Treating waste brine using a self-cleaning crystallizer that runs on solar power could be an eco-friendly and efficient way to make seawater desalination more sustainable.

In desert regions, seawater desalination provides essential freshwater for drinking and agriculture. A major problem is that the process generates vast quantities of concentrated brine that is often released into nearby lakes and rivers or back into the sea, harming vegetation and marine life. “With tightening environmental regulations and increasing public awareness, there is pressure to treat brine with zero liquid discharge,” says Chenlin Zhang, a Ph.D. student in KAUST. This means extracting every last drop of water while leaving behind solid mineral crystals that can be salvaged for other uses.

Crystallization currently requires either expensive corrosion-resistant containers and large amounts of energy to boil the brine or large areas of land as dedicated evaporation ponds. Solar crystallizers that use photothermal materials to convert sunlight into heat are gaining popularity but have limited performance because they accumulate salt crystals, which reduce light absorption at the surface.

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Image: KAUST researchers have developed a solar-powered crystallizer that can be used to treat brine produced by water desalination plants in an eco-friendly way.
© 2021 Nature; Zhang et al.