Access to clean water can be difficult in remote areas
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A simple jar with a crooked handle could revolutionize the delivery of clean drinking water in disaster zones and remote communities without power.
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 roadblock with decentralized water treatment,” says Deng. “Most point-of-use options either need electricity or strong sunlight, and they’re slow.”
In off-grid communities and disaster zones, traditional systems are not reliable, so they wanted an invention that could completely disinfect water with one minute of light, manual agitation.
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 the agitated water.
“Think of a hand-screwed jar with a small dose of engineered, sand-like powder,” says Deng. “A few turns of the handle creates a gentle displacement in the water, and that movement ‘wakes up’ our nanoparticles.”
The flow of water on the surface of the gold and amine nanoparticles creates an electrical charge that in turn leads to the formation of oxidizing chemicals called reactive oxygen species.
“These reactive oxygen species punch holes in microbial membranes so that pathogens cannot survive or reproduce,” says Deng. “When you stop stirring, the powder separates from the water on its own and you draw clean water from the outlet.”
The team tested the device on 16 highly transmissible pathogens that pose a serious risk to public health. It achieved a 99.9999 percent reduction in Escherichia coli with just 15 seconds of stirring the water at 50°C, and the same reduction in Vibrio cholerae within 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 the researchers have not 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 says. “And once charged, the system provides long-lasting protection against recontamination for many hours.”
Because the amount of gold nanoparticles is so small, their cost is negligible, he says – the cost of the materials is dominated by the silica powder and the plastic housing.
Chiara Neto at the University of Sydney, Australia, says she is very impressed with the science and the new use of nanoparticles to disrupt pathogens’ cell membranes. “It’s very smart, great work.”