Scientists have made a surprising discovery about the chemistry of lithium-rich salty waters, known as brines, found in some of the world’s most important lithium deposits.
A new study published in Science Advances reveals that these brines have a unique chemical makeup, very different from seawater and other common salty waters.
This discovery could have major impacts on how lithium is mined and how wastewater is managed.
Lithium is a crucial resource in the renewable energy industry, especially for making batteries that power electric vehicles and store solar and wind energy.
About 40% of the world’s lithium is mined from salt flats—also called salars—in the Andes Mountains of South America and on the Tibetan Plateau. These areas are dry, high-altitude regions where lithium is dissolved in underground pools of extremely salty water.
The research team, led by Professor Avner Vengosh at Duke University, studied the chemistry of brines at the Salar de Uyuni in Bolivia, home to the largest known lithium brine deposit.
What they found was unexpected: the acidity or alkalinity (pH) of these brines isn’t controlled by the usual suspects like carbonate molecules, which are typically in charge of balancing pH in natural waters. Instead, boron—a less commonly discussed element—plays the leading role.
Using chemical analysis and computer modeling, the researchers showed that various forms of boron, such as boric acid and borates, determine the pH of these brines. In natural underground brines, the pH is close to neutral.
But as the brine is pumped into evaporation ponds—a common method used to concentrate lithium—the boron becomes more concentrated. This leads to chemical reactions that lower the pH, making the solution more acidic.
Gordon Williams, a PhD student and the study’s lead author, explained that evaporation weakens the usual carbonate buffering system and gives boron complete control over the brine’s chemical behavior.
Postdoctoral researcher Paz Nativ added that their modeling work helped reveal how different boron molecules contribute to this process.
To test if this pattern was unique to Bolivia, the team compared more than 300 brine samples from other lithium-rich salt flats in Chile, Argentina, and Tibet. The results were consistent—boron was also the main force shaping the pH in these brines.
This study is the first to highlight boron’s critical role in lithium brine chemistry.
The findings could help mining companies refine their lithium extraction methods, improve efficiency, and better handle the environmental challenges that come with wastewater. In the race to power a greener future, understanding these hidden chemical processes could make a big difference.
