Approximately 97% of the Earth's water is found in the oceans, but due to salts and other contaminants, such as boron, it requires energy-intensive processing to make it safe to drink.
Seawater has boron levels that are twice the World Health Organization's lowest limit for safe drinking water, and up to 12 times the tolerance for agricultural plants, as a press release shared by TechXplore detailed
The removal of this material usually requires an extra step in the treatment process, as well as expensive chemicals to extract it, but there may be a more sustainable solution.
Water desalination plants primarily use reverse osmosis — pressurizing water to pass through a membrane — to filter out salt and other contaminants, and it's one of the more energy-efficient options available.
Now, new research from the University of Michigan and Rice University offers a cleaner, more efficient method, which could save the world billions.
"Most reverse osmosis membranes don't remove very much boron, so desalination plants typically have to do some post treatment to get rid of the boron, which can be expensive," said Jovan Kamcev, U-M assistant professor and co-corresponding author of the study.
"We developed a new technology that's fairly scalable and can remove boron in an energy-efficient way compared to some of the conventional technologies."
Boron is one of seven essential trace elements in nature, and is beneficial to the growth and development of life on this planet in small doses. Excessive amounts, however, can be toxic to crops and induce diseases in humans and animals.
Since boron exists in seawater as electrically neutral boric acid, it passes through the membranes used in reverse osmosis. As a workaround, desalination plants usually add a base to their treated water, causing the boric acid to become negatively charged, so it can be captured when processed again.
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"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 and co-first author of the study.
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Global desalination capacity was 95 million cubic meters per day back in 2019, as the press release explained, and this new process could save around $6.9 billion annually.
In addition to seawater, around 30% of water in the U.S. stems from underground aquifers, but it's too salty for human use without processing. If we had efficient systems in place to help process this reserve, it could satisfy about 800 years of water use, according to a U.S. Geological Survey report.
This novel carbon cloth electrode process is not only cost-efficient, but it's adaptable to a variety of contaminants, which offers flexibility and scalability in the water treatment sector.
"Our study presents a versatile platform that leverages pH changes that could transform other contaminants, such as arsenic, into easily removable forms," according to Menachem Elimelech, a professor at Rice University and co-corresponding author of the study.
"Additionally, the functional groups on the electrode can be adjusted to specifically bind with different contaminants, facilitating energy-efficient water treatment," Elimelech said.
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