Efforts to address global water scarcity have driven advancements in technologies for water conservation, re-use, and treatment. Among these, desalination of seawater is a well-established method to combat shortages, although it is known for being energy-intensive. In contrast, solar-powered evaporation offers a more energy-efficient alternative. However, the presence of salt in seawater reduces the evaporation rate, with studies indicating seawater evaporates about 8% slower than pure water.

Researchers from the University of South Australia (UniSA), led by Professor Haolan Xu, have developed an innovative approach to overcome this limitation. By incorporating common clay minerals into a floating photothermal hydrogen evaporator, the team achieved seawater evaporation rates 18.8% higher than those for pure water. The materials used in this breakthrough include halloysite nanotubes (HNTs), bentonite (BN), zeolite (ZL), and montmorillonite (MN), combined with carbon nanotubes (CNTs) and sodium alginate (SA) to create a photothermal hydrogel. Impressively, the hydrogen evaporator maintained its performance for months after immersion in seawater.

“The key to this breakthrough lies in the ion exchange process at the air-water interface,” Xu explains. “The minerals selectively enrich magnesium and calcium ions from seawater to the evaporation surfaces, which boosts the evaporation rate of seawater. This ion-exchange process occurs spontaneously during solar evaporation, making it highly convenient and cost-effective.”

The collaborative effort between UniSA and researchers from China highlights the potential of natural mineral materials in enhancing the efficiency of solar desalination processes. This simple and cost-effective strategy represents a significant step forward in sustainable water treatment technologies.