Mangroves, membranes and sunlight: The UAE’s quest for clean water

Under the blazing sun of the United Arab Emirates, coastal mangroves quietly perform a daily miracle: drawing seawater through their roots and filtering out the salt on the surface of their leaves. This natural process has inspired scientists at Khalifa University in their search for sustainable solutions to one of humanity’s most pressing challenges: water scarcity.

“Nature found a way to manage salty water without damaging the environment. We asked ourselves, could we do the same, using nothing more than sunlight,” says TieJun Zhang, who leads the Solar-Water team at the university, together with Faisal Al Marzooqi.

Harnessing free, abundant sunlight is at the heart of a new generation of clean, low-impact technologies. This idea has sparked several collaborative projects between the university and Dubai Electricity and Water Authority (DEWA). The partnership emerged after DEWA approached the university with a challenge: to develop water desalination technologies aligned with the UAE’s Water Security Strategy 2036 and its goal of producing 100% desalinated water using clean energy by 2030. The system needed to be energy-efficient, affordable and most importantly, sustainable.  

“Given DEWA’s global industrial leadership in both industrial scale desalination and solar energy projects, its collaboration and support has been central in our research work,” says Al Marzooqi. 

“Our team is all about creating technologies that are both scientifically innovative and environmentally responsible.” 

TieJun Zhang

From mangrove-mimicking systems to cutting-edge photothermal membranes, KU researchers are collaborating with local companies to create scalable water treatment solutions designed to address big environmental goals.

Mimicking mangroves 

Transforming seawater into freshwater is often touted as the answer to the global water crisis, but traditional methods such as reverse osmosis can be expensive and rely on fossil fuels or electricity-intensive processes. Another big issue is the leftover brine—a salty concentrate that’s hard to dispose of and can threaten marine life.

The team at KU is working on an alternative solution; a mangrove-inspired solar distillation device. Built from a low-cost, corrosion-resistant titanium mesh covered by nanostructured titanium dioxide, the device resembles a cluster of leaves around a central stem. Like mangrove roots, the stem constantly brings up more water, like a sponge, using capillary action. Then, on the artificial leaves, salty water turns into vapor, which condenses as freshwater. Rather than forming brine, the salt crystallizes along the edges of the device during the day—just as in real mangrove leaves—and naturally flakes off at night.

This clever design allows the salt to be passively peeled, collected and even reused. In early tests, the device successfully turned seawater and high-salinity waste into fresh water with no brine discharge. With a photothermal efficiency of around 94%, the device can produce up to 2.2 liters of freshwater per square meter of seawater per day—enough to meet an individual’s daily drinking water needs^1.2.

The researchers are working on scaling up this technology: leaf units can be added or removed based on demand.

“The entire device is fabricated using a simple, one-step process with low-cost, commercially available materials, making it both scalable and efficient for solar-driven water purification,” says research scientist Aikifa Raza.   

Tiny nanoparticles, big clean water impact

The team is also working on another innovation: a solar-driven membrane distillation system. This is a process that uses heat to separate clean water from saltwater, rather than relying on pressure and filtration as reverse osmosis does. It works by heating the salty water to produce water vapor. A special water-repellent, membrane allows only vapor to pass through, blocking liquid water and salt. The vapor is then cooled, turning back into clean water.

Heating the entire volume of water using solar energy, however, is not particularly efficient, as temperature tends to drop rapidly near the membrane surface, reducing the effectiveness of vapor generation. To overcome this challenge, the team has developed a membrane made of PVDF polymer with zirconium nitride nanoparticles. These particles absorb sunlight, vibrate in a special way and give off heat; making the water evaporate faster and more efficiently.

These membranes absorb up to 75% of sunlight—significantly more than unmodified membranes—and are 56% more porous, allowing water vapor to pass through more easily. Thanks to these features, the system can consistently produce clean water while removing approximately 99% of the salt.^3,4.

From lab bench to real-world readiness

What sets these solar desalination breakthroughs apart is simplicity and scalability. Unlike many conventional systems that require specialized infrastructure, these devices are made from common, low-cost materials that are easy to assemble. This keeps both the upfront cost and maintenance requirements low—an essential combination for large-scale adoption.

The team is making progress in automating the system, integrating smart sensors for real-time monitoring and refining deployment models for different environments in preparation for pilot tests in collaboration with UAE-based companies. These real-world trials will assess how the distillation devices perform in real conditions involving strong sunlight, varying salt levels and the day-to-day demands of operational use.

“By working closely with industry partners, we can fine-tune the design, assess long-term durability, and gather valuable data to support scaling and commercialization,” explains Raza.   

If successful, the impact could be far-reaching, supporting off-grid communities in water-scarce regions and reducing greenhouse gas emissions. 

Looking ahead

Beyond seawater desalination, the systems hold potential for treating high-salinity wastewater produced from traditional energy and mining sectors, where conventional treatment methods often fall short.

The same solar membrane distillation technology could also be applied to recycle grey water for use in agriculture and landscaping or be adapted to concentrate solutes in processes involved in food production and mineral recovery.

“Our team is all about creating technologies that are both scientifically innovative and environmentally responsible,” says Zhang.  

Reference

1. Abdelsalam, M.A., Sajjad, M., Raza, A., AlMarzooqi, F., & Zhang, T. Sustainable biomimetic solar distillation with edge crystallization for passive salt collection and zero brine discharge. Nat. Comms., 15(1), 874, 2024. | Article 

2. Sajjad, M., Abdelsalam, M.A., Raza, A., AlMarzooqi, F., & Zhang, T. Capillary pumping-evaporation modeling and experimental characterization of saline water transport for passive solar desalination. Int. J. Heat Mass Transf., 223, 125172 2024. | Article 

3. Li, H., Raza, A., AlMarzooqi, N.A., AlMehrzi, M., Shaheen, A., AlMarzooqi, F., & Zhang, T. Solar-Driven Thin Air Gap Membrane Distillation with a Slippery Condensing Surface. Environ. Sci. Technol., 58(47) 2024. | Article 

4. AlMehrzi, M., Shaheen, A., Ghazal, A., Almarzooqi, N., Raza, A., Zhang, T., & AlMarzooqi, F. Photothermal ZrN composite membranes for solar-driven water distillation. J. Environ. Chem. Eng., 12(5), 2024.  | Article