Though we often take it for granted, access to safe drinking water is a major problem in many parts of the world—especially in the wake of a natural disaster. Now, researchers have succesfully tested a new, lightweight, and—most importantly—cheap gel that sucks up water, kills bacteria in seconds, and returns the water in a perfectly drinkable form with nothing more than a squeeze.
Inspired by the Indian Ocean tsunami in 2004, the team of materials scientists and environmental engineers behind the gel decided to work with silver nanoparticles for their ability to efficiently kill bacteria when part of a filtration membrane. But doing so posed an issue—any silver leaking into the water could render it poisonous. They managed to overcome this problem, though, by synthesizing the polymer gel in near-freezing water. This way, ice would form in certain spots in the finished gel product, so when the researchers immersed the gel in a silver nitrate solution followed by sodium burohydride (a reducing agent that took out silver ions), the pore surfaces of the gel would be splattered with silver nanoparticles. And the resulting lightweight, spongy material proved wildly effective.
Testing it on water laced with Escherichia coli and Bacillus subtilis, the team found that a mere 15 seconds in the gel returned water that had about 0.1% the amount of bacteria as was in the original sample. Upping the in-gel time to 5 minutes gave them water that contained contaminated levels roughly one-millionth that of the source. What's more, you don't need a lot of the stuff. Just one 4g cylinder 1.5 cm in diameter and cm long will purify half a liter of water in one squeeze—and that can happen up to 20 times without any loss of effectiveness.
Xiao Hu, one of the material's creator, estimates that a pocketable version of the polymer would only cost about 50 cents to produce, and it's lightweight status means easy portability. So for people affected by a lack of drinking water for whatever reason, help should hopefully be on the way soon. [Chemical & Engineering News via PopSci]