Clean water is essential for human survival and development, but population growth, urbanization, and industrialization have strained natural freshwater supplies. More than 97% of Earth's water is seawater or brackish water, which is too salty for direct use. Conventional desalination technologies are energy-intensive or costly to maintain, and their reliance on fossil fuels worsens the global energy crisis.

Now, researchers from the Xinjiang Technical Institute of Physics and Chemistry (XTIPC) of the Chinese Academy of Sciences (CAS) have developed an innovative evaporator that can produce clean water efficiently around the clock using both solar energy and electricity. The study was recently published in Separation and Purification Technology.

Led by Prof. Abudukeremu Kadier and Prof. MA Pengcheng, the team created a basalt fabric-based photothermal interfacial PPY-CNTs-PDA@BF evaporator and integrated with an SSM 304 electrothermal layer. This design allows it for all-weather efficient brackish water desalination.

In lab tests under simulated sunlight (1 sun) with 1.5 V electric input, the device achieved an evaporation rate of 4.43 kg m^-2 h^-1. Under real outdoor sunlight with the same voltage, the rate reached 6.37 kg m^-2 h^-1. Thanks to its Janus hydrophilicity gradient structure, the evaporator resisted salt buildup and maintained stable performance for 120 hours straight, with daytime evaporation rates above 2.17 kg m^-2 h^-1.

The purified water meets WHO drinking water standards, with significantly reduced ion concentrations and chemical oxygen demand. The technology could offer a sustainable solution for water-scarce regions worldwide, the researchers noted.

This work was supported by several funding programs, including the Natural Science Foundation of Xinjiang Uygur Autonomous Region, and the National Foreign Young Talents Program-Department of Foreign Expert Services of the Ministry of Science and Technology, China, among other sources.

Illustration of real-world application scheme of the photo-electrothermal interfacial evaporation system with PPY-CNTs-PDA@BF evaporator. (Image by XTIPC)