Scientists ID new catalyst for cleanup of nitrites

November 25, 2013
Researchers at Rice University's Catalysis and Nanomaterials Laboratory have found that gold and palladium nanoparticles can rapidly break down nitrites. Credit: M.S. Wong/Rice University

Chemical engineers at Rice University have found a new catalyst that can rapidly break down nitrites, a common and harmful contaminant in drinking water that often results from overuse of agricultural fertilizers.

Nitrites and their more abundant cousins, , are that are often found in both groundwater and surface water. The compounds are a health hazard, and the Environmental Protection Agency places strict limits on the amount of nitrates and nitrites in . While it's possible to remove nitrates and nitrites from water with filters and resins, the process can be prohibitively expensive.

"This is a big problem, particularly for agricultural communities, and there aren't really any good options for dealing with it," said Michael Wong, professor of chemical and biomolecular engineering at Rice and the lead researcher on the new study. "Our group has studied engineered gold and palladium nanocatalysts for several years. We've tested these against chlorinated solvents for almost a decade, and in looking for other potential uses for these we stumbled onto some studies about palladium catalysts being used to treat nitrates and nitrites; so we decided to do a comparison."

Catalysts are the matchmakers of the molecular world: They cause other compounds to react with one another, often by bringing them into close proximity, but the catalysts are not consumed by the reaction.

In a new paper in the journal Nanoscale, Wong's team showed that engineered nanoparticles of gold and palladium were several times more efficient at breaking down nitrites than any previously studied catalysts. The particles, which were invented at Wong's Catalysis and Nanomaterials Laboratory, consist of a solid gold core that's partially covered with palladium.

Many areas of the United States are at risk of contamination of drinking water by nitrates and nitrites due to overuse of agricultural fertilizers. Credit: USGS

Over the past decade, Wong's team has found these gold-palladium composites have faster reaction times for breaking down chlorinated pollutants than do any other known catalysts. He said the same proved true for nitrites, for reasons that are still unknown.

"There's no chlorine in these compounds, so the chemistry is completely different," Wong said. "It's not yet clear how the gold and palladium work together to boost the reaction time in nitrites and why reaction efficiency spiked when the nanoparticles had about 80 percent palladium coverage. We have several hypotheses we are testing out now. "

He said that gold-palladium nanocatalysts with the optimal formulation were about 15 times more efficient at breaking down nitrites than were pure palladium nanocatalysts, and about 7 1/2 times more efficient than catalysts made of palladium and aluminum oxide.

Wong said he can envision using the gold- catalysts in a small filtration unit that could be attached to a water tap, but only if the team finds a similarly efficient for breaking down nitrates, which are even more abundant pollutants than nitrites.

"Nitrites form wherever you have nitrates, which are really the root of the problem," Wong said. "We're actively studying a number of candidates for degrading nitrates now, and we have some positive leads."

Explore further: Researchers shed new light on catalyzed reactions

More information:

Related Stories

Researchers shed new light on catalyzed reactions

November 19, 2008

Rice University scientists on the hunt for a better way to clean up the stubborn pollutant TCE have created a method that lets them watch molecules break down on the surface of a catalyst as individual chemical bonds are ...

Platinum nanocatalyst could aid drugmakers

August 31, 2009

( -- Nanoparticles combining platinum and gold act as superefficient catalysts, but chemists have struggled to create them in an industrially useful form. Rice University chemists have answered the call this week ...

Researchers create more efficient hydrogen fuel cells

March 15, 2012

Hydrogen fuel cells, like those found in some "green" vehicles, have a lot of promise as an alternative fuel source, but making them practical on a large scale requires them to be more efficient and cost effective.

The dance of the atoms

June 10, 2013

( —Catalysts can stop working when atoms on the surface start moving. At the Vienna University of Technology, this dance of the atoms could now be observed and explained.

Unexpected behavior of well-known catalysts

June 19, 2013

Industrial palladium-copper catalysts change their structures before they get to work, already during the activation process. As a result, the reaction is catalysed by a catalyst that is different from the one originally ...

Recommended for you

Physicists develop new technique to fathom 'smart' materials

November 26, 2015

Physicists from the FOM Foundation and Leiden University have found a way to better understand the properties of manmade 'smart' materials. Their method reveals how stacked layers in such a material work together to bring ...

Mathematicians identify limits to heat flow at the nanoscale

November 24, 2015

How much heat can two bodies exchange without touching? For over a century, scientists have been able to answer this question for virtually any pair of objects in the macroscopic world, from the rate at which a campfire can ...

New sensor sends electronic signal when estrogen is detected

November 24, 2015

Estrogen is a tiny molecule, but it can have big effects on humans and other animals. Estrogen is one of the main hormones that regulates the female reproductive system - it can be monitored to track human fertility and is ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.