321 エキシマランプで励起したアンモニアガスの脱硝特性(排ガス処理(プラズマ))

To broaden and lower the temperature window of the selective non catalytic reduction (SNCR) of nitric oxide (NO), the use of activated ammonia as the reduction agant was examined. An intermittent dielectric barrier dischalge (DBD) was employed to generate activated ammonia from molecular ammonia. Chemical composition was clear by gas analysis at exit of the DBD reactor, it found that the main species of the activate ammonia were H_2 and N_2. By experiments and chemical kinetics simulation, it was clear that H_2 was strongly contributed to enlargement of temperature window ofDeNOx.

Complexing agents-free bioelectrochemical trickling systems for highly-efficient mesothermal NO removal: The role of extracellular polymer substances

The relationship between nitric oxide (NO) reduction and the inhibition of abscisic acid (ABA)-induced stomatal closure by ethylene was analysed. ABA treatment induced NO production and stomatal closure, but ethylene inhibited the effects of ABA on these two parameters. Like 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), a specific scavenger of NO, haemoglobin (Hb), the potent scavenger of NO/carbon monoxide (CO) and N G -nitro-L-Arg-methyl ester (L-NAME), an inhibitor of animal nitric oxide synthases (NOS; EC 1.14.13.39), both the ethylene-releasing compound 2-chloroethylene phosphonic acid (ethephon, ETH) and 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene, were found to inhibit stomatal closure by ABA and to reduce NO levels by ABA in guard cells, indicating that the ethylene-caused inhibition of ABA-induced stomatal closure involves a decrease in NO levels in guard cells. In addition, and similar to cPTIO and Hb, ACC/ETH suppressed sodium nitroprusside (SNP)-induced stomatal closure and NO levels in guard cells treated with SNP in the light. ACC/ETH also reopened stomata that had been closed by ABA and reduced NO levels that had been generated by ABA, showing that ethylene causes NO removal in guard cells. However, the above-mentioned effect of ACC/ETH was dissimilar to that of L-NAME, which was incapable of reducing NO levels by SNP or abolishing NO that had been generated by ABA. We suggest that ethylene probably induces NO removal, thereby reducing NO levels in Vicia faba guard cells, and finally inhibits stomatal closure induced by ABA. Furthermore, the pattern of NO reduction caused by ethylene is also discussed.

Simultaneous mercury oxidation and NO reduction in a membrane biofilm reactor

Simultaneous removal of NO and Hg0 using Fe and Co co-doped Mn-Ce/TiO2 catalysts

BACKGROUNDSelective non‐catalytic reduction (SNCR) is a proven technique to lessen nitric oxide (NO) emissions from stationary sources. However, the process using ammonia or urea as a reducing agent is only effective in a narrow and high temperature window, with the maximum NO abatement declining when increasing the oxygen (O2) content. Large industrial boilers may be often under a variable load and an excess of O2, which could decrease the effectiveness of the de‐NOx process. This study investigated hydrazine (N2H4) as a reagent to improve SNCR performance.RESULTSNO reduction by N2H4 was experimentally investigated in a pilot‐scale flow reactor. The effect of reaction temperature, molar ratio of NH2 to NO (normalized stoichiometric ratio, NSR), initial NO level and O2 concentration on the NO reduction in flue gas containing 7.4–17.4% (v/v) O2 at temperatures between 450 and 1100 °C was determined. The experimental results indicated that NO reduction by N2H4 was possible in dual temperature ranges, and the optimum reaction temperatures were about 580 and 1060 °C at NSR = 2.0. Moreover, the N2H4–NO reaction is less O2‐sensitive. A chemical kinetic model was developed to correctly describe the non‐catalytic reduction of NO by N2H4 in the presence of O2.CONCLUSIONHydrazine‐based SNCR is an alternative method for NO reduction occurring in dual temperature ranges and excess O2. The present model provided a satisfactory prediction of the experimental results, offering an effective tool for process simulation over a wide range of operating conditions. © 2019 Society of Chemical Industry

The constant surge in nitric oxide in the atmosphere results in severe environmental degradation, negatively impacting human health and ecosystems, and is presently a global concern. Widely used physicochemical technologies for nitric oxide (NO) removal comes with high installation and operational costs and the production of secondary pollutants. Thus, biological treatment has been emphasized over the last two decades, but the poor solubility of NO in water makes it a challenging issue. The present article reviews the various technical aspects of biological treatment of nitric oxide, including the removal pathways and reactor configurations involved in the process. The most widely used technologies in this regard are chemical adsorption processes followed by biological reactors like biofilters, biotrickling filters and membrane bioreactors that enhance NO solubility and offer the flexibility and scope of further improvement in process design. The effect of various experimental and operational parameters on NO removal, including pH, carbon source, gas flow rate, gas residence time and presence of inhibitory components in the flue gas, is also discussed along with the developed mathematical models for predicting NO removal in a biological treatment system. There is an extensive scope of investigation regarding the development of an economical system to remove NO, and an exhaustive model that would optimize the process considering maximum practical parameters encountered during such operation. A detailed discussion made in this article gives a proper insight into all these areas.

