The Daily Populous Thursday December 5th, 2024 morning edition
Authored by unisa.edu.au and submitted by ahothabeth

A novel approach to make seawater evaporate faster than freshwater has been hailed as a significant breakthrough in desalination technology that will benefit billions of people worldwide.

Up to 36% of the world’s eight billion people currently suffer from severe freshwater shortages for at least four months of the year, and this could potentially increase to 75% by 2050, threatening the survival of humans.

Seawater desalination is one of the most effective strategies to alleviate the impending scarcity, but existing processes consume massive amounts of energy, leaving a large carbon footprint.

Researchers from the University of South Australia (UniSA) have already demonstrated the potential of interfacial solar-powered evaporation as an energy-efficient, sustainable alternative to current desalination methods, but they are still limited by a lower evaporation rate for seawater compared to pure water due to the negative effect of salt ions on water evaporation.

UniSA materials science researcher Professor Haolan Xu has now collaborated with researchers from China on a project to develop a simple yet effective strategy to reverse this limitation.

By introducing inexpensive and common clay minerals into a floating photothermal hydrogel evaporator, the team achieved seawater evaporation rates that were 18.8% higher than pure water. This is a significant breakthrough since previous studies all found seawater evaporation rates were around 8% lower than pure water.

“The key to this breakthrough lies in the ion exchange process at the air-water interface,” Prof Xu says.

“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.”

Considering the global desalination market – which numbers around 17,000 operational plants worldwide – even small declines 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 systems, will provide additional access to massive amounts of clean water, benefitting billions of people worldwide,” Prof Xu says.

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 pure water evaporation and apply them into practical seawater desalination.

The findings have been published in the journal Advanced Materials.

“Making Interfacial Solar Evaporation of Seawater Faster than Freshwater” is authored by researchers from the University of South Australia, Shenzhen Institute of Advanced Technology, Jinan University, Tianjin University, University of New South Wales, University of Adelaide, Shanghai Jiao Tong University and Nanjing Forestry University. DOI: 10.1002/adma.202414045

The mineral materials used in the process included halloysite nanotubes (HNTs), bentonite (BN), zeolite (ZL), and montmorillonite (MN) in combination with carbon nanotubes (CNTs) and sodium alginate (SA) to form a photothermal hydrogel.

Media contact: Candy Gibson M: +61 434 605 142 E: candy.gibson@unisa.edu.au

Research contacts: Professor Haolan Xu E: haolan.xu@unisa.edu.au; Dr Gary Owens

Submissive-whims on December 4th, 2024 at 19:02 UTC »

The technology here is apparently somewhat similar to a catalyst in that it lowers the energy required for some reaction. Think of how we historically made fertilizer by using iron as a catalyst for hydrogen and nitrogen to make ammonia. In this case the claim is that doping a “photothermal hydrogel evaporator” with certain relatively common minerals it’s possible to pull out some of the saltiness from seawater to reduce the amount of energy required to evaporate out fresh water. Apparently the catalyst is reusable.

To those that say this tech will be squashed due to not making financial sense, I say nonsense. It’s a relatively cheap but potentially scalable method to bring freshwater to areas that normally don’t have enough. That opens the door for industrial plants to operate relatively cheaply in proximity to salt water for cities or towns to develop around other important resources that we typically can’t exploit due to the logistics of supporting a town. Rather than profiting off of water there’s enormous profit to be made from the consequences of cheap water. It’s potentially feasible that sufficiently large plants near the ocean could supply mega canals or pipelines to interior cities. Libya for instance does something similar with a pipeline from interior freshwater aquifers to their more costal cities.

As far as limitations go the method this article talks about is for solar evaporation. Costal zones with relatively consistent cloud cover are going to get less benefit. I’m interested to see if the Middle Eastern OPEC nations choose to invest in this tech in an attempt to cultivate some non-desert biomes. Could be useful for them in a world dominated by renewables.

IandouglasB on December 4th, 2024 at 18:44 UTC »

Not if corporations can't make billions from it. If they can't this technology will disappear just like so many others...

GreedAndPride on December 4th, 2024 at 18:35 UTC »

Don’t tell Nestle about this