the immense quantities of e-waste that we currently produce?
William Sheard is a PhD student being supervised by Associate Professor Erin Leitao (another lead at the Green Chemical Science Centre) and received a Ngā Ara Whetū scholarship in 2023. He is tackling similar research with polysulfide ‘sponges,’ taking advantage of sulphur’s strong reactivity with metals like gold and mercury. By channelling water saturated with tiny metal particles through a special filter (with sulphur as an active agent), the solution’s motion continuously draws out the metals for reclamation. The active flow of Sheard’s proposed system is another promising step towards scaling e-waste recycling for feasible commercial use.
One key advantage of this procedure lies in the fact that sulphur itself is a common waste material – both means and method extending the working lifespan of elements. Concurrent with these studies, industry and societies can reduce the environmental destruction and human rights violations by collectively reducing consumption, extraction, and by extending product lifespans. Improving the logistics of collecting and distinguishing e-waste is also critically important.
Nonetheless, this work is a significant step forward for how we treat natural resources: “Hopefully we can displace some of the need for large-scale mining operations. While we will never be able to recover and recycle 100% of all resources, the closer we get to this will help reduce our dependence on directly extracting resources from the ground” explained Weber.
Economic and environmental sustainability can coincide through circular economies, which means keeping material in circulation through many different uses and processes for as long as possible. Using products or materials once, then disposing them is wreaking havoc all over the world. Instead, those materials and products can contribute to many additional goods if they are reused and recirculated.
By multiplying the use of valuable substances across products throughout those material’s working lifespan, we can drastically reduce our detrimental impacts on the planet and optimise our use of resources in real terms.
Further Reading:
Ngā Ara Whetū. (Jul 19, 2023). Unearthing the wealth within e-waste: Ngā Ara Whetū scholarship recipient’s research. https://www.ngaarawhetu.org/unearthing-the-wealth-within-e-waste-nga-ara-whetu-scholarship-recipients-research/.
van Osch, D. J. G. P., Parmentier, D., Dietz, C. H. J. T., van den Bruinhorst, A., Tuinier, R., & Kroon, M. C. (2016). Removal of alkali and transition metal ions from water with hydrophobic deep eutectic solvents. Chemical Communications (Cambridge, England), 52(8), 11987–1199. https://doi.org/10.1039/c6cc06105b.
