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A team of engineers at Monash University has developed a method for extracting lithium from solid salt mixtures that eliminates the need for freshwater and relies on common organic solvents powered by solar energy.
The technique, called solar-driven selective dissolution (SSD), represents a departure from both conventional evaporation-pond methods and newer direct lithium extraction (DLE) technologies, both of which consume large volumes of water and chemicals.
Published in the journal Environmental Science & Technology, the research was led by Professor Huanting Wang, Dr Zhikao Li and PhD candidate Pan Liu from the Department of Chemical and Biological Engineering at Monash University.
How The Process Works
Rather than attempting to pull lithium directly from liquid brine – the approach taken by most existing methods – the Monash team’s process starts by evaporating brine in a single solar-driven pond to produce a complete solid salt mixture.
That solid mixture is then treated with industrial ethanol, which selectively dissolves lithium chloride while leaving behind sodium chloride, potassium chloride, calcium chloride and boron and sulfate salts, all of which have low solubility in ethanol.
A second step uses an acetone-ethanol mixed solution to separate lithium from magnesium chloride, which is also soluble in ethanol but has low solubility in acetone.
The result is a lithium-rich salt that can be processed into battery-grade lithium carbonate with a purity of 99.7 per cent.
“This work shows that lithium can be efficiently separated from complex salt mixtures using simple organic solvents, without relying on freshwater or highly chemical-intensive processes,” Dr Li explained.
The Problem With Current Methods
Salt-lake brines are one of the largest lithium reserves in the world, but the conventional method of extracting lithium from them is slow and wasteful.
Traditional evaporation-precipitation processes require a series of ponds where different salts crystallise out in sequence over a period of one to two years. The process demands large land areas, consumes between 100 and 800 cubic metres of freshwater per ton of lithium carbonate produced, and results in 30 to 50 per cent lithium loss through coprecipitation with other salts.
On average, traditional methods also generate around 115 tons of solid waste per ton of lithium carbonate, creating environmental issues in the arid regions where salt lakes are typically found.
Newer DLE technologies using adsorption, solvent extraction and membrane separation have shown potential but come with their own drawbacks. Their freshwater consumption can exceed ten times that of traditional methods, and their performance often degrades when dealing with the low lithium concentrations, high salinity and complex ionic compositions found in real-world brines.
Many DLE processes also produce spent brine containing chemical reagents that cannot be safely returned to the environment.
Why Ethanol And Acetone
The core of the Monash method relies on a simple chemical principle: different salts have different solubilities in organic solvents depending on the charge density of their ions and the polarity of the solvent.
Water, with its high dielectric constant of 80.1, dissolves most salts readily, making separation difficult. Ethanol, with a dielectric constant of 25.1, is far more selective.
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In industrial ethanol (95 per cent ethanol with 5 per cent water), lithium chloride has a saturation solubility of 191.64 grams per litre. By contrast, sodium chloride dissolves at just 1.70 grams per litre and potassium chloride at 0.66 grams per litre. Sodium tetraborate and sodium sulfate – the forms in which boron and sulfate impurities typically exist – are almost completely insoluble, at 0.39 grams per litre and 0.003 grams per litre respectively.
The researchers found that the presence of 0 to 10 per cent water in ethanol had little effect on salt solubility, meaning industrial-grade ethanol can be used rather than expensive high-purity solvent, reducing costs.
For the magnesium separation step, acetone was chosen because it lacks hydrogen-bond donors, meaning it cannot effectively replace the bound water surrounding magnesium ions and therefore keeps magnesium chloride largely insoluble while still dissolving lithium chloride.
Testing With Real Brine Compositions
The team tested their process using synthetic brines matching the compositions of two well-known South American salt lakes: Salar De Uyuni in Bolivia and Hombre Muerto in Argentina.
For Salar De Uyuni, the process achieved total lithium recovery of 92.31 per cent with sodium removal of 99.97 per cent, potassium removal of 99.72 per cent, calcium removal of 82.18 per cent, boron removal of 99.54 per cent and sulfate removal of 100 per cent.
For Hombre Muerto, total lithium recovery reached 94.25 per cent with sodium removal of 100 per cent, potassium removal of 99.98 per cent, calcium removal of 86.81 per cent, boron removal of 97.76 per cent and sulfate removal of 100 per cent.
Those lithium recovery figures represent roughly two to three times the recovery achieved by conventional processing methods.
