U-M researchers develop cheaper, easier method to make seawater safe to drink

Engineers at the University of Michigan (U-M) and Houston-based Rice University have developed technology that makes it easier and cheaper to render seawater safe to drink.

The technology efficiently removes boron, a natural component of seawater that exists as boric acid, from water without using costly chemicals. Boron becomes a toxic contaminant in drinking water if it gets past conventional filters for removing salts. The technology has the potential to make seawater a more affordable option for drinking water – which could positively impact the global water crisis. 

"I think getting clean water, and access to clean water, has been a big problem for a long time that's not going to be solved soon," says Jovan Kamcev, U-M assistant professor of chemical engineering and macromolecular science and engineering. "But we just keep making these types of steps and leaps, and one day we'll have a good solution to the problem." 

The new technology, which uses carbon cloth electrodes to remove boron from seawater, is described in a new study in the journal Nature Water. Kamcev is a co-corresponding author of the study. To explain why he's excited about the results, he points to other researchers' estimates that 70% of the global population will suffer some water scarcity at some point in the year. 

"Is the problem that we don't have enough water at all, or just that we don't have enough clean water?" Kamcev says. "The answer is we have plenty of water located in the sea."

Kamcev explains that the current dominant technology used for water purification involves reverse osmosis membranes. While the membranes are great for separating salt and water, they're not very good for contaminants that are really small. Boron molecules are much smaller than salt molecules, and they're electrically neutral. 

Desalination plants usually add a base to their treated water, which causes boric acid to become negatively charged and larger. Another stage of reverse osmosis removes the newly charged boron, and then acid is added to bring the water's pH balance back to neutral. 

"There's a lot of expensive post-treatment that needs to be done to get the boron out, whereas the salt is usually taken care of in that first pass," Kamcev says. "That's what motivated us to try to develop a better way to get rid of this boron, because it is present everywhere."

The new technology has been shown to cut costs by up to 15%, or roughly 20 cents per cubic meter of treated water. Large desalination plants could save millions of dollars yearly. Globally, the new membranes could save around $6.9 billion annually. 

Kamcev says the next step is securing an industrial partner to examine the technology's scalability. 

"Some of the electrodes that we were using for this technology are basically carbon cloth, which are very inexpensive. All of the chemical modifications were very simple, inexpensive methods," he says. "We were always keeping in mind that this would have to be scaled up, and so I don't see any constraints going forward."

Jaishree Drepaul is a writer and editor based in Ann Arbor. She can be reached at jaishreeedit@gmail.com. 

Photo by Marcin Szczepanski, Michigan Engineering.