Spinning CDs to clean sewage water
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60 Minutes
WASHINGTON:Wondering
what to do with your obsolete audio CDs? Researchers have come up with a
practical application: they can be used to break down sewage.
"Optical disks are cheap, readily available, and very commonly used," said Din Ping Tsai, a physicist at National Taiwan University. Close to 20 billion disks are already manufactured annually, the researchers noted.
Tsai and his colleagues used the large surface area of optical disks as a platform to grow tiny, upright zinc oxide nanorods about a thousandth the width of a human hair. Zinc oxide is an inexpensive semiconductor that can function as a photocatalyst, breaking apart organic molecules like the pollutants in sewage when illuminated with UV light.
As the disks are durable and able to spin quickly, contaminated water that drips onto the device spreads out in a thin film that light can easily pass through, speeding up the degradation. The team's complete water treatment device is approximately one cubic foot in volume. The device also consists of a UV light source and a system that recirculates the water to further break down the pollutants.
The team tested the reactor with a solution of methyl orange dye. After treating a half-litre solution for 60 minutes, they found that over 95% of the contaminants had been broken down.
"Optical disks are cheap, readily available, and very commonly used," said Din Ping Tsai, a physicist at National Taiwan University. Close to 20 billion disks are already manufactured annually, the researchers noted.
Tsai and his colleagues used the large surface area of optical disks as a platform to grow tiny, upright zinc oxide nanorods about a thousandth the width of a human hair. Zinc oxide is an inexpensive semiconductor that can function as a photocatalyst, breaking apart organic molecules like the pollutants in sewage when illuminated with UV light.
As the disks are durable and able to spin quickly, contaminated water that drips onto the device spreads out in a thin film that light can easily pass through, speeding up the degradation. The team's complete water treatment device is approximately one cubic foot in volume. The device also consists of a UV light source and a system that recirculates the water to further break down the pollutants.
The team tested the reactor with a solution of methyl orange dye. After treating a half-litre solution for 60 minutes, they found that over 95% of the contaminants had been broken down.
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