Arid countries with lack of access to freshwater have for decades relied on getting freshwater by separating salt from seawater. But modern desalination technologies are unaffordable, and they consume large amounts of chemicals and energy.
Researchers have now found a way to make a dent in that chemical and energy use. With the help of new carbon cloth electrodes, they report that they can efficiently remove the common contaminant boron from seawater. This eliminates the need for additional post-desalination treatment today’s plants require to get rid of the boron, which add cost and require chemicals.
“Our device reduces the chemical and energy demands of seawater desalination, significantly enhancing environmental sustainability and cutting costs by up to 15 percent, or around 20 cents per cubic meter of treated water,” said Weiyi Pan, a postdoctoral researcher at Rice University, in a press release.
The technique could save large desalination plants millions of dollars a year. Pan and colleagues from Rice University and the University of Michigan reported their new technology in the journal Nature Energy.
The expense of modern desalination plants has relegated them mostly to wealthy Middle Eastern countries such as Saudi Arabia and the UAE. These plants mainly rely on a technology called reverse osmosis, which involves filtering out salt from seawater using membranes.
But reverse osmosis membranes do not remove boron, a drinking water contaminant that is present in seawater. So desalination plants typically add negatively charged chemicals called bases to convert the boron into a removable form. Then they add acids to neutralize the charge. The boron has to be removed via an additional reverse osmosis step.
Removing trace contaminants from water remains a crucial challenge, the Achilles heel, of water treatment, the researchers write. To overcome this challenge, they made porous carbon cloth electrodes with oxygen-containing structures embedded in the pores. These structures selectively bind with boron and lets other ions through.
Instead of adding a negatively charged chemical, the team split water between two electrodes, which created positive hydrogen ions and negative hydroxide ions. The negative hydroxide attaches to boron, giving it a negative charge. The oxygen-based capture sites in the positive electrode efficiently capture the negatively-charged boron. Finally, the hydrogen and hydroxide ions recombine to give boron-free water.
Source: Pan, W., et al. A highly selective and energy-efficient approach to boron removal overcomes the Achilles heel of seawater desalination. Nature Water, 2025.
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