In the quest for sustainable energy solutions, lithium has emerged as a critical mineral, underpinning the rapidly expanding electric vehicle market and renewable energy storage technologies. Recent research published in Science Advances on May 23, 2025, unveils groundbreaking insights into the chemical mechanisms governing lithium-rich brine deposits found in expansive salt flats, known as salars. These environments, located primarily in the Andes Mountains of South America and the Tibetan Plateau in Asia, harbor some of the planet’s largest lithium resources. What makes these brines exceptional is their unique chemistry, distinctly different from the saline waters of typical oceans or other saltwater bodies.
Traditional understanding holds that carbonate chemistry largely dictates the alkalinity and pH of natural waters. However, this new study overturns that conventional wisdom by demonstrating that boron plays the dominant role in controlling pH within lithium-bearing brines. This discovery was spearheaded by a team of researchers led by Avner Vengosh from Duke University’s Nicholas School of the Environment, who describe the geochemical environment of these brines as almost extraterrestrial due to their stark chemical differences.
At the heart of the study lies the Salar de Uyuni, the world’s largest salt flat, located on a plateau in Bolivia. Beneath its thick salt crust lies a vast reservoir of lithium-rich brine, formed under hyper-arid and high-altitude conditions. Mining operations there pump this underground brine into a series of evaporation ponds where water gradually evaporates, concentrating lithium and associated elements like boron to extractable levels. Understanding the chemical nuances of this brine is crucial for improving lithium recovery efficiency and developing environmentally sustainable processing methods.
The research reveals that, unlike seawater where carbonate ions strongly influence pH, in these lithium-rich brines, the alkalinity is predominantly controlled by boron species, including boric acid and borates. The distribution of these boron compounds governs the brine’s pH balance, which remains near neutral in natural brines but becomes markedly acidic in evaporation ponds due to the intensified concentration and chemical transformation of boron during evaporation.
This pH shift is critical because it impacts lithium extraction chemistry and the stability of other dissolved ions. Computer simulations conducted as part of the study indicated that as evaporation progresses, boric acid breaks down to release hydrogen ions, thus lowering pH and altering the chemical landscape of the brine. These findings challenge existing notions about brine chemistry and open new avenues for optimizing lithium extraction processes by managing boron chemistry more precisely.
Lead author Gordon Williams, a doctoral student working under Vengosh’s guidance, emphasizes that the shift from carbonate to boron alkalinity represents a fundamental change in how these brines maintain chemical equilibrium. This change has profound implications, especially as lithium production continues to scale up globally. Insights into the underlying molecular structures of boron compounds and their role in buffering pH provide a new perspective on designing mining techniques and waste management strategies tailored to these unique chemical systems.
Supporting researchers, like Paz Nativ, highlighted the integrative approach combining chemical analyses with geochemical modeling, which allowed the team to quantify boron species’ contributions to brine alkalinity. This dual approach confirmed that boron’s influence supersedes that of carbonate ions not just at Salar de Uyuni but also across more than 300 lithium brine samples from other major salt flats in the Lithium Triangle region—Chile, Argentina, and Bolivia—and the Tibetan Plateau, suggesting a global pattern.
The broader implications of this discovery stretch beyond academic interest. By delineating the fundamental role of boron in lithium brine chemistry, mining companies can enhance their process controls, reducing environmental impacts and increasing lithium yield efficiency. Additionally, these insights are critical for managing wastewater and tailings resulting from brine evaporation, potentially mitigating acidification hazards stemming from elevated boron concentrations.
The phenomenon that boron governs pH changes also narrows the knowledge gap in geochemistry regarding saline water systems that deviate from classical oceanic models. Understanding these exotic chemical landscapes enables scientists to better predict how lithium resources respond to environmental changes and extraction pressures. In essence, studying these brines is akin to exploring geochemical planets within our own Earth, offering a rare window into complex mineral-water interactions shaped by extreme environmental conditions.
Funding from Duke University’s Climate Research Innovation Seed Program (CRISP), the Josiah Charles Trent Memorial Foundation Endowment Fund, and the Graduate School Dissertation Research Travel Award supported this pioneering work. This study exemplifies how cross-disciplinary collaboration in geochemistry, environmental science, and resource engineering can unveil new dimensions in mineral extraction science with broad relevance to global energy transitions.
As the global demand for lithium escalates in tandem with the battery storage revolution, understanding the intricate role of boron in controlling the pH of lithium brines holds the potential to transform both the economic viability and environmental sustainability of lithium mining. Future research, driven by these novel findings, may well lead to more efficient, cleaner, and safer methods to harness this essential resource, reinforcing the strategic importance of geochemical research in addressing climate and energy challenges worldwide.
Subject of Research: The geochemical role of boron in controlling the pH and alkalinity of lithium-rich brines found in salt pans.
Article Title: The role of boron in controlling the pH of lithium brines
News Publication Date: 23-May-2025
Web References: DOI: 10.1126/sciadv.adw3268
Image Credits: Photo by Avner Vengosh/Duke University Nicholas School of the Environment
Keywords
lithium brines, boron chemistry, pH control, alkalinity, salt pans, Salar de Uyuni, geochemical modeling, renewable energy materials, lithium extraction, brine evaporation, environmental geochemistry, mineral resources
