Desalination membranes decorated with proteins can alleviate gypsum scaling

There are more than 21,000 desalination plants around the world, according to statistics from the European Union, and those plants pump out about 99 million m³of fresh water every day. Some regions heavily rely on the technology to deliver drinking water, but the reverse osmosis process used to produce that water is far from straightforward. The buildup of mineral scaling in the membranes used in the process reduces their efficiency and lifespan. Now, scientists have shown that adding proteins to the membrane significantly reduces gypsum scaling (ACS Environ. Au 2024, DOI: 10.1021/acsenvironau.4c00057).

In previous work led by Tiezheng Tong, an environmental scientist at Arizona State University, the research team learned that free-floating proteins within water decreases mineral scaling. The group wondered if the effect could be amplified.

That’s why the researchers constructed membranes bedecked in different proteins (bovine serum albumin (BSA), casein, lactalbumin, lysozyme, and protamine). They then tested how well each membrane maintains its capacity to desalinate a controlled composition of gypsum-saturated saline water by measuring the average normalized water flux for 500 min.

The control membrane, which had no proteins added to its surface, was left with just 58% of its water flux capacity at the end of the experiment. The others, excluding protamine, fared better. The casein-coated membrane came out on top, maintaining 93% of its water flux; the BSA-coated membrane was second, at 90%.

“What makes me most proud about these findings is that they’re naturally occurring proteins,” Tong says. He explains that the alternative approach is to make a scaling-resistant membrane with chemicals, which are more expensive and potentially toxic. He hopes that adding these proteins to the membranes will mean that the new technique should not be too difficult to roll out at the desalination plant level.

Although this latest study shows that gypsum scaling can be managed, further experiments are required to see if the method holds true for other forms of mineral scaling. In addition, the study measured gypsum scaling only in the short term. “I have to be very honest and say we don’t know if it works in the long term,” Tong says. “That’s what my students will try to understand in the future.”