An efficient technique removes ammonia from agricultural wastewater

According to the World Health Organization, one in three people in the world do not have access to clean drinking water and basic sanitation services. These problems have only increased worldwide due to the effects of climate change. As a result, coupled with investment and operational costs, developing countries and vulnerable communities are most affected by the adverse effects of water scarcity.

“Water scarcity is one of the greatest challenges of the 21st century,” said David Estrada, associate professor of materials science and engineering. “In our lab, we are committed to finding solutions to problems that do not respect political, socio-economic or cultural boundaries. This new system can be tailored to meet the water restoration needs of communities of various sizes and economic backgrounds around the world.

Boise State researchers from the College of Engineering joined researchers from Drexel University and the Idaho National Laboratory to study a simple, energy-efficient technique for removing ammonia from agricultural wastewater. The research was co-led by Estrada and Ted Lister, a chemical separations researcher in the Idaho National Laboratory’s Energy and Environmental Science and Technology Directorate. The group’s work is published in the Nature Partner Journal, Clean Water.

The research team used capacitive deionization, an emerging water purification technique in which water flows between two oppositely charged electrodes. This technique polarizes the ionic impurities in the wastewater, causing the ions to be attracted and stored in the opposite electrodes.

“It takes roughly 20 times more energy to synthesize ammonia from fossil fuels than to recover ammonia using our approach,” Lister said. “Such fossil fuel-based industrial processes can generate up to four times more carbon dioxide than the amount of ammonia that is synthesized, highlighting the importance of recycling our resources produced using such energy-intensive techniques.”

The team examined previous studies that investigated carbon-based materials as electrodes, but these materials were limited in terms of chemical diversity, surface chemistries, and surface area-to-volume ratio, which limited the effectiveness of the capacitive deionization technique. The team partnered with Drexel University’s Chris Shook and Yuri Gogotsi to explore a new approach using MXenes, an inorganic compound composed of layers of nitrides, carbonitrides, or metal carbides.

“MXenes have a unique combination of properties that make them very attractive for electrochemical applications,” said Naqsh Mansoor, a Boise State graduate student in Micron’s School of Materials Science and Engineering and first author of the paper. “The extended structure of MXenes allows for a lot of intercalation space so that the removed contaminants can not only adsorb on the surface, but also insert themselves between the layers.”

The team’s research found a 100-fold improvement in deionization capacity using MXenes compared to activated carbon-based electrode systems. This resulted in a greater number of pollutants being removed from the wastewater stream while using less of the electrode material.

Reference: Mansoor NE, Diaz LA, Shuck CE, Gogotsi Y, Lister TE, Estrada D. Ammonia removal and recovery from simulated wastewater using Ti3C2Tx MXene in capacitive flow electrode deionization. npj Pure water. 2022; 5 (1): 1-11. doi: 10.1038/s41545-022-00164-3

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