Silver nanoparticles in porous gel becomes bacteria-killing sponge for water purification

Drinking water from spigot
CC BY 3.0 DFID

After natural disasters, one critical element necessary for human survival is clean, drinkable water, which can be hard to come by if the water infrastructure is damaged or tainted. While there already are plenty of solutions for filtering and purifying water, some of them require access to power, or they are too slow or too expensive to effectively meet the drinking water needs of large amounts of people.

But a new material could be a cost-effective and simple way to turn potentially contaminated water into clean drinking water, with just a quick squeeze.

After seeing the effects of the Indian Ocean tsunami in 2004 on the ability for survivors to obtain drinking water, a group of scientists and engineers from the U.S. and Singapore were inspired to create an alternative method of water purification that would be faster and simpler than filtration or boiling.

The team worked with silver nanoparticles, as the material can effectively kill bacteria when applied to filter membranes, but they also wanted to be sure that the silver wouldn't leach out into the water during use. The solution lay in creating a porous polymer gel, which can quickly absorb water, and treating it with silver nanoparticles, which exposes the bacteria to the silver and effectively kills them.

© Environ. Sci. Technol.

"The researchers tested the gel by using it to sop up water laced with two troublesome bacterial species, Escherichia coli and Bacillus subtilis. After 15 seconds in the gel, the amount of bacteria in the water squeezed out was 0.1% that of the original levels. When the team increased the exposure time to five minutes, the amount of bacteria in the treated water was about one-millionth that of the tainted water. With such treatment times, the team could turn unsafe water into drinkable water." - CEN

Just four grams of the gel material were found to be able to absorb and disinfect half of a liter of water with just one cycle, and it can be reused more than 20 times and still be effective. The researchers say that because the new gel is so lightweight, disaster and emergency aid workers could easily deliver it to survivors via an airdrop, and that individual-sized gel treatments could be manufactured for less than 50 cents (USD) each.

The results of the team's work, "Superabsorbent Cryogels Decorated with Silver Nanoparticles as a Novel Water Technology for Point-of-Use Disinfection", is published at Environmental Science and Technology.

Tags: Drinking Water | Nanotechnology | Technology