Desalination tech could solve water shortage crisis

Researchers from Monash University have developed a desalination technology that has the potential to deliver clean, potable water to thousands of communities, simply by using photothermal materials and the power of the sun. The solar steam generation system produces continuous clean water from salty ocean water with almost 100% salt removal. The technology is a promising solution to water shortages in regional areas lacking access to grid electricity.

Led by Professor Xiwang Zhang from Monash University’s Department of Chemical Engineering, the research team’s novel design allows precision control of salt crystallisation at the edge of an evaporation disc, with the ability to harvest the salts. The feasibility and durability of the design have been validated using seawater from Lacepede Bay in South Australia, with findings published in the journal Energy & Environmental Science.

The evaporation disc uses super-hydrophilic filter paper, with a layer of carbon nanotubes for light absorption. A cotton thread (1 mm diameter) acts as the water transport channel, pumping saline water to the disc. Saline water is carried up by the cotton thread from the bulk solution to the centre of the evaporation disc where the filter paper traps the pure water and pushes the remaining salt to the edges of the disc.

Light absorbance was measured to 94% across the entire solar spectrum. The disc exhibited a rapid temperature increase when exposed to light in both dry and wet states, rising from 25 to 50°C and 17.5 to 30°C, respectively, within one minute.

“Utilising solar energy for water treatment has been widely considered as one of the sustainable solutions towards addressing the scarcity of clean water in some communities, without sacrificing our environment or resources,” Prof Zhang said.

“Despite the significant progress achieved in material development, the evaporation process has been impeded by the concentration of salt on the surface, which affects the quality of water produced,” he explained.

The technology has potential in other fields such as industry wastewater zero liquid discharge, sludge dewatering, mining tailings management and resource recovery. Future studies will look to extend the technology to these applications.

“Our study results advance one step further towards the practical application of solar steam generation technology, demonstrating great potential in seawater desalination, resource recovery from wastewater and zero liquid discharge,” Prof Zhang said.

“We hope this research can be the starting point for further research in energy-passive ways of providing clean and safe water to millions of people, illuminating the environmental impact of waste and recovering resource from waste.”

Image credit: © Monash University