The sun-powered sponge that purifies wastewater

Every day, an estimated 80% of the world’s wastewater flows untreated into the environment, carrying a toxic cocktail of pollutants with it. The contaminants can be organic compounds such as dyes originating from industries including textiles, or drug residues from pharmaceutical production and sewage. These pollutants pose serious risks to our health and throw our ecosystems off balance. 

Now, researchers at Khalifa University have developed a cleverly designed water treatment technology that uses sunlight to quickly capture and destroy such organic pollutants. “The new material helps advance wastewater treatment technologies toward the more practical, low-cost and environmentally friendly solutions needed for global clean-water initiatives,” says study lead Xuan Li. The postdoctoral fellow at KU’s Research and Innovation Center on CO₂ and Hydrogen worked with Lianxi Zheng, professor of mechanical and nuclear engineering, and others at the university. 

Existing water treatment methods either trap pollutants, requiring a separate and often messy clean-up process, or break them down using sunlight in a process too slow for large-scale use. By combining the benefits of both these strategies, the team came up with a new photocatalyst made of nano-sized titanium dioxide (TiO₂) and molybdenum disulfide (MoS₂), a material known for its strong ability to trap pollutants. With a new fabrication technique, they grew tiny flakes of MoS₂ on the edges of nano-sized TiO₂ tiles. 

“The photocatalyst is like a two-in-one cleaning sponge,” Li explains. The MoS₂ flakes quickly soak up pollutants in the same way that a sponge absorbs spills. The TiO₂ tiles then use sunlight to slowly break down the pollutants into harmless substances. “Together, it removes and destroys pollutants efficiently, keeping the water clean without leaving harmful residues behind,” she says. 

In tests with water mixed with common dyes, pharmaceuticals and phenols—which are pollutants often discharged into wastewater from manufacturing—the new catalysts cleared up to 90% of contaminants in just 30 minutes.  

Unlike older, randomly mixed materials that sometimes struggled to do both jobs at once, the new material’s unique design separates the trapping and destroying functions. “The unique structure ensures both functions remain effective without interfering with each other. It also helps the photocatalyst maintain excellent performance over time,” Li says. 

“The new material helps advance wastewater treatment technologies towards more practical, low-cost and environmentally friendly solutions needed for global clean water initiatives.”  

Xuan Li 

Experts not involved in the study suggest that future work should measure the technology against the performance of existing solutions and assess the costs of scaling it to plant-level operation. 

With further testing, Li is hopeful that the technology could be integrated into wastewater treatment plants or adapted into portable purification systems for remote areas and emergency situations. “A critical next step is to test the catalyst with real wastewater, which often contains complex mixtures of pollutants,” she says. 

Reference

Li, X.; Li, B.; Ji, D.; Guan, Q.; Thirumalraj, B.; Palmisano, G. and Zheng, L., A highly efficient bifunctional Z-scheme photocatalyst with spatially-separated and synergistically-enhanced adsorption and photodegradation. Appl. Catal. B: Environ. Energy, 362, 124758, 2025. | Article