Millions of people around the world lack a source of clean, safe drinking water. Even more find themselves lacking purified water after disasters like earthquakes, tornadoes, and tsunamis. Now, a porous silver gel created from silver nanoparticles may hold the key to water purification for the masses. Traditional ways of cleaning dirty water, such as boiling, work to rid the water of parasites like Giardia. However, loss of power after a natural disaster renders power-dependent water purification methods useless.
Contaminated Water SourceImage: Wikimedia Commons
Created by scientists from Nanyang Technological University in Singapore and the University of Colorado, Boulder, the cheap and very effective gel sucks up dirty water, kills bacteria, and produces clean drinking water with just a squeeze. Spurred to their creation by the 2004 Indian Ocean tsunami, the researchers knew silver could kill bacteria as part of a filtration membrane. The trick, though, is preventing the silver from entering the water itself, as it could turn the purified water into poison.
2004 Indian Ocean TsunamiImage: U.S. Navy/Wikimedia Commons
They solved the problem by making a polymer gel of silver nanoparticles inside near-freezing water. This caused ice to form in the finished silver gel. The scientists then dunked the gel in silver nitrate solution followed by a bath in sodium burohydride. This reducing agent removed all the silver ions, leaving the porous surfaces of the gel splattered with the silver nanoparticles. The result was a lightweight spongy material that was remarkably effective at water purification.
Silver Gel Water Purification Process: Silver Gel Water Purification Process
Image: Environmental Science Technology
They tested the material on contaminated water containing E. coli and B. subtilis bacteria. Within 15 seconds, the gel purified the dirty water to about 0.1% of the bacteria in the original sample. Leaving the water inside the gel for 5 minutes resulted in purified water with bacteria levels approximately one-millionth that of the source water. One cylinder containing 4 grams of the silver gel purified ½ liter of water with one squeeze, and was reusable for up to 20 squeezes with no loss of water purification power.
One of the material’s creators, Xiao (Matthew) Hu, estimated a pocket-sized version of the silver gel water purification polymer would cost about 50 cents to make. Because it is so light, it would be easily portable. The gooey water purifier acts like a bacteria killing sponge, and requires no electricity or other power source to work. The level of bioavailable silver remaining in the purified water falls well within the safe limits established by the World Health Organization.
Clean Glass of Water: Clean Water
Image: Unconstructive Bryan/Flickr Commons
Water purification gel capsules could be dropped into disaster zones via helicopters, or provided to people in cases people keep with them. Getting drinking water would be as simple as dipping the gel in any water, waiting a few seconds, and squeezing the water directly into the mouth.
The next step is field-testing the miracle water purifying gel on contaminated water. The Lien Foundation, based in Singapore, will assist with the testing in water-needy areas of Myanmar. Researchers are also working on creating automated ways to purify large quantities of drinking water using the silver gel.
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