A simple laboratory experiment at the University of Michigan has revealed an unexpected way to extract lithium from brines long dismissed as uneconomical.
The discovery could unlock vast lithium resources trapped in magnesium-rich waters, offering a more sustainable route to meet rising demand from batteries, electric vehicles, and renewable energy systems.
Lithium supply already faces mounting pressure. Mining from hard rock remains costly and environmentally damaging, while conventional brine extraction depends on vast evaporation ponds that consume land and water.
Although brines hold more than half of the world’s lithium, most remain unused because high magnesium levels complicate extraction.
“In some natural brines, the conventional approach isn’t economical, so people aren’t utilizing the resource,” said Jovan Kamcev, an associate professor of chemical engineering and the corresponding author of the study published in Nature Chemical Engineering.
Magnesium problem in brines
Lithium-rich brines form naturally in salty lakes or underground reservoirs beneath dry lake beds.
Producers typically pump brine into shallow ponds and rely on sunlight to evaporate the water.
As salinity increases, salts crystallize, and chemicals help isolate lithium.
Magnesium disrupts this process. Its chemical similarity to lithium causes both elements to form solids together during evaporation.
When magnesium concentrations rise above six times lithium levels, operators must add extra chemicals to remove it.
That increases costs and produces more waste.
Because of this challenge, most magnesium-rich brines qualify as low quality for lithium extraction. As a result, production concentrates in a few South American salt flats and hard rock mines.
Supply constraints loom ahead. S&P Global estimates lithium demand could outpace existing supply pipelines by 2029.
Tapping underused resources like the Smackover Formation brines in Arkansas could ease the strain, but only if new extraction methods reduce cost and environmental impact.
Accidental membrane breakthrough
The Michigan team discovered a new approach while testing membranes designed for electrodialysis.
Instead of applying electricity, researchers placed pure water on one side of a negatively charged membrane and brine on the other. Lithium ions crossed into the pure water.
Magnesium stayed behind.
“This separation strategy can recover lithium without the water-intensive steps that pose sustainability concerns in current technologies,” said Lisby Santiago-Pagán, a doctoral student and co-first author of the study.
The behavior surprised the team. In traditional electrodialysis, magnesium should move faster because it carries a stronger positive charge.
“This discovery was kind of an accident in the lab,” said Kamcev. “We really didn’t understand it at first.”
The explanation lies in charge balance.
Chloride ions diffuse through the membrane, and lithium follows to balance the charge. Magnesium instead binds strongly to the membrane’s negative charges and gets trapped.
When electricity enters the system, magnesium gains enough energy to cross and contaminate the solution.
The method cannot separate lithium from ions with the same charge, such as sodium.
Researchers suggest combining it with evaporation, selective adsorbents, or lithium-precipitating chemicals.
“The next step is for researchers to do a process and techno-economic analysis to see what processes can actually work together,” said Harsh Patel, a doctoral student and co-first author.
The team has applied for patent protection and is seeking industry partners to bring the technology to market.
