Engineers have developed a high-performance nanowire catalyst that pulls ammonia and solid ammonia (fertilizer) from nitrate, a common contaminant in industrial wastewater and polluted groundwater.
A dash of ruthenium atoms on a mesh of copper nanowires could be one step toward a revolution in the global ammonia industry that also helps the environment. Collaborators at Rice University's George R. Brown School of Engineering, Arizona State University and Pacific Northwest National Laboratory developed the high-performance catalyst that can, with near 100% efficiency, pull ammonia and solid ammonia -- aka fertilizer -- from low levels of nitrates that are widespread in industrial wastewater and polluted groundwater. A study led by Rice chemical and biomolecular engineer Haotian Wang shows the process converts nitrate levels of 2,000 parts per million into ammonia, followed by an efficient gas stripping process for ammonia product collection. The remaining nitrogen contents after these treatments can be brought down to "drinkable" levels as defined by the World Health Organization. "We fulfilled a complete water denitrification process," said graduate student Feng-Yang Chen. "With further water treatment on other contaminants, we can potentially turn industrial wastewater back to drinking water." Chen is one of three lead authors of the paper that appears in Nature Nanotechnology. The study shows a promising alternative toward efficient processes for an industry that depends upon an energy-intensive process to produce more than 170 million tons of ammonia per year. advertisement The researchers knew from previous studies that ruthenium atoms are champs at catalyzing nitrate-rich wastewater. Their twist was combining it with copper that suppresses the hydrogen evolution reaction, a way to produce hydrogen from water that in this case is an unwanted side effect. "We knew that ruthenium was a good metal candidate for nitrate reduction, but we also knew there was a big problem, that it could easily have a competing reaction, which is hydrogen evolution," Chen said. "When we applied…