Researchers have found a catalyst that can clean toxic nitrates from drinking water by converting them into air and water.
“Nitrates come mainly from agricultural runoff, which affects farming communities all over the world,” says lead study scientist Michael Wong, a chemical engineer at Rice University.
“Nitrates are both an environmental problem and health problem because they’re toxic. There are ion-exchange filters that can remove them from water, but these need to be flushed every few months to reuse them, and when that happens, the flushed water just returns a concentrated dose of nitrates right back into the water supply,” he explains.
Rice University’s indium-palladium nanoparticle catalysts clean nitrates from drinking water by converting the toxic molecules into air and water. (Credit: Jeff Fitlow/Rice)
Wong’s lab specializes in developing nanoparticle-based catalysts, submicroscopic bits of metal that speed up chemical reactions. In 2013, his group showed that tiny gold spheres dotted with specks of palladium could break apart nitrites, the more toxic chemical cousins of nitrates.
“Nitrates are molecules that have one nitrogen atom and three oxygen atoms,” Wong explains. “Nitrates turn into nitrites if they lose an oxygen, but nitrites are even more toxic than nitrates, so you don’t want to stop with nitrites. Moreover, nitrates are the more prevalent problem.
“Ultimately, the best way to remove nitrates is a catalytic process that breaks them completely apart into nitrogen and oxygen, or in our case, nitrogen and water because we add a little hydrogen,” he says.
“More than 75 percent of Earth’s atmosphere is gaseous nitrogen, so we’re really turning nitrates into air and water,” Wong adds.
Nitrates are toxic to infants and pregnant women and may also be carcinogenic. Nitrate pollution is common in agricultural communities, especially in the US Corn Belt and California’s Central Valley, where farmers use fertilizers heavily, and some studies have shown that nitrate pollution is on the rise due to changing land-use patterns.
Many areas of the United States are at risk for nitrate and nitrite contamination of drinking water due to overuse of agricultural fertilizers. (Credit: USGS)