With roots in fundamental research conducted at Princeton, a new startup is upending decades-old approaches for the way the world extracts lithium and other materials, including nitrate and potash.

The company, Princeton Critical Minerals (formerly PureLi), which emerged from the University’s ecosystem for innovation and entrepreneurship, has developed a technology for boosting minerals production from evaporation ponds. These ponds currently generate around 40% of the world’s lithium and most of its naturally occurring nitrate.

The technology is a black disc with a special anti-fouling coating, and it floats on the ponds’ surface like a lily pad. It effectively doubles the amount of incoming sunlight converted to thermal energy, accelerating the evaporation process and mineral production.

As Z. Jason Ren, a professor of civil and environmental engineering and the Andlinger Center for Energy and the Environment (ACEE), describes it, PCM’s technology is like adding a second sun to conventional, open evaporation ponds.

“When sunlight hits a traditional evaporation pond, the solar energy is dissipated across the entire pond — the process is less than 50% efficient,” said Ren, who is also a co-founder and chief scientist at PCM. “Our technology is over 96% efficient at converting that incoming sunlight into thermal energy to speed up evaporation in a real-world environment.”

In field pilot tests at evaporation ponds in northern Chile, the team, which partnered with chemical company Sociedad Química y Minera de Chile (SQM), found that their technology boosted evaporation rates when compared to open ponds by anywhere between 40% and 122%, depending on the composition of the brine in the pond.

Because the technology raises the production efficiency of existing ponds, the PCM team said it could alleviate the need to construct additional evaporation ponds — which can sprawl to many square miles in size — to meet the world’s growing demand for lithium and other critical minerals that power today’s clean energy technologies and support modern agriculture. Similarly, any new project could be more compact, with a smaller spatial footprint and reduced environmental impact.

“In many ways, the processes for mineral extraction are the same today as they were three decades ago,” said Sean Zheng, PCM’s chief executive officer and a former distinguished postdoctoral fellow at ACEE. “Our technology could really revolutionize the conventional approach to critical minerals extraction.”

From research to real-world impact

The research was featured on the cover of the February issue of the journal Nature Water.

Image courtesy of Nature

In an article published Feb. 10 in Nature Water (and featured on the cover of the journal’s February edition), Ren and Zheng recounted PCM’s journey from research idea to real-world impact.

The company traces its origins to when Zheng joined Ren’s group as a distinguished postdoctoral fellow at the Andlinger Center for Energy and the Environment. There, Zheng aided investigations into technologies for accelerating evaporation in brine and other salty waters.

“It really started as fundamental research — we published a scientific paper on the technology and evaporation processes involved,” Zheng said. “But we also felt that this technology was something that could make an impact. We wanted to find a way to bring it beyond the lab.”

Central to making that transition were the abundant resources at Princeton available to researchers engaged in innovation and entrepreneurship, including programs supported by the University endowment and other gifts for entrepreneurial initiatives at the Office of Innovation and the Keller Center for Innovation in Engineering Education.

Zheng and Ren participated in the National Science Foundation’s I-Corps program and Princeton’s IP Accelerator Program, which helps researchers gain insights into market needs and refine their innovations for practical use. Princeton University is the lead institution of the I-Corps Northeast Regional Hub.

“I-Corps and the IP Accelerator provided us with a new perspective on the questions we still needed to address about our work,” Ren said. “When we talked to potential customers as part of the I-Corps program, for example, we found that many aspects of the technology that seemed interesting to us as researchers were less important to industry.”

Zheng also pointed to his participation in the inaugural cohort of the START Innovators program as an opportunity to transition from academic research into entrepreneurship. The program, part academic fellowship and part startup accelerator, allowed 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,” said Craig Arnold, vice dean for innovation and University innovation officer. “Professor Ren has shown a very successful example of the ways in which one can leverage a combination of different programs and opportunities within the Princeton Innovation ecosystem to accelerate this translation.”

Sean Zheng presented the team’s work at the 17th annual Innovation Forum hosted by the Keller Center in 2022, winning first prize in the STEM category.

Photo by

Bumper DeJesus, Andlinger Center for Energy and the Environment

The team also participated in the Keller Center's Design for Impact program, which helps researchers translate scholarly research into real-world impact. The program provides not only financial support but also allows researchers to work hand in hand with experts who can help prepare their ideas for commercialization.

“We ask them complex questions that may fall outside a researcher's traditional scope but are essential for translating academic innovations into successful outcomes,” said Nena Golubovic, the director of the Design for Impact program in sciences and engineering.

PCM was formally created in 2023. The company participated in a cohort of the HAX program, a pre-seed startup development accelerator headquartered in Newark, New Jersey, and formed a partnership with the Chilean company SQM to pilot their technology.

“We’ve been moving very fast,” Zheng said. “In less than two years, we’ve moved from testing out small prototypes in kiddie swimming pools to building commercialization-ready products that we’ve deployed at actual mineral production facilities in South America.

“Princeton provided the foundation, ecosystem, and resources that have taught us the skills and knowledge we need to succeed as a small business,” he added.

New partnerships, new research directions

After successful fundraising and several pilot demonstrations in northern Chile, PCM is now in the early stages of commercialization. And though the projects with SQM have proven the technology’s technical and economic feasibility, Ren said they have also opened new research questions for his lab group at Princeton.

For example, the team observed that Lilypad-enhanced ponds maintained higher surface temperatures, with limited heat transfer to the bottom, compared to the more even heat distribution in open ponds. Because temperature impacts mineral solubility, Ren said the field demonstrations sparked new inquiries into brine chemistry to further optimize the evaporation process.

The team at Princeton Critical Minerals (formerly PureLi) participated in a cohort of the HAX program, a pre-seed funding startup development accelerator headquartered in Newark, New Jersey.

Photo courtesy of Z. Jason Ren

“These questions only emerged once we saw the results of the field tests,” Ren said. “If we had kept our work in the lab, these new directions might never have come up.”

In addition to providing Ren with new directions for his scholarly research, he said his efforts with PCM have helped him expand what he sees as the impact of his work, beyond traditional metrics such as a high number of publications in top-tier journals.

 “I want to share our journey so others might come to realize, ‘Hey, this is something I can also do,’” he said.

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The article, “Interfacial solar evaporation for sustainable brine mining,” was published Feb. 10 in Nature Water and was featured on the cover of the journal’s February edition. In addition to Zheng and Ren, co-authors include Beatriz Oelckers of Sociedad Química y Minera de Chile (SQM) and Aashish Khandelwal of Princeton Critical Minerals.