The research of steady-state electrochemical kinetics of effective and selective conversion of total nitrogen to N2
2019
Ye, Zhiping | Shen, Ruxue | Zhou, Xule | Yao, Jachao | Wang, Jade
The electrochemical conversion of inorganic nitrogen forms (i.e., NO₃⁻-N, NO₂⁻-N, and NH₄⁺-N) to N₂ was studied using Ti as cathode and Ti/PbO₂ as anode in the simulated wastewater. According to linear sweep voltammetry, nitric nitrogen was effectively converted to N₂ on Ti cathode at the working potential more negative than − 1.1 V (vs. SCE). Ti/PbO₂ anode had the working potential of + 0.8 V (vs. SCE) for NH₄⁺-N converted to N₂. The apparent rate constants of NO₃⁻-N to NO₂⁻-N and NO₂⁻-N to N₂ were 2.46 × 10⁻² min⁻¹ and 4.03 × 10⁻² min⁻¹, respectively. The kinetic analyses revealed that the reduction of NO₃⁻-N was a two-step process, and NO₂⁻-N was an unstable intermediate, which could be easily oxidized to NO₃⁻-N or reduced to NH₄⁺-N. The majority of NH₄⁺-N could be effectively converted to N₂ on Ti/PbO₂ anode with the apparent rate constants of 5.12 × 10⁻² min⁻¹. The dual-chamber (DC) reactor with circulation was used in the batch electrolysis of simulated and actual wastewater. The results verified the pathways of NH₄⁺-N oxidation and NO₃⁻-N reduction and achieved high conversion rate of total nitrogen (TN) to N₂.
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