For water-stressed coastal regions, the sea can be a vital lifeline; a single desalination plant can draw from it to provide cities with up to a million litres of fresh water a day. However, desalination also generates large amounts of mineral-rich brine which often ends up back in the sea.
Extracting minerals from brine would both make it more environmentally-friendly and recover valuable minerals like magnesium and calcium, but it’s easier said than done, according to Yan Liu and Jiajian Gao, respectively Principal and Senior Scientists at the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2).
“Traditional mineral extraction methods often involve adding alkaline chemicals like lime or ammonia, but those can be costly to transport to remote locations, and may generate harmful byproducts,” Liu and Gao explained.
In search of better alternatives, Liu, Gao and A*STAR ISCE2 colleagues proposed a novel ‘one-pot’ electrochemical system that would simultaneously extract minerals from brine, and carbon dioxide (CO2) from the air. By harnessing a chemical process known as the oxygen reduction reaction (ORR), the system produces hydroxide ions from atmospheric oxygen. These alkaline ions then react with brine and CO2, locking magnesium, calcium and CO2 into useful solid products such as calcium carbonate and magnesium carbonate.
“Using green electricity to create green alkaline, our system uses desalination brine to effectively combat climate change while recovering essential minerals for circular economy,” said Liu and Gao.
The team put their concept to the test by building a prototype electrochemical reactor, with encouraging results: using a 60 mA current (similar to a desk lamp) over eight hours, the reactor extracted up to 28 percent of magnesium and 64 percent of calcium from a 100 mL sample of brine. What’s more, nearly 40 percent of the recovered minerals were in carbonate forms.
“This was a big win because it proved that the system wasn’t just cleaning up the brine—it was also capturing atmospheric CO2,” said Liu and Gao. “An added surprise was its energy efficiency: it used 30 percent less energy than traditional methods of mineral extraction. All these features make the system a cost-effective, practical and environmentally-friendly solution.”
Liu and Gao hope that their system also inspires more integrated green approaches to resource recovery. “This could lead to new technologies that combine brine management with environmental solutions, making processes like desalination not only sustainable but profitable,” they added.
For now, the team is looking into commercialising their system and are collaborating with Pan-United Concrete Pte Ltd to explore potential applications for its recovered minerals. They are also working to improve the system’s reactor designs and catalysts, aiming to boost the system’s efficiency and cost-effectiveness.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2).