Graphene oxide (GO) was utilized to investigate the role of carboxylic acid groups in the reduction of nitric oxide (NO) for the first time. As a result, GO with sufficient carboxylic acid groups reduced 45% of NO at 100 °C. However, GO without these oxygen-containing groups barely reduced NO (lower than 5%) under the same conditions. After reduction of NO, the carboxylic acid group content on GO decreased from 8.32 to 5.22 mmol g-1. Simultaneously, the anhydride group content increased from 0.14 to 0.28 mmol g-1. FTIR spectroscopy also indicated that the carboxylic acid groups transformed into anhydride and lactone groups. Moreover, both transient kinetics and TG-MS studies demonstrated that reactive intermediates formed during the reaction between NO and GO at 100 °C. Based on these results, it was proposed that the carboxylic acid groups participated in NO reduction by consumption and regeneration. This mechanism explains why carbon is usually an effective reductant and catalyst support for NO removal at low temperature.

Efficient nitric oxide (NO) removal without nitrogendioxide(NO2 )emission is desired for the control of air pollution. Herein, a series of (Zr/Ti)UiO-66-NH2 with congenetic shell-core structure, denoted as Ti-UION, are rapidly synthesized by microwave-assisted post-synthetic modification for NO removal. The optimal Ti-UION (i.e., 2.5Ti-UION) exhibits the highest activity of 80.74% without NO2 emission with moisture, which is 21.65% greater than that of the UiO-66-NH2 . The NO removal efficiency of 2.5Ti-UION further increases to 95.92% without photocatalyst deactivation under an anhydrous condition. This is because selectively produced NO2 in photocatalysis is completely adsorbed into micropores, refreshing active sites for subsequent reaction. In addition, the enhanced photocatalytic activity after Ti substitution is due to the presence of Ti electron acceptor, the potential difference between the shell and core of Ti-UION crystal, and the high conductivity of TiO units. Additionally, the improved adsorption of gas molecules not only favors NO oxidation, but also avoids the emission of NO2 . This work provides a feasible strategy for rapid metal substitution in metal-organic frameworks and insights into enhanced NO photodegradation.

Chemical absorption-biological reduction (BioDeNOx), which uses Fe(II)(EDTA) as a complexing agent for promoting the mass transfer efficiency of NO from gas to water, is a promising technology for removing nitric oxide (NO) from flue gases. The carbon source and pH are important parameters for Fe(II)(EDTA)-NO (the production of absorption) reduction and N2O emissions from BioDeNOx systems. Batch tests were performed to evaluate the effects of four different carbon sources (i.e., methanol, ethanol, sodium acetate, and glucose) on Fe(II)(EDTA)-NO reduction and N2O emissions at an initial pH of 7.2 ± 0.2. The removal efficiency of Fe(II)(EDTA)-NO was 93.9%, with a theoretical rate of 0.77 mmol L(-1) h(-1) after 24 h of operation. The highest N2O production was 0.025 mmol L(-1) after 3 h when glucose was used as the carbon source. The capacities of the carbon sources to enhance the activity of the Fe(II)(EDTA)-NO reductase enzyme decreased in the following order based on the C/N ratio: glucose > ethanol > sodium acetate > methanol. Over the investigated pH range of 5.5-8.5, the Fe(II)(EDTA)-NO removal efficiency was highest at a pH of 7.5, with a theoretical rate of 0.88 mmol L(-1) h(-1). However, the N2O production was lowest at a pH of 8.5. The primary effect of pH on denitrification resulted from the inhibition of nosZ in acidic conditions.

