A dash ofrutheniumatoms on a copper nanowire might be one step toward a revolution in the global ammonia industry that also serves the environment.
Collaborators at Rice UniversitysGeorge R. Brown School of Engineering, Arizona State University, and Pacific Northwest National Laboratory have developed a high-performance catalyst that can, with near 100% efficiency, help extract ammonia and solid ammonia also known as fertilizer from low levels of nitrates that are prevalent in industrial wastewater and polluted groundwater.
A study led by Rice chemical and biomolecular engineerHaotian Wang shows that a process converts nitrate levels of 2,000 parts per million into ammonia, followed by an efficientgas stripping process for ammonia product collection. The remaining nitrogen contents after these treatments may be reduced to drinkable levels as defined by the World Health Organization.
According to graduate student Feng-Yang Chen, we completed a comprehensive water denitrification process. We may return industrial wastewater to drinking water if further water treatment is necessary.
Chen is one of the three leading authors of the book that is now available in Nanotechnology.
The study demonstrates a promising alternative to effective processes for an industry that is dependent on an energy-intensive process to produce more than 170 million tons of ammonia per year.
These scientists discovered from previous experiments that ruthenium molecules are a champ at catalyzing nitrate-rich wastewater. Their challenge was combining it with copper to suppress thehydrogen evolution reaction, a technique to produce hydrogen from the water that in this case is an unwanted side effect.
We also knew that ruthenium was a good metal candidate for nitrate reduction, but we also knew there was a big problem, that it might easily have a competing reaction, which is hydrogen evolution. Many electrons would then go to hydrogen, not the product we want.
We fashioned a concept from other fields, such as carbon dioxide reduction, that uses copper to prevent hydrogen evolution. Eventually, we had to find a solution to organically combine ruthenium and copper. It turns out that dispersing single ruthenium molecules into the copper matrix is the best.
According to Christopher Muhich, an assistant professor of chemical engineering at Arizona State, ruthenium atoms simplify the chemical path that connects nitrate and ammonia.
The water provides hydrogen atoms when there is only copper. On the one ruthenium sites water doesnt compete as well, providing just enough hydrogen without taking up spots for nitrate to react.
The process is performed at room temperature and under ambient pressure, and at what scientists referred to as an industrial-relevant nitrate reduction current of 1 amp per square centimeter, the amount of electricity needed to increase catalysis rates. That should make it simple to scale up.
I believe this has significant potential, but it has been ignored because it was difficult for previous studies to achieve such a high current density while still maintaining good product selectivity, according to a researcher. Now, they were showing just that. Im confident that this process will be used for industrial applications, particularly because it doesn''t require much infrastructure.
The primary benefit of the process is the reduction of carbon dioxide emissions from traditional industrial production of ammonia. These are not unusual, owing to 1.4 percent of the world''s annual emissions.
Wang said that although we understood that switching nitrate wastes to ammonia might not be able to fully replace the existing ammonia industry in the short term, this process might be significant contribution to decentralized ammonia production, especially in areas with high nitrate sources.
Along with the first investigation, Wangs lab and the of Rice environmental engineerPedro Alvarez, who lead theNanotechnology Enabled Water Treatment Center, have recently published a paper in the Journal of Physical Chemistry enebrated the use of cobalt-copper nanoparticles on a 3D carbon fiber paper substrate as an efficient catalyst to synthesize ammonia from nitrate reduction. This low-cost catalyst also gave great potential for denitrification in wastewater.
Rice graduate student Zhen-Yu Wu and Srishti Gupta, a graduate student at Arizona State University, are co-authors; research scientist Guanhui Gao, Jung Yoon Kim and Peng Zhu, and Yimo Han, an assistant professor of materials science and nanoengineering at Rice; Zou Finfrock, Hua Zhou and Graham King of Canadian Light Source, Saskatoon, Saskatchewan; and David Cullen of Oak Ridge National Laboratory
Daniel Perea of the Pacific Northwest lab has been a co-author of the paper. Wang is the Chair of the William March Rice Trustee and an assistant professor of chemical and biomolecular engineering.
The National Science Foundation''s Nanosystems Engineering Research Center for Nanotechnology Enabled Water Treatment (1449500) and the Welch Foundation (C-2051-20200401, C-2065-20210327) aided the study.