Improving Membrane Technology for Water Treatment

UMass Amherst polymer chemist receives NSF grant to develop new filter technology
Todd Emrick

AMHERST, Mass. ­– The National Science Foundation (NSF) recently announced three-year, $162,770 collaborative research awards each to polymer chemist Todd Emrick at the University of Massachusetts Amherst and chemical engineer Benny Freeman at the University of Texas at Austin, who will work together to explore new ways to make energy-efficient, self-cleaning water purification membranes for municipal wastewater treatment and industrial and agricultural applications.

Water purification is a critically important behind-the-scenes challenge of modern life, Emrick explains. Many steps in the process begin with removing particles or other contaminants from water, for example, oil droplets from hydraulic fracturing flowback. But the filters inevitably become dirty and clogged, leading to seriously reduced performance and increased energy consumption, he and Freeman point out.

Emrick says, “There are membranes in use everywhere to remove salt, proteins, bacteria, oils and all types of organic matter from water. These can be large units in a desalination plant next to the ocean, or tiny filters in a device that separates DNA and proteins from serum in a medical lab. Hydraulic fracturing is an emerging place where rapid, efficient water cleanup is crucial, and this project is responding to this widespread, pressing need.”

The polymer chemist adds, “If we can give someone a membrane that lasts longer and resists degradation during cleaning, if my group can provide a coating to enable that, it would have a real societal benefit.”

This research program builds upon previous encouraging joint findings by Emrick and Freeman showing how to modify the surfaces of membranes so that particulate material such as oil droplets and other particles are less likely to stick to the membrane surface and clog the pores.

Emrick says, “Typically synthetic chemists and engineers speak different languages, but Benny and I have been working together for years, and we are coming up with ways to fluidly combine polymer chemistry and membrane engineering science.  Working in isolation, I wouldn’t know how to implement polymer coatings effectively, or even know if the membrane properties were improving. And, I think that Benny is very happy to not have to synthesize polymers. But working together, we can elevate the field because we bridge those chemistry and engineering disciplines.”

Specifically, the researchers will borrow from biology to develop new phosphorylcholine (PC)-substituted polyolefins for coating water purification membranes, such as microfiltration, ultrafiltration, and reverse osmosis membranes. This approach mimics properties of the phospholipid head group in human cells, placing those units onto a polymer framework. The biocompatible combination makes the resulting plastic very averse to sticking to oils and should improve membrane performance in the presence of surfactants, Emrick says.

Second, he and Freeman will experiment with preparing phenolic-containing phosphorylcholine polymers that combine non-fouling zwitterions, neutral molecules with equal numbers of positive and negative charges, with surface adhering structures that make the coatings resistant to washing off the surface prematurely as water passes over and through the membrane.

Both approaches hold the promise of dramatic improvement in membrane performance compared to materials in use today, the collaborators say. They plan to include frequent graduate student exchanges between their labs along with teleconference meetings to enhance the educational aspects of the joint project and ensure and effective collaboration.

Emrick, whose other research projects involve using synthetic polymer chemistry for numerous applications in water-rich environments (such as drug and gene delivery in vivo), was recently named to the American Chemical Society’s 2014 class of Fellows, which recognizes scientists who have demonstrated “outstanding accomplishments in chemistry and made important contributions to ACS, the world’s largest scientific society.” He and 98 other new ACS Fellows will be recognized at a ceremony on Aug. 11 during the ACS national meeting in San Francisco.