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Desalination has always carried a hidden cost. For every liter of fresh water a typical plant squeezes out of the sea, it produces a gush of concentrated, chemical-laden brine - and that brine is often piped straight back into the ocean, where its extra salt and heat can choke the life out of the seabed below. Now physicists at the University of Rochester have built a solar device that skips the brine entirely, captures the salt as a dry solid, and - as a bonus - pulls valuable lithium out of the leftovers.
The work appears in two 2026 papers, in Light: Science & Applications and the Journal of Materials Chemistry A, from the lab of Professor Chunlei Guo. Here is how it works, why it is a genuine step forward, and what still stands between it and a working plant.
- Who: Professor Chunlei Guo and colleagues, University of Rochester
- What: a sunlight-powered desalination panel that makes fresh water and captures the salt as a solid - no toxic liquid brine
- How: laser-etched, superwicking black metal that self-cleans salt using the everyday ‘coffee-ring effect’
- Tested on: real water from the Pacific, Atlantic and Indian Oceans
- Bonus: the same panels recovered about 50% of the lithium from Great Salt Lake brine
- Papers: Light: Sci. & Appl. (DOI 10.1038/s41377-026-02315-4) and J. Mater. Chem. A (DOI 10.1039/D5TA08968A), May 2026
1. The brine problem
Reverse osmosis and thermal distillation, the workhorses of modern desalination, are good at making fresh water - but roughly half of what they take in leaves as brine: water that is twice as salty as the sea, often warm and dosed with anti-scaling chemicals. Dumped back offshore, it sinks, spreads along the bottom, and can drive oxygen out of the water, harming seagrass, corals and the creatures that depend on them. Handling that brine is one of the quiet reasons desalination stays expensive and controversial.
2. A panel that cleans itself with the coffee-ring effect
Guo’s group is known for using ultrafast laser pulses to etch metal into a ‘superwicking’ black surface: it absorbs nearly all the sunlight that lands on it and draws water upward in a paper-thin film, exactly where the sun’s heat can flash it into vapor. The hard part has always been salt. As seawater evaporates, salt is left behind, and normally it crusts over the surface and clogs it within hours.
The team’s fix is elegant and everyday. “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 explains. “We use that same principle to advance the salts to the passive region.” Microscopic grooves carry the brine outward to cooler, inactive edges, where the salt crystallizes and is collected as a solid. The evaporating center stays clean, so the panel keeps running - with no added chemicals and, crucially, no liquid brine to dispose of.
| Conventional desalination | This solar panel |
|---|---|
| Produces toxic liquid brine (~half the intake) | Zero liquid discharge - salt captured as dry solid |
| Runs on grid electricity or fuel | Runs on sunlight alone |
| Often needs anti-scaling chemicals | No chemical additives |
| Salt is a disposal problem | Salt becomes a resource - including lithium |
3. The lithium bonus
Because the salt is now a solid you can harvest rather than a liquid you must dump, it becomes a source of minerals. In the companion study, the researchers embedded tiny hydrogen-titanate particles into the panel’s grooves - particles that selectively grab lithium ions. Running the system on brine from Utah’s Great Salt Lake, they recovered about half of the lithium present.
“Mining lithium from the earth has proven to be very taxing from an energy and environmental standpoint,” Guo notes, “so pulling lithium directly from saltwater could be a very important future route.” The same sunlight that makes drinking water, in other words, could also help supply the metal at the heart of the batteries in phones, laptops and electric cars.
Why it matters
The United Nations estimates that about 2.2 billion people still lack safely managed drinking water. A desalination approach that runs on nothing but sunlight, needs no added chemicals, leaves behind no polluting brine, and even yields a valuable mineral is precisely the kind of simple, self-contained technology that could reach communities without reliable power or heavy infrastructure.
What this does not mean (yet)
- It is lab-scale. The papers demonstrate the physics and the salt-handling on modest samples - not a deployed plant supplying a town.
- Scale, durability and cost are the hard part. Getting from a clever panel to real-world output means proving it lasts for years and can be manufactured cheaply at size.
- The lithium recovery was partial - about 50%, not total - and remains a proof of concept.
- The promise is directional. What is exciting is the combination: clean water, no waste stream, and a useful byproduct, all powered by the sun.
Sources
- Singh, Wei, Tang, Xu, Ma & Guo, ‘Additive-free and brine-discharge-free solar-thermal desalination with simultaneous complete mineral mining from ocean water,’ Light: Science & Applications (2026), DOI 10.1038/s41377-026-02315-4
- ‘Rapid lithium extraction via solar-thermal interfacial evaporation with zero liquid discharge,’ Journal of Materials Chemistry A (2026), DOI 10.1039/D5TA08968A
- University of Rochester: New method turns ocean water into drinking water, without waste
- ScienceDaily: New solar desalination breakthrough makes fresh water without toxic brine
- Anthropocene Magazine: A solar-powered system that extracts freshwater and lithium from the sea
Image: sunlit ocean water - a representative photo of the sea this method turns into fresh water, not the actual laboratory device (via Unsplash, released under CC0 / public domain).
Curated by Jerry Cards - jerrycards.com. We research the week’s most hopeful tech, science, and health stories so you don’t have to. More at jerrycards.com/news.