Quantitative Photoelectrochemical Conversion of Ammonium to Dinitrogen Using a Bromide-Mediated Redox Cycle
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2021-07-26 |
| Journal | ACS ES&T Engineering |
| Authors | Min Seok Koo, Seungmok Han, Kangwoo Cho, Wonyong Choi |
| Institutions | Pohang University of Science and Technology |
| Citations | 20 |
Abstract
Section titled āAbstractāBromide ion (Br-) can be oxidized to reactive bromine species (RBS; Brā¢, Br2ā¢-, 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 (Ī» > 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.