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article imageWonder substance can treat contaminated water

By Tim Sandle     Aug 21, 2013 in Science
Contaminated water is a major problem in many parts of the world. To help people to get access to clean water, scientists have invented a porous gel embedded with silver nanoparticles that works like a bacteria-killing sponge.
The developed substance is a gel. When 'dirty' bacteria-laden water is passed through the gel, the gel can sanitize the water and produce water that is fit to be drunk. Technically the gel is a poly(sodium acrylate) (PSA) cryogel, which has been decorated with silver nanoparticles. Sodium polyacrylate is also known as 'waterlock'. The material has the ability to absorb as much as 200 to 300 times its mass in water.
The new substance, when paired with a specially designed tube device, is relatively easy to use. It works by the gel absorbing water, then binding and killing any bacteria that are present in a few seconds, and then releasing drinkable water when the gel is squeezed. To eliminate around 1000 cells of harmful bacteria, the water containing the contaminants only required fifteen seconds contact with the gel.
The reason that the bacteria are killed is due to the silver ions contained within the gel. Initially there was a concern that the silver could render the water toxic; however, the scientists were able to engineer a solution whereby the silver was mixed with the clean water produced after the gel is squeezed.
The researchers tested the gel by using it to soak up water laced with two bacterial pathogens: Escherichia coli and Bacillus subtilis. These pathogens, in low numbers were eliminated. When the researchers used a very high challenge (close to a million bacteria) they were also able to eliminate the microbes, although a longer, 15 minute contact time between the gel and the water was required.
A key advantage with the new invention is for parts of the world where contaminated water occurs and where resources are tight. This is because the gel is less expensive than most other water treatment processes, and can be used where there is no power and thus heating is not an option. A further advantage stems from the gel being recyclable for it can be used several times over without any loss to its bacteria killing properties. The process is also much faster than water filtration.
The gel is also very light and it is contained within a tube. The idea behind this is so that the gel could be dropped into disaster zones to allow people to access clean water quickly.
The new gel was designed by a group of scientists from Singapore and the U.S. The gel has been written up in a paper for the journal Environmental Science and Technology, in a paper titled "Superabsorbent Cryogels Decorated with Silver Nanoparticles as a Novel Water Technology for Point-of-Use Disinfection."
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