Short Review of Self-Powered Nitrogen Removal via Abiotic Electrochemical Catalysis

Abstract

Microbial nitrification and denitrification are efficient technologies for the treatment of nitrogen-containing wastewater. However, these biotic technologies are inapplicable for the treatment of toxic substances such as heavy metals, polyaromatic hydrocarbons, adsorbable organic halogens, and polychlorinated biphenyls, which have an inhibitory effect on microbial metabolism. It is therefore necessary to develop abiotic nitrogen removal technology with comparable cost efficiency. Nitrogen contaminants are promising indirect fuel sources. The integration of electrocatalysis energy conversion with nitrogen contaminants could drive an entire electrochemical system to obtain nitrogen removal in a self-powered fashion. Research advances in the development of fuel cells have corroborated their promising application for nitrogen removal. This work aims to review the most recent advances in the utilization of ammonia and nitrate as fuels for self-powered nitrogen removal and demonstrate how close this technology is to integration with future applications. The mechanism of ammonia–oxygen fuel cells is first summarized, followed by an overview of recent research on self-powered systems based on various noble-metal-free catalysts. We then introduce different harvesting and conversion methods using nitrate with a desired power output and nitrogen removal efficiency. The final section demonstrates the shortcomings of research and future innovative perspectives for self-powered wastewater treatment.