Coal product used to create green clean water

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Compressed blocks of pulverized coal can be used as the basis of sunlight-powered off-grid water purification. The technology is already being progressed by commercial partners toward pilot-scale production of drinking water.

Dark-colored materials that strongly soak up sunlight to drive seawater desalination are a long-standing research interest of KAUST's Andrea Fratalocchi. While reading about the economic challenges of ending coal’s use for power generation, Fratalocchi was struck by a novel possible use for coal. “The two ideas clicked together: why don’t we use coal for a new economy in water desalination?” Fratalocchi recalls.

Fratalocchi and his team began to explore blocks of carbonized compressed powder (CCP), a microporous material produced by forcing powdered coal together under pressure. To assist water flow into and through the CCP, the team incorporated cotton fibers through the material.

The team placed a block of this material over a saltwater-filled container so that the cotton fibers touched the water. When the CCP was warmed by sunlight, water was drawn up through the device and evaporated from its hot surface. A condenser over the device captured the freshwater. The salt left behind in the CCP can be washed off with seawater.

“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, who worked on it as a postdoc in Fratalocchi’s lab. “The device produced fresh water for around one-third the cost of current state-of-the-art solar desalination technologies,”  she adds.

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