Lithium discovery has vast implications for future mining operations

Lithium is one of the most important minerals powering the world’s clean energy transition. Found in the batteries of electric vehicles, laptops, and smartphones, it is increasingly in demand all over the world.

But before lithium makes its way into devices and cars, it often begins its journey in some of the world’s most extreme environments, such as massive salt flats nestled high in the mountains.

Roughly 40% of the world’s lithium is extracted from brine – a type of super-salty water that is found beneath salt pans in the Andes of South America and the Tibetan Plateau in Asia.

A new study from Duke University sheds light on a surprising detail: these lithium-rich waters have a completely different chemical makeup than other saline waters, like seawater.

Not your average saltwater

In these isolated, high-altitude regions, lithium lies beneath the earth’s surface in brine pools. These pools are extremely salty, but they behave very differently from water in the ocean.

“We discovered that the pH of brines in these regions is almost entirely driven by boron, unlike seawater and other common saline waters. This is a totally different geochemical landscape, like studying an extraterrestrial planet,” said Avner Vengosh, Chair of the Division of Earth and Climate Sciences at Duke University’s Nicholas School of the Environment, who oversaw the research.

pH is a measure of how acidic or alkaline a solution is. In most natural waters, this balance is controlled by carbonate molecules.

But what the researchers found at Bolivia’s Salar de Uyuni – a giant salt pan known to hold the world’s largest lithium brine deposit – was something else entirely.

Lithium brine and mining

The traditional method for extracting lithium from salt pans is straightforward but slow. Brine is pumped from underground into shallow ponds.

Over time, the water evaporates, and the remaining liquid becomes more concentrated with lithium, boron, and other salts. Eventually, lithium is separated out in a processing plant.

But this method triggers important chemical changes.

Acidity changes in ponds

The team analyzed both the natural brine and samples taken from the evaporation ponds. They noticed a striking contrast. The underground brine samples were close to neutral pH, but the pond samples were far more acidic.

Using computer models, they identified the culprit: boron.

“Through a chain of geochemical reactions, the carbonate alkalinity is diminished in the brine from the Salar de Uyuni, while boron alkalinity becomes predominant,” explained lead author Gordon Williams, a Ph.D. student in the Vengosh Lab.

The natural brine contains a lot of boron, existing as boric acid and borate compounds. As water evaporates from the ponds, these compounds become more concentrated. Boric acid begins to break down and it releases hydrogen ions that lowering the pH.

Boron, brine, and lithium

To better understand boron’s behavior, the researchers built detailed models to measure how its molecular forms contribute to the brine’s alkalinity.

“The integration of the chemical analysis with geochemical modeling helped us to quantify the different molecular structures of boron that contribute to alkalinity in these lithium brines,” added Paz Nativ, a postdoctoral researcher in the Vengosh Lab.

The team didn’t stop with Bolivia. They analyzed data from more than 300 brine samples across the Lithium Triangle – Chile, Argentina, and Bolivia – as well as the Tibetan Plateau. In most cases, boron had the greatest effect on the water’s pH and alkalinity.

“In addition to the new data we generated, we compiled a geochemical database of lithium brines from around the world and consistently found that boron is often the predominant component in brine alkalinity and controls brine pH,” explained Williams.

These results supported reinforced the findings from the Salar de Uyuni in Bolivia.

What brine means for lithium mining

This is the first time scientists have shown how boron shapes the chemical evolution of brines during lithium mining.

Understanding this unique chemistry could help make lithium extraction more efficient and environmentally responsible.

As demand for lithium continues to rise, knowing how to manage the chemistry of these valuable waters – especially their acidity and boron content – could shape the future of clean energy.

The full study was published in the journal Science Advances.

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