PNNL Researchers Seek Value from Discarded Electronics

When fulfilled holiday wish lists include a new smartphone, upgraded laptop or the latest game console, their retired predecessors might be in cluttered junk drawers or landfills by January. Thanks to a new method developed by scientists at the Department of Energy’s Pacific Northwest National Laboratory, it may be possible to recover the critical minerals in these discarded electronics. 

Their efforts can help address one of the world’s fastest growing waste streams, known as “e-waste,” while also reducing the costs, environmental impacts and geopolitical tension associated with mining, processing or purchasing these minerals. 

Materials scientists are exploring how to “mine” electronic waste for critical minerals such as dysprosium, neodymium and manganese. These materials serve various purposes in today’s electronics, from enhancing the magnetic properties of hard drives to making speakers sound better and improving the performance of rechargeable batteries. 

Recycling the valuable materials found in discarded electronics is not a new idea. However, conventional methods are not cost-effective because they are slow, energy-intensive and require hazardous specialty chemicals. PNNL researchers developed faster and more environmentally friendly separation techniques based on their fundamental understanding of material transport and reactivity. 

In one effort focused on neodymium and dysprosium, both commonly used in magnets, researchers built a device that funnels two liquid streams into a reaction chamber. The first contains the dissolved e-waste with both minerals. The other is a chemical solution that separates the minerals, extracting the neodymium and dysprosium solids as the two liquids merge.

Knowing that subtle differences in the transport and reactivity of these minerals would influence how quickly they diffuse and form solids, researchers successfully separated and purified solid forms of neodymium and dysprosium despite their similar properties. Their process took just hours, while typical separation processes take as long as seven days.

The key differences are the way the materials are mixed and that the PNNL-developed system does not need to reach equilibrium for separation to occur. That means the scientists’ new system begins working immediately instead of waiting for the temperature, pressure and other properties to stabilize. 

The new device not only isolated and separated minerals faster than conventional methods but also achieved higher purity—and it can be scaled up easily. As a next step, the developers are modifying the devices to efficiently extract larger amounts of the minerals.

In a related effort, researchers performed proof-of-concept experiments to show a gel-based system could be used to recover nearly pure manganese from a solution that mimics dissolved lithium-ion battery waste. 

Advancing this technology could realize significant economic and environmental benefits considering lithium-ion batteries are in everything from children’s toys to luxury cars. It is estimated that only about 5% of the world’s lithium-ion batteries are recycled due to the expense and technical challenges associated with doing so. 

The manganese extraction technique involves placing the dissolved minerals from batteries in a specially treated gel. The metals in the solution were separated and extracted as they encountered the gel, based on their individual transport and reactivity rates. 

While the scientists showed it was possible to extract battery-grade manganese from a battery waste simulant, the same approach potentially could be used to extract other minerals such as lithium, cobalt and nickel from a spent-battery waste stream.

In both the liquid and gel separation methods, the researchers at PNNL took a back-to-the-basics approach to technology development. I am hopeful that their innovative techniques and streamlined solutions will make it easier and cheaper to recycle our e-waste and recover valuable materials that can be used in our next-generation electronic gadgets.

Steven Ashby, director of Pacific Northwest National Laboratory, writes this column monthly. To read previous Director's Columns, please visit our Director's Column Archive.