Researchers Develop Greener Desalination Coating


A new polyelectrolyte coating developed by researchers from the King Abdullah University of Science and Technology has been reported to enable clean seawater desalination systems without harmful chemicals.

The removable, nontoxic coating is being reported by KAUST to provide a safer and more efficient alternative to harmful chemicals used to clean reverse osmosis systems for seawater desalination. The process uses pressure to filter seawater through a semipermeable membrane to produce fresh drinking water and can be hindered by the growth of bacteria and other microorganisms on the membrane surface.

“This biofilm creates a layer that does not allow water to pass as easily,” said Maria Fernanda Nava-Ocampo, a PhD student under the supervision of Johannes Vrouwenvelder. “One of the biggest problems of all the current methods to control biofouling is that they do not completely remove the biofilm from the membrane system, resulting in permanent fouling. This causes elevated energy consumption and disposal of control chemicals into the sea.”

According to KAUST, its polyelectrolyte coating avoids the need for toxic linkers to attach to the membrane and can be safely flushed out of the system with brine and increased flow, leaving the membrane surface clear of biofilm.

“The advantage of our coating is that it attaches to the surface by electrostatic interactions, so we don't have to use chemicals,” said Nava-Ocampo. “We also don’t have to pretreat the membrane in order to coat it. The membrane stays in the system and we just pass the coating through the same current flow used for desalination.”

To test the coating, the team of researchers circulated the coating in a membrane fouling simulator—a small device that mimics the conditions in reverse osmosis desalination plants—five times in order to establish layers on the surface of the membrane and add biodegradable nutrients for biofilm growth.

After eight days, the team removed the coating by flushing the system using a high-saline solution for 24 hours and compared the performance of the coated membrane with a non-coated control membrane, finding that the coating remained stable in salty water, making it suitable for seawater desalination.

KAUST adds that, after the cleaning process was completed, liquid flowed through the coated membrane two times higher than its uncoated counterpart.

“This showed that our technique has better cleaning potential,” says Nava-Ocampo. “The next step is making it more efficient and durable at larger scales.”


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