Access to clean water can be difficult in remote areas
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A simple jar with a crank could revolutionize the supply of drinking water to disaster areas and isolated communities without electricity.
Xu Deng, of the University of Electronic Science and Technology of China in Chengdu, says he and his colleagues were determined to create a simple way to rid water of parasites, as well as bacterial, viral and fungal pathogens.
“We kept running into the same obstacle with decentralized water treatment,” says Deng. “Most point-of-use options require electricity or strong sunlight, and they are slow.”
In off-grid communities and disaster areas, traditional systems are unreliable. So they were looking for an invention that could completely disinfect water in just one minute of simple manual shaking.
Their solution is based on spherical silica nanoparticles coated with amine group chemicals, which are positively charged in water, and gold nanoparticles, which become negatively charged in stirred water.
“Think of a hand-cranked pot containing a small dose of artificial sand-like powder,” says Deng. “A few turns of the handle create a slight shear in the water and this movement “wakes up” our nanoparticles.”
The flow of water over the surface of the gold and amine nanoparticles creates an electrical charge, in turn leading to the formation of oxidizing chemicals called reactive oxygen species.
“These reactive oxygen species puncture microbial membranes, preventing pathogens from surviving or reproducing,” explains Deng. “When you stop stirring, the powder separates from the water on its own and you draw clean water out the outlet.”
The team tested the device on 16 highly transmissible pathogens that pose a serious risk to public health. It got a 99.9999 percent reduction Escherichia coli with just 15 seconds of stirring the water at 50°C, and the same reduction in Vibrio Cholera in 1 minute. Overall, it inactivated more than 95 percent of all microorganisms tested.
The device is still in its proof-of-concept phase, Deng says, so researchers haven’t yet determined how many liters of water can be disinfected.
“What we can say is that the same batch of particles is recovered after each cycle and reused,” he explains. “And once charged, the system provides lasting protection against recontamination for several hours. »
Because the quantity of gold nanoparticles is so small, their cost is insignificant, he says: Material costs are dominated by the silica powder and the plastic casing.
Chiara Neto, from the University of Sydney, Australia, says she is extremely impressed by the science and the new application of nanoparticles to destroy the cell membranes of pathogens. “It’s very clever and fantastic work.”
