By John — Desalination News
Researchers at Saudi Arabia’s King Abdullah University of Science and Technology (KAUST) have developed an ultrathin, water-repellent membrane that can desalinate seawater and even highly concentrated industrial brines without the intense pressure that reverse osmosis requires or the heating that conventional membrane distillation depends on, in a technique the university describes as a potential route to markedly more sustainable desalination.
The membrane, described in a paper in Nature Communications led by KAUST professor Noreddine Ghaffour, is a polymeric film less than a micrometer thick, laid over a porous support. Its defining feature is a surface riddled with sub-nanometer pores that is also superhydrophobic, meaning it repels liquid water so completely that salty feed water cannot flood or clog its pores even as vapor passes through them. Feed water held at around 25 degrees Celsius sits on one side of the membrane while slightly cooler water, about 20 degrees, sits on the other; the small temperature difference between the two is enough to drive water vapor across the membrane, where it condenses into fresh water on the cooler side while dissolved salts and other contaminants are left behind.
That mechanism places the KAUST membrane within the established field of membrane distillation, a thermal desalination approach long valued for handling very salty or chemically difficult water but hampered by its reliance on meaningfully heated feed water, which has kept it from competing with reverse osmosis on energy use. The KAUST team’s approach instead runs at close to room temperature and atmospheric pressure, which the university says translates into substantially lower energy demand than conventional thermal or pressure-driven methods, though the published material discloses no specific energy-consumption or water-flux figures. The membrane is also reported to achieve very high salt rejection, including a complete barrier to boron, a contaminant notoriously difficult for conventional reverse osmosis membranes to filter out completely, and to resist degradation from the chlorine-based oxidants commonly used to control biological fouling in desalination systems. The approach joins a broader wave of advanced-membrane research the desalination industry has pursued this year, including a zwitterionic membrane designed to pair water purification with clean-energy generation, though the KAUST design targets a different part of the cost equation by removing pressure and heat from the process entirely.
Beyond conventional seawater desalination, the KAUST team points to a particular opportunity in treating brine and produced water, the concentrated salty waste streams left over from existing desalination plants and oil and gas operations, which are typically too saline for standard reverse osmosis to process economically. A membrane that can handle those difficult, highly concentrated streams at ambient conditions could help plants extract more usable water from what is currently discarded as waste, while easing the cost and environmental burden of brine disposal that has become an increasingly prominent concern as plants expand. The technology is also being pitched for small-scale, remote deployments, where skipping high-pressure pumping equipment or substantial heating infrastructure could simplify installation in areas without a robust power supply.
The university says a pilot unit is currently being evaluated on KAUST’s campus, with the research team now focused on testing the membrane’s durability and scalability under a range of operating conditions before any move toward commercial deployment; no timeline has been disclosed, and the work has not yet been linked to a specific industrial partner or pilot plant project. Ghaffour said in comments accompanying the research that water and energy challenges are inseparable for Saudi Arabia, and that the work shows it is possible to desalinate highly concentrated brines using far less energy than traditional approaches. If the membrane performs as described at larger scale, it would add a genuinely low-energy option to a desalination toolkit still dominated by reverse osmosis and conventional thermal plants, particularly for the brine streams and remote applications that existing technologies handle least efficiently.
(Source: KAUST Discovery, Nature Communications)