Desalinating seawater without brine. A new energy-efficient method

A modern device developed by scientists from the University of Rochester in the United States uses renewable energy to transform seawater into drinking water. The new desalination method eliminates the problem of producing toxic brine, does not require chemical additives for water pre-treatment, and enables lithium extraction.

Ocean water is dirty

The main problem with traditional seawater desalination methods is their carbon footprint – the process is highly energy-intensive, and in many countries the energy used for it still comes from fossil fuels. Although desalination plants powered by photovoltaic systems have already been developed, their operation is still far from ideal.

As Prof. Guo from the Institute of Optics at the University of Rochester explains, most existing photovoltaic-based desalination methods assume that seawater consists only of water and sodium chloride. During evaporation, the salt crystallizes, and its porous crystals were expected to be easily removable from PV panels. In practice, however, oceans also contain magnesium and calcium compounds, which crystallize as well, forming a crust and hindering water flow through the system.

A new desalination method without toxic brine

The authors of an article published on May 27 this year in the journal Light: Science & Applications describe an innovative approach developed by a research team led by Prof. Guo. The breakthrough technology uses black metal solar panels etched with femtosecond lasers, whose surface perfectly absorbs light and effectively removes moisture.

A thin layer of seawater is spread across the panel, which absorbs nearly all solar radiation, distills the water, and deposits residual salts and minerals on the untreated, passive sides of the panel, eliminating the problem of clogging.

Prof. Guo explains that the method he invented uses the so-called coffee-ring effect: If you spill coffee on a surface, the water eventually evaporates, leaving a ring along the outer edge made up of concentrated coffee particles. We use the same principle to move salts into the passive zone.

Producing fresh drinking water with this innovative method does not generate brine, which must otherwise be disposed of in traditional desalination plants. The only waste product is salt in solid form, which can be easily collected from the panels.

The enormous potential of desalination

According to scientists from the University of Rochester, the super-wicking black metal panels could also be used for lithium extraction – a metal that is crucial for the development of batteries and renewable energy technologies, and whose mining from deep underground poses environmental risks. The deposition of hydrogen titanate nanoparticles in tiny grooves on the panel surface makes it possible to isolate lithium from other salts and minerals. Initial tests using water from Great Salt Lake have already been conducted, and researchers managed to extract around 50 percent of the lithium from the remaining salts after the process.

The new desalination method uses solar and thermal energy, is self-operating, and does not require any chemical additives. Scientists emphasize that the system tracks the movement of the sun and operates continuously for a week. Most importantly, it functions in real-world polluted seawater conditions, enabling nearly 100-percent salt extraction.