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Coal to Desalinate Seawater

Whilst coal-fired power plants are soon to be consigned to history, it looks like coal may actually be useful as an eco-friendly component in desalinating seawater.

Researchers at Saudi Arabia’s King Abdullah University of Science and Technology (KAUST), have been experimenting with coal by grinding it into a powder, then compressing it back into a solid. The result is a material more porous than in its original form and is called carbonized compressed powder (CCP).

After creating CCP, the team combined it with natural cotton fibers and then placed a CCP block within a seawater container, with the the block touching the surface of the water. In tests, the team placed the device out in the sun so the black surface of the block would heat up, while the absorbent fibers drew water in from the sides. The water then evaporated when it touched the hot surface of the block, condensing on the inside of a pyramid-like cover. That condensed fresh water was then easily collected.

The salt remained behind within the CCP and was easy to wash off with seawater, so that block is suitable for multiple uses. And, at the end of its useful life, can be disposed of as non-toxic, biodegradable waste. Furthermore, the CCP device has a desalination rate per unit two to three times higher than that of any other solar desalination system. Or, put another way, it's a much cheaper option.

CCP looks like it may be a game-changer in regions where clean drinking water is scarce. That would certainly be good news.

The KAUST team has now partnered with a Dutch company with a view to scaling up and commercializing the technology. The plan is to test the device at a pilot plant in Brazil, where it will be used to desalinate brackish water for drinking and cooking purposes.

“CCP is abundant in nature and low-cost, as well as lightweight, versatile, and highly scalable from a fabrication point of view,” says Marcella Bonifazi, one of the KAUST researchers. “The device produced fresh water for around one-third the cost of current state-of-the-art solar desalination technologies.”

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