Article courtesy of Gail Bambrick | October 30, 2014 | Phys.org | Shared as educational material
(Phys.org) —Fracking for oil and gas is a dirty business. The process uses millions of gallons of water laced with chemicals and sand. Most of the contaminated water is trucked to treatment plants to be cleaned, which is costly and potentially environmentally hazardous.
A Tufts engineer is researching how to create membranes for filters that may one day be able to purify the water right at a fracking site. Ayse Asatekin, an assistant professor of chemical and biological engineering, is designing materials for sophisticated filters that would be more cost-effective and use less energy than current methods. They would work not only at fracking sites, but could also be used to clean industrial waste from manufacturing and pharmaceutical companies and to provide clean drinking water.
Using filters to purify water isn’t new. Hippocrates, in the fourth century B.C., invented a bag filter to trap sediments that caused water to smell and taste bad, while Sanskrit writings from 2000 B.C. describe sand and gravel filtration. Water is still filtered using the same basic principle: force it through a porous membrane that traps large particles while allowing clean water to pass through.
But to catch certain chemicals, you need a membrane with pores that measure just one nanometer across. For perspective, a strand of human hair is some 60,000 nanometers wide.
For this nanotechnology, Asatekin has turned to polymers—molecules strung together to form long chains. “A polymer is like a necklace of beads,” Asatekin says. “You can make a long chain or a short chain; you can make branches going off it. By playing with all these things, you can control a polymer’s configuration and its properties.”
She’s using the polymer chains to create a grid of ultra-small pores capable of snaring the tiniest pollutants. These nano-membranes are working in the lab, and will soon be ready to be designed for specific uses, manufactured and tested in the field.
But someday, in addition to being small, Asatekin’s polymer filters will also be smart: she’s experimenting with polymers that could distinguish between different chemicals. “So even if two molecules were the same size, the polymer would ‘know’ that one has certain functional groups that the other lacks, and be able to block it,” she says.