Electrochemical reactor grabs 97.5% of lithium from geothermal sources
Michael Franco

Lithium-ion batteries power everything from our vape pens to electric cars, but they have one glaring issue: they rely on lots of hard-to-harvest lithium. A new reactor from Rice University is set to make the whole process easier and safer.

It's hard to pick up any rechargeable device these days that doesn't have a lithium-ion battery inside. While there have been alternatives floated, such as those based on potassium or sodium, lithium is currently where it's at in the contemporary battery market. That's primarily because, despite occasionally bursting into flames, Li-ion batteries have an excellent energy density that lets them hold a lot of charge in a relatively small size. They are also fairly lightweight.

Lithium-ion batteries are so popular, in fact, that it's predicted their demand will grow seven-fold by 2030, largely driven by the continued adaptation of electric cars. In terms of dollars, that growth amounts to US$56.8 billion in 2023 to US$187.1 billion by 2032.

The issue with this rapidly growing demand however, is that lithium itself is a problematic element. While it is the 31st most abundant element on the planet, this fact actually makes it fairly rare. What's more, lithium is often trapped in rocks or geothermal brines where its concentration can be quite low, so extracting it is an energy-intensive process that often comes with the risk of creating hazardous gasses. Digging lithium mines can also damage natural habitats and divert water from nearby communities, as it takes about 2.2 million liters of water to create one ton of lithium.

Game changer

Enter a new electrochemical reactor from researchers at Rice University, which is being touted as a game changer for lithium harvesting.

The machine tackles one of the major issues with harvesting lithium from brines found in geothermal water sources. While such sources are good places to find lithium, the brines contain a host of other chemicals with similar ionic sizes and charges including magnesium, calcium, sodium, and potassium. Isolating only the lithium from this chemical stew is extremely challenging. What's more, the brines often contain a lot of chloride ions which can turn into extremely toxic chlorine gas during traditional electrochemical processes to isolate the lithium.

So the Rice team built a three-chambered reactor that has a newly developed lithium-ion conductive glass ceramic (LICGC) membrane in the middle. This membrane is often used inside lithium-ion batteries, but it was never before used in a reactor of this kind. The membrane proved effective at letting only the lithium ions pass through while holding back ions of the other chemicals, especially the potentially harmful chloride ions. In testing, the reactor not only dramatically limited the production of chlorine gas, but it achieved a lithium purity rate of 97.5%.

“This reactor could represent a major step forward in making lithium extraction both more efficient and less harmful to the environment,” said study co-author Sibani Biswal.

“Our field has long struggled with the inefficiencies and environmental impacts of lithium extraction,” added co-author Haotian Wang, Rice associate professor of chemical and biomolecular engineering. “This reactor is a testament to the power of combining fundamental science with engineering ingenuity to solve real-world problems.”

During testing the researchers did find a potential issue with the reactor: sodium ions built up on the LICGC membrane. Such a build-up could affect the reactor's efficiency, so one strategy they found to combat it would be to lower the sodium content of the brine before running the reaction. Another would be to conduct future research to see what other methods – such as specialized membrane coatings – might keep the sodium ions from attaching.

The study detailing the reactor's development and performance has been published in the journal Proceedings of the National Academy of Sciences.

Source: Rice University

 

Michael Franco has been writing about the serious and silly sides of science and technology for years for publications including Discovery Channel Magazine, Discover Magazine and CNET. By far his favorite home so far is at New Atlas where he's allowed all the beakers and Bunsen burners he needs in which to mix his words. The mountains of North Carolina, where he now lives with his wife and two giant poodles, offer the perfect foil to way too much screen time.

 

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