Low-temperature NO decomposition in humidified condition using plasma–catalyst system

Oxygenic denitrification for nitrogen removal with less greenhouse gas emissions: Microbiology and potential applications

Nitrogen pollution is a worldwide problem and has been extensively treated by canonical denitrification (CDN) process. However, the CDN process generates several issues such as intensive greenhouse gas (GHG) emissions. In the past years, a novel biological nitrogen removal (BNR) process of oxygenic denitrification (O2DN) has been proposed as a promising alternative to the CDN process. The classic denitrification four steps are simplified to three steps by O2DN bacteria without producing and releasing the intermediate nitrous oxide (N₂O), a potent GHG. In this article, we summarized the findings in previous literatures as well as our results, including involved microorganisms and metabolic mechanisms, functional genes and microbial detection, kinetics and influencing factors and their potential applications in wastewater treatment. Based on our knowledge and experience, the benefits and limitations of the current O2DN process were analyzed. Since O2DN is a new field in wastewater treatment, more research and application is required, especially the development of integrated processes and the quantitative assessment of the contribution of O2DN process in natural habitats and engineered systems.

A review on the catalytic decomposition of NO to N2 and O2: catalysts and processes

Recent advances in the catalytic decomposition of NO have been overviewed and divided into three categories: metal oxide catalysts (including perovskites and rare earth oxides), supported metal oxide catalysts (including alkali metals, cobalt oxide and noble metals) and Cu-ZSM-5.

Combining nonthermal plasma with perovskite-like catalyst for NOx storage and reduction

A new NOx storage and reduction (NSR) system is developed for NOx removal by combining perovskite-like catalyst with nonthermal plasma technology. In this hybrid system, catalyst is mainly used for oxidizing NO to NO2 and storing them, while nonthermal plasma is applied as a desorption-reduction step for converting NOx into N2. An innovative catalyst with a high NOx storage capacity and good reduction performance is developed by successive impregnation. The catalysts prepared with various metal oxides were investigated for NOx storage capacity (NSC) and NOx conversion. Characterization of the catalysts prepared reveals that addition of cobalt (Co) and potassium (K) considerably increases the performance for NSC. Results also show that SrKMn0.8Co0.2O4 supported on BaO/Al2O3 has good NSC (209 μmol/gcatalyst) for the gas stream containing 500 ppm NO and 5 % O2 with N2 as carrier gas. For plasma reduction process, NOx conversion achieved with SrKMn0.8Co0.2O4/BaO/Al2O3 reaches 81 % with the applied voltage of 12 kV and frequency of 6 kHz in the absence of reducing agents. The results indicate that performance of plasma reduction process (81 %) is better than that of thermal reduction (64 %). Additionally, mixed gases including 1 % CO, 1 % H2 and 1 % CH4, and 2 % H2O(g) are simultaneously introduced into the system to investigate the effect on NSR with plasma system and results indicate that performance of NSR with plasma can be enhanced. Overall, the hybrid system is promising to be applied for removing NOx from gas streams. Graphical abstract ᅟ.

The byproduct generation analysis of the NOx conversion process in dielectric barrier discharge plasma

Abatement of NO_x through non-thermal plasma (NTP) processes has been developed over the past several years.

Removal dynamics of nitric oxide (NO) pollutant gas by pulse-discharged plasma technique

Nonthermal plasma technique has drawn extensive attentions for removal of air pollutants such as NO_x and SO₂. The NO removal mechanism in pulse discharged plasma is discussed in this paper. Emission spectra diagnosis indicates that the higher the discharge voltage is, the more the NO are removed and transformed into O, N, N₂, NO₂, and so forth. Plasma electron temperature T_e is ranged from 6400 K at 2.4 kV discharge voltage to 9500 K at 4.8 kV. After establishing a zero-dimensional chemical reaction kinetic model, the major reaction paths are clarified as the electron collision dissociation of NO into N and O during discharge and followed by single substitution of N on NO to form N₂ during and after discharge, compared with the small fraction of NO₂ formed by oxidizing NO. The reaction directions can be adjusted by N₂ additive, and the optimal N₂/NO mixing ratio is 2 : 1. Such a ratio not only compensates the disadvantage of electron competitive consumption by the mixed N₂, but also heightens the total NO removal extent through accelerating the NO oxidization process.