One step toward a revolution in the global ammonia industry that also helps the environment is a dash of ruthenium atoms on a mesh of copper nanowires.
Rice University, Arizona State University, and Pacific Northwest National Laboratory collaborated to develop a catalyst that can pull ammonia and solid ammonia from low levels.
A study led by Rice chemical and biomolecular engineer Haotian Wang shows that 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 World Health Organization defines drinkable levels for the remaining nitrogen contents after these treatments.
The graduate student said that they fulfilled a complete water denitrification process.
Chen is one of the authors of the paper.
An industry that depends on an energy intensive process to produce more than 170 million tons of ammonia per year is showing a promising alternative to efficient processes.
The researchers knew that ruthenium atoms were good at catalyzing nitrate-rich wastewater. It is an unwanted side effect of combining it with copper that suppresses the hydrogen evolution reaction, a way to produce hydrogen from water.
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.
We borrowed a concept from other fields like carbon dioxide reduction, which uses copper to suppress hydrogen evolution. The best way to get single ruthenium atoms into the copper matrix is to distribute them into it.
The team used density functional theory calculations to explain why ruthenium atoms make the chemical path that connects nitrate and ammonia easier to cross.
The water gets in the way when there is only ruthenium. Water does not compete as well on the single ruthenium sites, providing just enough hydrogen without taking up spots for nitrate to react.
The process works at room temperature and under pressure, and at a nitrate reduction current of 1 Amp per square centimeter. Chen said that it should be easy to scale up.
I think this has big potential, but it has been ignored because it has been hard for previous studies to reach such a good current density, especially under low nitrate concentrations. I am confident that we will have opportunities to push this process for industrial applications because it doesn't require a lot of infrastructure.
Reduction of carbon dioxide emissions from traditional industrial production of ammonia is a prime benefit of the process. The researchers noted that these are not insignificant, amounting to 1.4% of the world's annual emissions.
The process of converting nitrate waste to ammonia may not be able to completely replace the existing ammonia industry in the short term, but we believe it could make a significant contribution to the production of ammonia in places with high nitrate sources.
A paper detailing the use of copper and cobalt nanoparticles on a 3D carbon fiber was published in the Journal of Physical Chemistry C. The catalyst showed promise for the denitrification of wastewater.
More information: Feng-Yang Chen et al, Efficient conversion of low-concentration nitrate sources into ammonia on a Ru-dispersed Cu nanowire electrocatalyst, Nature Nanotechnology (2022). DOI: 10.1038/s41565-022-01121-4 Citation: New process aims to strip ammonia from wastewater (2022, May 2) retrieved 2 May 2022 from https://phys.org/news/2022-05-aims-ammonia-wastewater.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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