According to a recently published study on the American Chemical Society journal ACS Catalysis, a team of engineering researchers from Rice University has developed a nanoparticle-based catalyst that can speed up the transformation of nitrates contaminant in drinking water into air and water.
Nitrogen is in the fertilizers that are applied in the huge quantities for gardening and farming. In the soil, bacteria convert various forms of nitrogen to nitrate, or NO3-, a desirable for plants uptake. But it is also a contaminant in drinking water and poses serious health hazards for infants, pregnant women, nursing mothers, or seniors. It gets transformed into nitrite (NO2-) in the human digestive system and takes away the oxygen-carrying ability of hemoglobin.
Nitrate pollution in the underground water source is common in agricultural communities. The concentration of this colorless, odorless, and tasteless substance in drinking water are monitored and regulated by the Environmental Protection Agency. In 1962, the U.S. Public Health Service adopted drinking water standards and set the recommended limit for nitrate-nitrogen at 10 mg/L.
The current practice of nitrate removal involves the use of ion-exchange filters. These filters can remove nitrates from the water, but need to be rejuvenated with fresh water every a few months. The rejuvenating process returns a concentrated dose of nitrates to the local water system.
Michael Wong's lab at Rice University specializes in developing nano-sized metal particles that speed up chemical reactions. Their 2013 study demonstrated that a type of gold-palladium particles can catalyze the reduction of nitrites with excellent efficiency, but are not suitable for catalyzing the reduction of nitrates.
The Wong lab changed the components of their particles this time: by covering 40 percent surface area of their nanoscale palladium spheres with indium oxide, they achieved a 50 percent increase of in efficient compared to their previous design. With the efficency like this, it is considerable that these particle catalysts can be soon deployed to treat contaminated water and help turn nitrates into nitrogen (the reduction product from the chemical reaction) and water.
The engineers did not stopping at the end of engineering, they also explored the chemistry behind the catalysis reaction. With helps from collaborators in Purdue University and University of Houston, the Rice team discovered that the indium speeds up the breakdown of nitrates while the palladium apparently keeps the indium from being permanently oxidized.
Commenting on what their future plan is, Wong said his team will work with industrial partners and other researchers to turn the process into a commercially viable water-treatment system.
Wong’s lab is a part of the Nanotechnology Enabled Water Treatment (NEWT) Center. Their project showcased the best what NEWT has to offer. The multi-institutional engineering research center based at Rice University is all about translating basic science and engineering discoveries into real-world solutions. It was established by the National Science Foundation in 2015 to develop compact, mobile, off-grid water-treatment systems that can provide clean water to millions of people and make U.S. energy production more sustainable and cost-effective.
NEWT Center will use nanotechnology to transform water treatment. Credit: Rice University