Reviewed by Lexie CornerJan 21 2025
Engineers from the University of Michigan and Rice University have developed a method to replace costly chemical treatments in desalination plants with carbon cloth electrodes that remove boron from seawater. The study, published in Nature Water, represents a step forward in making seawater desalination more efficient and suitable for safe drinking water.
Jovan Kamcev, an assistant professor of chemical engineering and macromolecular science and engineering at U-M, places a filter membrane between two electrodes, which measures how well the membrane conducts electricity. This helps his team predict how well it can purify water. Image Credit: Marcin Szczepanski, Michigan Engineering
Boron, a naturally occurring component of seawater, becomes a pollutant when present in drinking water at levels exceeding safety limits. Seawater boron levels are roughly twice the World Health Organization's maximum allowable limits for drinking water and five to twelve times the tolerance of many crops.
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; 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.
Jovan Kamcev, Study Co-Corresponding Author and Assistant Professor, Chemical Engineering and Macromolecular Science and Engineering, University of Michigan
In seawater, boron exists primarily as electrically neutral boric acid, which can pass through reverse osmosis membranes designed to repel charged particles (ions). To address this, desalination plants traditionally add a base to convert boric acid into negatively charged boron species, which are removed through an additional reverse osmosis step. The water is then neutralized with acid. This multi-step chemical treatment is costly.
Our device reduces the chemical and energy demands of seawater desalination, significantly enhancing environmental sustainability and cutting costs by up to 15 %, or around 20 cents per cubic meter of treated water.
Weiyi Pan, Study Co-First Author and Postdoctoral Researcher, Rice University
The study highlights the potential of new carbon cloth electrodes to reduce costs. With a global desalination capacity of 95 million cubic meters per day in 2019, these electrodes could save an estimated $6.9 billion annually. Large facilities, such as the Claude "Bud" Lewis Carlsbad Desalination Plant in San Diego, could result in significant savings, making desalinated seawater a more accessible source of drinking water. This could help mitigate the global water shortage, with freshwater supplies projected to meet only 40 % of demand by 2030, according to a 2023 report from the Global Commission on the Economics of Water.
The new electrodes remove boron by trapping it within pores lined with oxygen-containing structures. These structures selectively bind boron while allowing other ions in seawater to pass through, increasing the efficiency of boron capture.
For these structures to function, boron must carry a negative charge. Rather than adding a chemical base, the system generates the charge by splitting water between two electrodes, producing positive hydrogen ions and negative hydroxide ions. The hydroxide ions react with boron, giving it a negative charge that adheres to the capture sites in the pores of the positive electrode. This approach eliminates the need for an additional reverse osmosis step, reducing energy consumption. The hydrogen and hydroxide ions then recombine, yielding neutral, boron-free water.
Our study presents a versatile platform that leverages pH changes that could transform other contaminants, such as arsenic, into easily removable forms.
Menachem Elimelech, Study Co-Corresponding Author and Nancy and Clint Carlson Professor, Civil and Environmental Engineering and Chemical and Biomolecular Engineering, Rice University
“Additionally, the functional groups on the electrode can be adjusted to specifically bind with different contaminants, facilitating energy-efficient water treatment,” added Elimelech.
The electrodes were examined at Michigan’s Center for Materials Characterization.
Journal Reference:
Pan, W., et al. (2025) A highly selective and energy-efficient approach to boron removal overcomes the Achilles heel of seawater desalination. Nature Water. doi.org/10.1038/s44221-024-00362-y