The boron removal rates are particularly notable. Conventional boron-precipitation solar ponds typically achieve around 70 per cent removal, while the SSD process exceeded 97 per cent in both test cases. Boron contamination has long been one of the most persistent challenges in producing battery-grade lithium, as it forms stable complexes with lithium ions and can become incorporated into lithium carbonate crystal structures during crystallisation.
Solar-Powered Solvent Recycling
A key element of the approach is the recycling of organic solvents using interfacial solar evaporation, building on a concept developed by the Monash team more than a decade ago.
The researchers used a commercially available black polyurethane sponge as the photothermal material. The sponge, which absorbs 95.79 per cent of incoming solar radiation, floats on the surface of the solvent and converts sunlight into heat to accelerate evaporation.
Under standard one-sun illumination, the sponge achieved evaporation rates of 6.32 KG per square metre per hour for industrial ethanol and 14.90 KG per square metre per hour for pure acetone. Those rates increased further under stronger illumination or when a light breeze was introduced.
The evaporation enthalpies of industrial ethanol and pure acetone in the sponge system were measured at 654.13 kilojoules per KG and 357.90 kilojoules per KG respectively, both well below water’s evaporation enthalpy of 1,694.32 kilojoules per KG. That lower energy requirement is what makes solar-powered solvent recovery practical.
Using a closed recovery system with a cold trap for condensation, the researchers achieved solvent recovery rates of 99.66 per cent for industrial ethanol, 99.75 per cent for the acetone-ethanol mixture and 99.71 per cent for pure acetone. Chemical analysis confirmed the recovered solvents retained their original composition and contained no residual ions.
The recovered solvents were recirculated through ten successive extraction cycles with no measurable decline in lithium recovery, solvent quality or magnesium-to-lithium ratio in the product.
Cutting The Timeline
The researchers estimate that the combination of photothermal evaporation and the SSD process could reduce lithium production timelines from the 24 months typical of conventional methods to approximately 100 days.
That estimate accounts for the intermittent nature of solar energy, including day-night cycles, weather variability and seasonal fluctuations.
The researchers acknowledged that real-world performance of solar-driven systems can deviate from laboratory results, but noted that engineering strategies such as increasing evaporation area, improving photothermal conversion efficiency or integrating auxiliary heating could help address those challenges.
Economic Case
A technoeconomic analysis conducted by the team found that traditional evaporation-precipitation technology yields a profit of approximately $6,086 USD per ton of lithium carbonate.
For Hombre Muerto brine, which has a lower magnesium concentration and therefore requires fewer processing steps, the SSD process increased that profit to $20,219 USD when treating the same volume of brine – a 232 per cent increase.
For Salar De Uyuni, which has a higher magnesium concentration requiring an additional acetone separation stage, the profit was lower but still reached $13,166 USD per fixed brine volume.
The SSD process avoids costs associated with freshwater consumption and chemical reagents, and it generates no spent brine, eliminating waste disposal expenses.
Environmental Considerations
The process eliminates freshwater consumption for the separation of interfering ions, which addresses a growing environmental concern in arid regions where lithium brines are found. Traditional methods consume 20 to 50 cubic metres of freshwater per ton of lithium carbonate, while some DLE technologies require over 100 cubic metres.
The researchers noted that the solar evaporation step used to produce solid salts from brine could itself enable the recovery of freshwater, an approach that has shown commercial potential in recent large-scale demonstrations.
The use of volatile organic solvents does introduce safety and environmental considerations related to flammability and potential volatile organic compound emissions. However, the researchers pointed out that both ethanol and acetone are classified as “usable” solvents under the GSK Solvent Sustainability Guide, with acceptable safety, health and environmental profiles. In a practical deployment, the system would operate in a closed configuration with controlled vapour recovery.
“By coupling these processes, we achieve high recovery rates and very high solvent reuse, which significantly reduces environmental impact while maintaining strong performance,” Dr Li noted.
What Comes Next
The researchers described their work as a proof-of-concept solid-state separation strategy. Future studies will focus on validation using real salt-lake samples and integration into full process chains.
The team has filed an Australian Provisional Patent Application for the technology.
The research was supported by the Australian Research Council through Professor Wang’s Australian Laureate Fellowship.
The approach represents a different way of thinking about the lithium extraction problem: rather than trying to separate lithium from a complex liquid, the method works with solids, where differences in solubility can be exploited more cleanly.
Whether the technique can scale to industrial volumes and operate reliably under real-world conditions in remote, arid environments remains to be demonstrated, but the laboratory results suggest it addresses several of the key limitations that have constrained lithium extraction from brines for decades.
Last Updated on June 16, 2026 by Nick Ross
