Pharmaceuticals, including antibiotics, are an increasingly common pollutant in water systems, said Catherine Hui Niu, associate professor in the Department of Chemical and Biological Engineering at the University of Saskatchewan.
After pharmaceuticals are used in humans and animals, traces are excreted and end up in sewage and, from there, into the environment. Their presence in waterways has raised concerns about potential risks to human health and ecosystems. To date there has been no effective way to remove them from water sources.
There are some materials that attract pharmaceutical pollutants to them in a process called adsorption, and could hypothetically be used to help remove them from water, says Niu. But their adsorption capacities need to be enhanced to make them useful for large scale clean-up efforts.
Barley straw, the leafy part of barley plants, has adsorption properties that show promise for helping remove certain antibiotics from water.
Niu and Bei Yan, a member of her research team, used the Canadian Light Source at the University of Saskatchewan to study samples of pretreated barley straw exposed to norfloxacin. It's a type of quinolone antibiotic commonly used to treat bladder infections and a few other conditions, and has been detected as a pollutant in some water and sewage samples.
The scientists' work revealed some of the mechanisms of how the pretreated barley straw works as an adsorbent. They found that subjecting the straw to a chemical and microwave heating protocol actually improved its adsorption qualities, specifically for removing the antibiotic norfloxacin from water. These results have been published in Chemical Engineering Journal.
"The pretreated barley straw's adsorption capacity is much higher than many other materials out there," said Niu.
In fact, it is about six times higher than that of untreated raw barley straw.
All of this is still at a laboratory stage, cautions Niu. But understanding the mechanisms is an important step for developing eco-friendly materials than can help remove antibiotics such as norfloxacin from water.
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Bei Yan et al. Kinetics, electron-donor-acceptor interactions, and site energy distribution analyses of norfloxacin adsorption on pretreated barley straw, Chemical Engineering Journal (2017). DOI: 10.1016/j.cej.2017.08.056