A University of Rochester research team has developed a solar-thermal desalination process that converts seawater to drinking water with zero brine waste — and can even recover lithium and other valuable minerals in the process.
More than 2 billion people worldwide lack reliable access to safe drinking water, yet the leading methods for converting ocean water into something drinkable come with serious environmental costs. Now, a research team at the University of Rochester has developed a solar-powered desalination technique that eliminates brine waste entirely while also recovering valuable minerals — a potential breakthrough for both global water security and sustainable supply chains.
The work, published in Light: Science & Applications, was led by Chunlei Guo, a professor of optics and physics and senior scientist at University of Rochester’s Laboratory for Laser Energetics. A companion study in the Journal of Materials Chemistry A extends the approach to extract lithium directly from saltwater.
Why Conventional Desalination Falls Short
Reverse osmosis and thermal distillation — the two most widely used desalination technologies — are energy-hungry processes that require chemical pre-treatment of water and generate a byproduct called brine, a concentrated saltwater mixture that is typically pumped back into the ocean. That brine discharge raises local salinity levels, depletes oxygen, and disrupts marine ecosystems. Communities from California to the Middle East depend on these plants, yet the environmental trade-offs have long been a concern among water researchers and policymakers.
Laboratory-scale solar-thermal desalination methods have shown promise as a greener alternative, but they tend to break down when tested with actual ocean water. The reason comes down to chemistry: simulated seawater used in lab settings is typically just water and sodium chloride, which crystallizes in a grainy, porous way that can be rinsed off solar panels easily. Real seawater is far more complex. Magnesium- and calcium-based compounds crystallize in hard, non-porous crusts that clog panel surfaces over time — the same way mineral scale accumulates inside a kettle or a shower head, except seawater carries hundreds of times more dissolved salts than typical tap water.
How the New Technology Works
Guo’s team addressed both the clogging problem and the brine problem by engineering black metal solar panels etched with femtosecond lasers. The laser treatment makes the metal surface super light-absorbing and superwicking — meaning it draws water toward itself with exceptional force. The panel is divided into two regions: an active zone that pulls a thin film of water across its surface, heats it with nearly all available solar radiation, and distills fresh water, and a passive outer zone where salts and minerals accumulate without interfering with the active desalination process.
To keep the active surface from clogging, the team borrowed from an unlikely source of inspiration: the coffee ring effect, a phenomenon familiar to anyone who has ever spilled a cup and watched the liquid dry into a dark ring at the edges. Guo explained the concept simply.
“If you drop coffee on a surface, eventually the water evaporates and there’s a ring left at the outer edge that is the concentrated coffee particles,” Guo said in a news release.
His team engineered the panel’s grooves to exploit this same physics, directing dissolved salts outward toward the passive region.
“We use that same principle to advance the salts to the passive region,” Guo added.
The researchers validated their approach using real water samples collected from the Pacific, Atlantic and Indian Oceans. The panel surface remained self-cleaning throughout, continuously depositing salt crystals in the passive zone without any reduction in efficiency or need for chemical additives.
Turning Waste Into Resources
Perhaps the most striking aspect of the new method is what happens to the salts left behind. Rather than generating liquid brine that must be discharged or processed, the system recovers close to 100% of dissolved solids in solid form — including table salt and, critically, lithium.
Lithium is a key ingredient in the rechargeable batteries that power electric vehicles, laptops and smartphones, and demand for it is surging globally. Current mining operations are both energy-intensive and environmentally damaging.
“Mining lithium from the earth has proven to be very taxing from an energy and environmental standpoint, so pulling lithium directly from saltwater could be a very important future route,” added Guo.
The companion paper shows how embedding hydrogen titanate nanoparticles into the laser-etched grooves of the black metal surface selectively isolates lithium from the mixture of other salts. Using water samples from Utah’s Great Salt Lake, the team extracted roughly half the lithium present — a promising result for a first-generation system.
Why It Matters for Students and Young Professionals
Water scarcity is not a distant problem. Droughts, aquifer depletion and population growth are straining fresh water supplies in parts of the American Southwest, sub-Saharan Africa, South Asia and beyond. At the same time, the electric vehicle boom is driving fierce competition for lithium, with supply chain concerns affecting everything from battery costs to geopolitical tensions. A technology that simultaneously addresses fresh water access and critical mineral recovery — using only sunlight — touches nearly every major sustainability challenge facing the next generation.
Guo and his colleagues at University of Rochester’s Institute of Optics, including senior scientist Subash Singh, alumnus Ran Wei, and doctoral students Luheng Tang, Tainshu Xu and Mingjiang Ma, see the approach as inherently scalable. The current demonstrations are proof-of-concept devices, but the underlying physics do not impose fundamental size limits, suggesting larger installations could be feasible with further development.
The research received funding from the National Science Foundation, the Bill & Melinda Gates Foundation, and the Worldwide Universities Network.
Source: University of Rochester