Dec. 4 () –
A new method for seawater to evaporate faster than fresh water represents a significant advance in desalination technology that can benefit billions of people.
Up to 36% of the world’s 8 billion people currently suffer from severe shortage of fresh water for at least four months of the year, and this figure could increase to 75% in 2050.
Seawater desalination is one of the most effective strategies to alleviate the impending shortage, But existing processes consume enormous amounts of energy and leave a large carbon footprint.
Researchers at the University of South Australia (UniSA) have already demonstrated the potential of solar-powered interfacial evaporation as a sustainable and energy-efficient alternative to current desalination methods, but are still limited by a lower evaporation rate of the sea water compared to pure water due to the negative effect of salt ions on water evaporation.
Professor Haolan Xu, a researcher at the University of Saxony in the field of materials, has collaborated with researchers in China on a project to develop a simple but effective strategy to reverse this limitation. These new results have been published in the journal Advanced Materials.
By introducing inexpensive and common clay minerals into a floating photothermal hydrogel evaporator, the team achieved seawater evaporation rates 18.8% higher than pure water. This is a significant development, as previous studies have shown that seawater evaporation rates were approximately 8% lower than pure water.
The mineral materials used in the process included halloysite, bentonite, zeolite and montmorillonite nanotubes in combination with carbon nanotubes and sodium alginate to form a photothermal hydrogel.
“The key to this advance lies in the ion exchange process at the air-water interface,” says Professor Xu in a statement.
“The minerals selectively enrich seawater magnesium and calcium ions on evaporation surfaces, which increases the evaporation rate of seawater. This ion exchange process occurs spontaneously during solar evaporation, making it very convenient and cost-effective.“.
Considering the global desalination market, which has some 17,000 operating plants worldwide, even small decreases in desalination performance can result in the loss of tens of millions of tons of clean water.
“This new strategy, which could be easily integrated into existing evaporation-based desalination systemswill provide additional access to massive amounts of clean water, which will benefit billions of people around the world,” says Professor Xu.
The researchers say the hydrogel evaporator maintained its performance even after months of immersion in seawater.
The next steps will involve exploring more strategies that can make seawater evaporation faster than pure water evaporation and applying them in practical seawater desalination.
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