An Alternative To Mining For Minerals
When it comes to producing the key minerals to feed the world’s industries, there are really only 3 possible sources: mining rocks, recycling, and purifying dissolved minerals. For materials like iron and aluminum, traditional mines are the primary suppliers, with recycling also contributing.
However, for materials like lithium, one of the primary sources is brines, mineral-rich waters that must be evaporated to collect the minerals they contain. A similar method is often used for the production of the two most important fertilizers: nitrates and potash.
This method requires massive evaporation ponds that cover thousands of acres, pushing a heavy environmental cost to the local ecosystems.
Source: SQM
So far, it has been achieved by relying solely on the Sun’s rays to warm the ponds and evaporate the water. This is far from an efficient process, hence the massive surfaces required.
This might just be changing, thanks to a new material that could speed up evaporation, developed by researchers at Princeton University and in collaboration with lithium production giant Sociedad Química y Minera de Chile (SQM +2.61%).
They published their invention in Nature Water1, under the title “Interfacial solar evaporation for sustainable brine mining”.
Mass Producing Lithium
(Not-So-Sustainable) Green Energy
When not extracted from rocks (spodumene deposits), lithium is mostly found in mineral brines, mixed with other salts and dissolved minerals. The brine is mostly extracted from underground waters or created by leaching the lithium from mineral-rich deposits with fresh water.
Currently, tens of thousands of hectares of solar ponds are in use in the world for extracting lithium, with Chile having 6,000 hectares (14,800 acres).
This method is putting extreme pressure on the water supply of these regions. Making matters worse, lithium-rich areas are generally deserts, which is why lithium is concentrated in economically viable deposits in the first place. Therefore, the limited water available might be entirely diverted toward the lithium industry, putting local ecosystems and communities at risk.
Energy Consumption
These evaporation ponds are a method to harness solar energy “for free”. It is a superior option to alternatives using electricity, such as mechanical vapor compression or ultrahigh-pressure reverse osmosis.
While likely more ecological, these electricity-based methods would be impossible to implement at scale. For example, just the Chilean evaporation ponds are harnessing 65 TWh of solar energy, exceeding 70% of Chile’s total annual production (~90 TWh per year).
A significant issue is that, even though it is inexpensive, the evaporation pond method is far from efficient. Less than half of the solar energy is converted into thermal energy, contributing to evaporation.
This is where the invention of Princeton’s researchers comes in.
Fertilizers
Not only lithium but also fertilizers can be produced through evaporation ponds. Notably, SQM produces yearly 1.5 million tons of nitrate salts from caliche ore and salar brines.
Source: SQM
This is part of a complex chemical mixture that SQM extracts from brines, including lithium chloride, potassium chloride, magnesium chloride, boric acid, and potassium sulfate. The potassium is then mixed with it to form potassium nitrate.
While not a significant source of fertilizer compared to direct mining or the synthesis of nitrogen-based fertilizers using natural gas (Haber-Bosch process), this is another environmentally impactful production process that could be improved by more efficient evaporation ponds.
Optimizing Evaporation
Previous Discoveries
The latest R&D work on boosting evaporation pond efficiency is built on previous work by the same researchers and others in this field. They had worked on the phenomenon called interfacial solar evaporation (ISE).
The key concept of ISE is to utilize a highly light-absorbing material to capture nearly 100% of solar radiation while also absorbing the salty, mineral-rich water.
Source: ResearchGate
Extra progress has also been made to avoid salt accumulation and crystallization, which would reduce efficiency over time, notably salt backflow enhancement, Janus structural designs, and directional crystallization.
A Public-Private Partnership
This work was done as part of the University’s START Innovators program. The program, a combination of academic fellowship and startup accelerator, enabled researchers to continue developing their technology while creating a business plan and building early-stage ventures.
“Helping to cultivate an ecosystem in which our faculty and researchers can effectively translate their technologies to the commercial sector is a core function of the Office of Innovation.”
Craig Arnold – Vice Dean for Innovation and University Innovation Officer.
This approach is looking to speed up the transfer of technology from lab ideas to industrial scale and translate better the technical skills of the academic researchers into practical applications.
“What we’re able to do with researchers like Professor Ren and his team is to help redirect how they think about their ideas. Our goal is to radically shift participants’ perspectives, so they leave our program with a completely different perspective than when they entered.
We ask them complex questions that may fall outside a researcher’s traditional scope but are essential for translating academic innovations into successful outcomes.”
