Lightweight lithium metal is a heavy-hitting critical mineral, serving as the key ingredient in the rechargeable batteries that power phones, laptops, electric vehicles and more. As ubiquitous as lithium is in modern technology, extracting the metal is complex and expensive. A new method, developed by researchers at Penn State and recently granted patent rights, enables high-efficiency lithium extraction - in minutes, not hours - using low temperatures and simple water-based leaching.
"Lithium powers the technologies that define our modern lives - from smartphones to electric vehicles - and has applications in grid energy storage, ceramics, glass, lubricants, and even medical and nuclear technologies," said Mohammad Rezaee, the Centennial Career Development Professor in Mining Engineering at Penn State, who led the team that published their approach in Chemical Engineering Journal. "But its extraction must also be environmentally responsible. Our research shows that we can extract lithium, and other critical minerals, more efficiently while drastically reducing energy use, greenhouse gas emissions and waste that's difficult to manage or dispose of."
Australia, Chile and China lead the world in lithium supplies, exporting to countries competing in increasingly advanced technologies that depend on the mineral. Chile and Argentina are responsible for 97% of lithium exports to the United States, which imports more than twice what it can extract from domestic resources despite housing millions of metric tons of lithium deposits. The issue is the time, financial cost and environmental impact of extracting lithium from the rocks where it naturally occurs, according to Rezaee.
Rezaee and his research group members, Chandima Hevapathiranage and Shihua Han, who are pursuing doctoral degrees in energy and mineral engineering, with the mining and mineral process engineering option, at Penn State, have a solution, though. With far less energy consumption and fewer harsh chemicals than traditional methods, their acid-free approach can extract more than 99% of a rock's available lithium in minutes, compared to the hours of conventional extraction that produces roughly 96% of the available lithium.
"What makes this approach especially promising is its compatibility with existing industrial infrastructure," Rezaee said, explaining that the new process is designed with scalability and practicality in mind, and it does not require extreme heat or the use of acids. "It uses common materials like sodium hydroxide - a common compound used in making soap and found in many household cleaners - and water, and it operates at much lower temperatures than traditional techniques. That makes it not just cleaner and faster, but easier to implement at scale."
Conventional lithium extraction involves either coaxing rock ores into giving up the metal or evaporating ponds of lithium-rich brine. Evaporation requires significant amounts of water and takes too long to match industry demands. Directly extracting lithium from mined rocks is quicker than brine evaporation but involves heating the minerals to incredibly high temperatures of 1,110 degrees Celsius - 2,300 degrees Fahrenheit - and maintaining the temperature for two hours. This makes the lithium mineral porous and prepares the lithium to separate from the rock. In the next step, the porous mineral is treated with sulfuric acid and heated to 482 degrees Fahrenheit for two hours. Known as sulfuric acid baking, this step eventually dissolves much of the lithium. The resulting acidic lithium solution is then treated to neutralize the acid and purify the metal.
"Each step of the conventional method, especially the high-temperature treatment, emits a substantial amount of carbon dioxide," Rezaee said, explaining that the sulfuric acid also poses environmental concerns and leaves hazardous byproducts. "The process requires significant equipment investment and has challenges for temperature control and energy recovery. Impurities lead to lithium loss, and the acidic lithium solution requires significant chemical consumption to become basic for final extraction."
When Rezaee and his team first considered improving this process, they realized they could eliminate the need for phase transformation - the extreme heating and sulfuric acid baking that loosens lithium ions from the mineral.
"We used thermodynamic modeling to understand how the lithium-bearing minerals might interact with different chemical agents, and then validated those predictions through laboratory experiments," Rezaee said. "We found that mixing the lithium-containing mineral, called spodumene, with sodium hydroxide, at relatively low temperatures converts the mineral into lithium-bearing water-soluble phases."
They also investigated the use of microwave heating for this low temperature reaction - similar to heating food in a microwave rather than an oven - to cut the processing time to just minutes.
This reaction produces lithium sodium silicate, a compound that dissolves readily in room-temperature water. When water is added, the lithium leaches out in about a minute. Because the resulting solution is already basic, meaning non-acidic, it also eliminates the need for the chemical additions that conventional lithium extraction requires to shift from acidic to basic. The researchers can immediately add a compound that solidifies the lithium so that it can be easily collected.
According to Rezaee, the process can also work to extract lithium and two other critical minerals - rubidium and cesium, which are used in electronics, quantum computing, solar panels, atomic clocks, satellite navigation systems, batteries and even as a rocket propellant - from lepidolite, another rock ore. It can also extract lithium from clay sources. The team is now working toward scaling up their approach and refining the process for industrial application.
The Penn State College of Earth and Mineral Sciences supported this work through the George H. Deike, Jr. Research Award.
