Efficient electrochemical-catalytic reduction of nitrate using Co/AC0.9-AB0.1 particle electrode

Wenjian Ye; Wenwen Zhang; Xinxin Hu; Shuai Yang; Wenyan Liang

doi:10.1016/j.scitotenv.2020.139245

Efficient electrochemical-catalytic reduction of nitrate using Co/AC_0.9-AB_0.1 particle electrode

Sci Total Environ. 2020 Aug 25:732:139245. doi: 10.1016/j.scitotenv.2020.139245. Epub 2020 May 7.

Authors

Wenjian Ye¹, Wenwen Zhang¹, Xinxin Hu¹, Shuai Yang¹, Wenyan Liang²

Affiliations

¹ College of Environmental Science & Engineering, Beijing Forestry University, Beijing 100083, China.
² College of Environmental Science & Engineering, Beijing Forestry University, Beijing 100083, China. Electronic address: lwy@bjfu.edu.cn.

PMID: 32408042
DOI: 10.1016/j.scitotenv.2020.139245

Abstract

In this work, a composite particle electrode (Co/AC_x-AB_y) was proposed using cobalt as the catalyst, active carbon (AC) as the carrier, and acetylene black (AB) as the conductor. The proposed particle electrodes were applied in a continuous three-dimensional (3D) electrochemical reactor. Based upon the removal efficiency of total nitrogen (TN) and the corresponding energy consumption, the optimum mass ratio of AC to AB was determined to be 0.9:0.1. Scanning electron microscopy (SEM) and energy dispersive system (EDS)-mapping revealed the presence of metal particles on the surface of Co/AC_0.9-AB_0.1 electrode. Furthermore, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that Co/AC_0.9-AB_0.1 contained three valence states of Co, namely Co⁰, Co²⁺, and Co³⁺. Additionally, batch experiments showed that 95% of TN removal was achieved under the current of 0.4 A, pH of 7, hydraulic retention time (HRT) of 60 min and the initial TN of 20 mg/L. The addition of Cl^- was obviously beneficial to the removal of TN, whereas HCO₃^-, PO₄^3-, CO₃^2-, and dissolved organic matter (DOM) inhibited the removal of TN. The cyclic voltammetry (CV) curve and the atomic H detected by electron spin resonance (ESR) demonstrated that nitrate was directly reduced by Co⁰ ions and indirectly reduced by H radicals.

Keywords: Cobalt; Hydrogen radical; Three-dimensional electrode; Total nitrogen.