RIVM on Advanced Materials, April 2024

Electronic waste (e-waste) is a valuable source of precious and rare metals. Recycling of e-waste is an essential step towards sustainability. Scientists are currently studying methods to convert the metals present in e-waste into nanoparticles. However, it is important to consider the possible risks associated with this process to maximise its positive environmental impact.

Recycling of electronic waste

Electronics contain toxic substances, such as heavy metals like cobalt and rare elements, which are mainly sourced from China. These harmful substances may be released into the environment during the waste stage of electronics. To prevent this, it is essential to recycle electronic waste (e-waste).

Apart from the benefits of e-waste recycling, it is important to consider the safety of recycling activities. This includes concerns about workers' exposure to toxic substances during e-waste recycling. The e-waste recycling technologies themselves are also not always sustainable. They commonly emit greenhouse gases and often require a lot of energy. Melting parts of the waste for instance requires high temperatures.

Alternative means of processing e-waste

A group of Colombian researchers has reviewed options to deal with e-waste that could reduce its harmful impact. They focussed on processes that turn e-waste into metallic nanoparticles, which are in high demand for various purposes. These processes follow the principles of Green Chemistry. This means they use less energy and fewer chemicals and produce less harmful waste. The authors used waste printed circuit boards (WPCBs) as an example, as they are a significant part of e-waste.

To turn e-waste into nanoparticles, a well-organized collection system is needed first. Then, the waste is pre-processed using methods like magnetic separation, cutting, and grinding. After that, bioleaching and biosorption are used. This is then followed by sustainable green synthesis using natural resources like microorganisms, plants, plant extracts, and their waste products. Algae can also be used to produce nanoparticles.

Some studies have reported promising outcomes using green chemistry as an eco-friendly approach for nanoparticle synthesis from WPCBs. This approach uses non-toxic solvents and environmentally benign techniques. However, further exploration of innovative techniques is necessary to make it feasible for widespread industrial use. And the idea that WPCBs can be a source of nanomaterials needs promotion. The authors conclude: “Sustainable metal nanoparticle synthesis from electronic waste, particularly WPCBs, reveals promising prospects for addressing environmental challenges and advancing technology”.

Reflections by RIVM

E-waste is of increasing societal concern. It has come to light that e-waste processing is currently not being done sustainably. The lack of circularity and the unsustainable recycling processes are significant concerns. The safety of workers in the e-waste sector is also of concern, particularly in illegal e-waste recycling practices. Toxic substances being released into the environment is another primary concern.

All this points towards sustainable recycling of e-waste being crucial. Recycling precious and rare metals in e-waste into metallic nanoparticles is a potentially important innovation. Green Chemistry-based methods for synthesising metallic nanoparticles of e-waste could address many concerns. The review has identified several potential pitfalls to address before large-scale application of these green technologies is possible. The main issue to address is the development of a cascade of processes and technologies. This should start with efficient waste collection and end with the production of nanoparticles. This cascade must meet all sustainability criteria, including minimising hazards and toxic substance emissions. But it should also promote social welfare and ensure the economic sustainability of the overall process.

It is clear that there is still a long way to go before a sustainable alternative for the production of metallic nanoparticles is developed at an industrial scale. However, current developments are quite encouraging.

RIVM on Advanced Materials April 2024