Penn process extracts lithium quickly at low temperatures

Research lead Mohammad Rezaee, the Centennial Career Development Professor in Mining Engineering at Penn State, said that as well as batteries, lithium has applications in grid energy storage, ceramics, glass, and lubricants.

“But its extraction must also be environmentally responsible, said Rezaee. “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."

The United States imports more than twice what it can extract from domestic lithium 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, said Rezaee.

Now, with far less energy consumption and fewer harsh chemicals than traditional methods, the acid-free approach can extract over 99 per cent of a rock’s available lithium in minutes, compared to the hours of conventional extraction that produces roughly 96 per cent of the available lithium.

“What makes this approach especially promising is its compatibility with existing industrial infrastructure,” said Rezaee. “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 1,110 degrees Celsius 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 sulphuric acid and heated to 250 degrees Celsius 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 neutralise the acid and purify the metal.

“Each step of the conventional method, especially the high-temperature treatment, emits a substantial amount of carbon dioxide,” said Rezaee. “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.”

Rezaee and his team realised they could eliminate the need for this phase transformation.

“We used thermodynamic modelling to understand how the lithium-bearing minerals might interact with different chemical agents, and then validated those predictions through laboratory experiments,” said Rezaee. “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 to cut the processing time to 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 non-acidic, it also eliminates the need for the chemical additions that conventional lithium extraction requires. According to Pen State, the researchers can immediately add a compound that solidifies the lithium so that it can be collected easily.

Rezaee said the process can also work to extract rubidium and cesium, which are used in electronics, quantum computing, solar panels, atomic clocks, and satellite navigation systems. 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 team’s findings are detailed in Chemical Engineering Journal.