Solar Purifier Creates its Own Disinfectant
A hiker gets disoriented while on a desert trek when she comes upon a drying puddle left by a recent rain.
Consumed by thirst, miles from home, the hiker must decide whether to drink and risk infection from whatever bacteria are in the puddle, or endure dehydration. But that hiker might one day be able to drink worry free, thanks to a new kind of water purifier that uses sunlight and water to produce hydrogen peroxide, a powerful and common antiseptic.
The experimental water purifier, developed in the lab of Xiaolin Zheng, associate professor of mechanical engineering, is a variant of the better-known process of using solar energy to split water into hydrogen, a clean-burning fuel, and oxygen, a life-sustaining element. But, as the team describes in the journal Advanced Energy Materials, instead of fully splitting oxygen and hydrogen, the new process reduces oxygen and oxidizes water to produce hydrogen peroxide, or H2O2.
Even just a small amount will purify the water, she says. Hydrogen peroxide disinfects water at a level of tens of parts per million. That’s about two tablespoons in 25 gallons of water. In tests using tap water, the Stanford system easily reached well over 400 parts per million of H2O2 in five hours.