Nena Golubovic – Director of the Design for Impact program in Sciences and Engineering
This seems to have worked, with the technology going from “small prototypes in kiddie swimming pools” to testing commercialization-ready products in mineral production facilities in South America in less than 2 years.
“Princeton provided the foundation, ecosystem, and resources that have taught us the skills and knowledge we need to succeed as a small business.”
Sean Zheng – Princeton Critical Minerals’ CEO (formerly PureLi)
Boosting Efficiency
While the previous prototype used wood as a water-carrying material, the researchers invented twisted cellulose fiber crystallizers. It enables not only fast water evaporation but also spatially separated crystallization for selective lithium recovery.
They also used proprietary coatings for our carbon-based materials, enabling fast evaporation, mineral separation, and antifouling properties.
The startup Princeton Critical Minerals tested its first prototype in a real-life lithium evaporation pond owned by SQM, shaped like a lily pad floating at the surface of the water.
Source: ResearchGate
When observed with a thermal camera, it is clear that the water surface is a lot hotter, with especially hotspots in a special zone of the artificial lily pad. The design proved capable of converting 96% of solar energy into thermal energy, compared to the 50% efficiency of open ponds.
Source: ResearchGate
This overall radically improved the evaporation rate, which doubled on average ( 40–122% increase depending on the brine concentrations). It also had the effect of strongly reducing water loss to the bottom of the pond, as the process happened a lot quicker.
Source: ResearchGate
Further Research
The thermal camera data proved that the key way the artificial lily pads work is by keeping the sun’s heat at the surface of the pond, where it actually performs evaporation, instead of at the bottom, where the heat gets lost.
As temperature impacts mineral solubility, it could be that further tweaking of the temperature in the lily pads’ surface could improve lithium production even further.
“These questions only emerged once we saw the results of the field tests. If we had kept our work in the lab, these new directions might never have come up.”
Z. Jason Ren – Professor of civil and environmental engineering
Another step will be to initiate mass manufacturing of the artificial lily pads and explore the economics of the device, as well as potential long-term business models for Princeton Critical Minerals.
Lithium Evaporation Companies
Sociedad Química y Minera de Chile S.A.
Sociedad Química y Minera de Chile S.A. (SQM +2.61%)
SQM is the second-largest lithium mining company in the world, with its assets in Chile and lithium representing the bulk of the company’s business. It is also the market leader in producing potassium nitrate of natural origin and sells specialty chemicals like iodine, potassium chloride, boric acid, and magnesium chlorides.
Source: SQM
In April 2023, the company had to face a move by Chile threatening a partial nationalization of the country’s lithium industry. Past the initial shock, further details on the plan clarified that the country still intended to attract private foreign investment.
More specifically, national lithium company Coldeco is renegotiating a contract with SQM, and other lithium deposits will be offered for exploitation. The existing contract will nevertheless be respected and run until 2030.
Because the negotiations are ongoing, very little information is available, and it is hard to predict the long-term future of SQM. Still, Chile is a country highly dependent on mining for its economy, and the initial backlash against the nationalization plans, impacting not only confidence in lithium but in all mining, has forced the government to limit its ambitions (for now?).
The threat of nationalization was followed by a durable decline in international lithium prices, which has caused a decline in the company’s stock price, down from its peak at the end of 2022.
Source: Carbon Credit
Lithium had sales volumes growth (+13%), significantly lower year-on-year average sales prices (-41%) in 4Q2024 vs 4Q2023
As a result of low lithium prices, the company has made a lot more revenues in 2024, proportionally, from other products than in the past, with iodine responsible for 39% of gross profits.
Source: SQM
This can be seen as either reflecting the real risk of the company or as an opportunity to grab investors willing to take the risk and collect a solid dividend yield.
Like for all lithium investments, investors will want to be familiar with the EV landscape (demand and the potential of innovative chemistry like sodium-ion batteries, not using lithium) and expect the high volatility of lithium prices to persist for the foreseeable future, even if more downside risks seem somewhat priced in.
(You can read more about lithium and batteries in our articles “Is Lithium Demand Set to Plummet with New Sodium-Ion Batteries?”, “Does Arkansas Hold the Answer to Our Lithium Needs?” and “Investing in Nobel Prize Achievements: Lithium-Ion Batteries To Power The World”.)
Latest on Sociedad Química y Minera de Chile S.A.
Studies Referenced:
1. Zheng, S., Oelckers, B., Khandelwal, A. et al.(2025). Interfacial solar evaporation for sustainable brine mining. NatureWater 3, 135–137. https://doi.org/10.1038/s44221-025-00394-y