Electrochemical reduction of nitrate in a catalytic carbon membrane nano-reactor

•A catalytic carbon membrane nano-reactor was designed for electro-reduction of nitrate.•High nitrate removal (90%) and selectivity (97%) to N2 in a single-pass is achieved.•Ideal result is stemmed from the reactions of *NO3 to *NO2, *NO and *N2.•Efficient nitrate removal also originates from high t...

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Published in:Water research (Oxford) 2022-01, Vol.208, p.117862-117862, Article 117862
Main Authors: Ma, Jing, Wei, Wei, Qin, Guotong, Xiao, Tianliang, Tang, Weiqiang, Zhao, Shuangliang, Jiang, Lei, Liu, Shaomin
Format: Article
Language:English
Subjects:
Bimetal catalysts
Carbon
Carbon membrane
Catalysis
Electrochemical reduction
Nano-reactor
Nitrate
Nitrates
Nitrogen
Nitrogen Oxides
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Summary:•A catalytic carbon membrane nano-reactor was designed for electro-reduction of nitrate.•High nitrate removal (90%) and selectivity (97%) to N2 in a single-pass is achieved.•Ideal result is stemmed from the reactions of *NO3 to *NO2, *NO and *N2.•Efficient nitrate removal also originates from high triple phase boundary area. Nitrate pollution is a critical environmental issue in need of urgent addressing. Electrochemical reduction is an attractive strategy for treating nitrate due to the environmental friendliness. However, it is still a challenge to achieve the simultaneous high activity and selectivity. Here we report the design of a porous tubular carbon membrane as the electrode deposited with catalysts, which provides a large triple-phase boundary area for nitrate removal reactions. The achieved nitrate removal rate is one order of magnitude higher than other literatures with high nitrate conversion and high selectivity of nitrogen. The carbon membrane itself had a limited catalytic property thus Cu-Pd bimetal catalysts were deposited inside the nano-pores to enhance the activity and selectivity. When Na2SO4 electrolyte was applied, the achieved single-pass removal of nitrate was increased from 55.15% (for blank membrane) to 97.12% by adding catalysts inside the membrane. In case of NaOH as the electrolyte, the single-pass nitrate removal efficiency, selectivity to nitrogen formation and nitrate removal rate was 90.66%, 96.40% and 1.47 × 10−3 mmol min−1 cm−2, respectively. Density functional theory studies demonstrate that the loading of bimetal catalysts compared with single metal catalysts enhances the adsorption of *NO3 on membrane surface favorable for N2 formation than NH3 on Cu-Pd surface. The application of catalytic carbon membrane nano-reactors can open new windows for nitrate removal due to the high reactor efficiency. [Display omitted]
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2021.117862