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Lab. on Chemical Redox Acceleration Technologies for Water Quality

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Quantitative Photoelectrochemical Conversion of Ammonium to Dinitrogen Using Bromide-Mediated Redox Cycle
Year of publication 2021
Title of paper Quantitative Photoelectrochemical Conversion of Ammonium to Dinitrogen Using Bromide-Mediated Redox Cycle
Author Min Seok Koo, Seungmok Han, Kangwoo Cho, and Wonyong Choi*
Publication in journal ACS Environmental Science & Technology Engineering
Status of publication accepted
Vol 1
Link https://pubs.acs.org/doi/abs/10.1021/acsestengg.1c00119 24회 연결

Bromide ion (Br) can be oxidized to reactive bromine species (RBS; Br, Br2•–, and HOBr/OBr) which can serve as an effective alternative to chlorine disinfectant. This study investigated the generation of RBS in a photoelectrochemical (PEC) system using an electrochromic TiO2 nanotube arrays (Blue-TNTs) electrode under UV light (λ > 320 nm) and demonstrated the effect of RBS on the direct conversion of ammonium (NH4+) to dinitrogen (N2) with near 100% efficiency. The PEC system utilizing in situ generated RBS not only removed NH4+ more efficiently than photocatalytic (PC) and electrochemical (EC) systems but also prevented the generation of unwanted products (i.e., NO2 and NO3). In addition, compared with the PEC-Cl system, the PEC-Br system exhibited a superior ammonium removal efficiency (16% vs 95% for 120 min of reaction; under air-equilibrated condition). The PEC system also showed higher NH4+ removal efficiency and lower energy consumption when compared to an EC system (using a boron-doped diamond electrode). While bromate ions (BrO3) are produced as a toxic byproduct of bromide oxidation in a typical ozonation system, the Blue-TNTs PEC-Br system fully hinders the bromate formation as long as ammonium is present in the solution because RBS rapidly reacts with NH4+ with little chance of further oxidation to bromate.