The brain responds to hypoxia with an increase in cerebral blood flow (CBF). However, such an increase is generally believed to start only after the oxygen tension decreases to a certain threshold level. Although many mechanisms (different vasodilator and different generation and metabolism mechanisms of the vasodilator) have been proposed at the molecular level, none of them has gained universal acceptance. Nitric oxide (NO) has been proposed to play a central role in the regulation of oxygen supply since it is a vasodilator whose production and metabolism are both oxygen dependent. We have used a computational model that simulates blood flow and oxygen metabolism in the brain (BRAINSIGNALS) to test mechanism by which NO may elucidate hypoxic vasodilation. The first model proposed that NO was produced by the enzyme nitric oxide synthase (NOS) and metabolized by the mitochondrial enzyme cytochrome c oxidase (CCO). NO production declined with decreasing oxygen concentration given that oxygen is a substrate for nitric oxide synthase (NOS). However, this was balanced by NO metabolism by CCO, which also declined with decreasing oxygen concentration. However, the NOS effect was dominant; the resulting model profiles of hypoxic vasodilation only approximated the experimental curves when an unfeasibly low K m for oxygen for NOS was input into the model. We therefore modified the model such that NO generation was via the nitrite reductase activity of deoxyhemoglobin instead of NOS, whilst keeping the metabolism of NO by CCO the same. NO production increased with decreasing oxygen concentration, leading to an improved reproduction of the experimental CBF versus PaO2 curve. However, the threshold phenomenon was not perfectly reproduced. In this present work, we incorporated a wider variety of oxygen dependent and independent NO production and removal mechanisms. We found that the addition of NO removal via oxidation to nitrate mediated by oxyhemoglobin resulted in the optimum fit of the threshold phenomenon by the model. Our revised model suggests, but does not prove, that changes in NO concentration can be the primary cause of the relationship between pO2 and cerebral blood flow.

Effects of hydrogen addition on the removal of nitric oxide by cyanuric acid

99/03849 Latest design of a soda recovery boiler and process for gasification of black liquor: Duda, Z. Przegl. Papier., 1998, 54, (2),85–88. (In Polish)

Nitric oxide (NO) removal by aqueous sodium persulfate (Na2S2O8) simultaneously activated by temperature and Fe2+ was studied in a lab-scale bubble reactor. The effects of Na2S2O8 (0.01–0.20 M), Fe2+ (0.00–0.10 M), gas-phase NO (500–1000 ppm) concentrations, and temperatures (23–90 °C) were investigated. NO fractional conversion at all temperatures with and without the presence of Fe2+ increased sharply with persulfate concentration up to about 0.10 M before leveling off. At 0.10 M Na2S2O8 and 0.01 M Fe2+ concentrations, conversions of up to 79% and approximately 100% were observed at 70 and 90 °C, respectively. Increased temperature led to increased conversions of NO at all persulfate levels, and activation by 0.01 M Fe2+ further improved NO conversion by ∼10% at all temperatures. The chemistry of NO removal and proposed reaction pathways are discussed. The results demonstrated the feasibility of improved NO aqueous scrubbing by temperature- and Fe2+-activated persulfate.

Nitric oxide (NO) emission is known to pose detrimental effects towards the environment and human beings. Low-temperature NO removal by activated carbon from agricultural waste materials is affordable due to the use of low-cost materials as precursor and elimination of the need for flue gas reheating. The use of chemical agents in activated carbon production improves the performance of waste materials in NO removal. The performance of NO removal was investigated via breakthrough experiment using oil palm empty fruit bunch (EFB) activated with zinc chloride (ZnCl2) at different concentrations (0.1, 0.5, and 1.5 M). Activation of EFB with 0.5 M ZnCl2 resulted in the formation of well-defined micropores, but the use of higher concentration of ZnCl2 resulted in widening of developed pores and intense pore blockage which reduce the accessibility of NO molecules to the adsorption sites. An adsorption isotherm study conducted using 0.5 M ZnCl2/EFB sample with varying NO concentration between 300-1000 ppm indicated that the adsorption process was best defined by Langmuir isotherm model. In addition, adsorption kinetic was investigated at different temperatures; i.e. 100, 150, 200, 250 and 300 °C. NO removal was found to follow Avrami kinetic model at T=100 °C, while upon further increase in temperature, the process was better fitted to the pseudo-second order kinetic model. NO adsorption capacity increases significantly beyond 250 °C up to 1000 mg/g. The activation energy of NO adsorption fell into two distinct regions: -4.73 kJ/mol at 100-200 °C and 84.04 kJ/mol at 200-300 °C. At lower temperature, the adsorption process was exothermic and followed physisorption path, while the increase in reaction temperature led to slower rate of reaction. It was concluded that the removal of NO using EFB modified with ZnCl2 at optimized condition could be a promising alternatives for treating NO-containing flue gas.