Mini Review on the Photocatalytic Removal of Gaseous Ammonia: Current Statusand Challenges

Abstract

Ammoniagas (NH₃) is a notorious malodorous pollutant released mainly inagriculture and industry. With the increasing demand for ammonia, environmentalpollution caused by ammonia discharge has seriously threatened human health andsafety. Due to the discrete emission and low concentration of NH₃,photocatalytic oxidation is an economical and efficient treatment strategy. TiO₂,as a common photocatalyst, has been widely used by researchers for thephotocatalytic removal of NH₃. In addition, surface modification,element doping, semiconductor recombination and metal loading are used toimprove the utilization rate of solar energy and carrier of TiO₂ soas to find a catalyst with high efficiency and high N₂ selectivity.Further, at present, there are three main removal mechanisms of NH₃ photocatalytic oxidation: ·NH₂ mechanism, iSCR mechanism and N₂H₄ mechanism. Among them, N₂H₄ mechanism is expected to bethe main removal path of NH₃ photocatalytic oxidation in the futurebecause the removal process does not involve NO_x and nitrate. Thisreview summarizes recent studies on the photocatalytic oxidation of NH₃,focusing primarily on NH₃ removal efficiency, N₂ selectivity, and the underlyingremoval mechanisms. Additionally, the potential future applications of NH₃photocatalytic oxidation are discussed.

Keywords

Gaseousammonia / Photocatalytic oxidation / NH₃ removal / Reaction mechanism

Acknowledgments

The authors express gratitude to the National Key Technology Research and Development Project of China (2019YFC1906404) for providing financial support for this study.

Author Contributions

Y.W.: Writing—original draft, Investigation, Formal analysis. Y.Y.: Writing—review & editing. Y.G.: Writing—review & editing, Investigation. S.Y.: Writing—review & editing, Supervision, Resources, Project administration, Funding acquisition, Conceptualization.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Funding

This research was funded by the National Key Technology Research and Development Project of China (2019YFC1906404).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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