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Photocatalysis-Based Water Purifier Uses Sunlight to Break Down Impurities

How photocatalysis works

Cleaning water effectively so it becomes potable is an important issue in poor countries nowadays. Using solar power, a team from the Hong Kong Polytechnic University led by Xuming Zhang, built a water purifier that improves the technology with a novel approach.

They use two distinct methods: microfluidics (transporting water through tiny channels) and photocatalysis (using light to break down water impurities). These two techniques form a new science called optofluidics.

“These two technologies have been developed in parallel but there have been few efforts to employ the natural synergy between them,” says Xuming Zhang. “Our results showed a dramatic improvement in the efficiency of the photocatalyst.”

The new water purifier is made as a planar microfluidic reactor (microreactor). The microreactor is a rectangular-shaped chamber made of two titanium dioxide-coated glass plates. The titanium dioxide emits electrons when exposed to sunlight. These electrons break down the water contaminants into harmless substances (this process is the photocatalysis).

For the moment, the two glasses have a very small gap between them, but the current prototype is only a proof of concept. Zhang’s plans are big, though. He wants to upscale the concept so it is able to filter 1,000 liters per hour, with the possibility of having multiple parallel devices installed in industrial water treatment plants.

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