Simultaneous Removal Of Nitric Oxide Research Articles

Streamlining manufacture of high-performance SiC catalytic membrane using bifunctional precursors for multipollutant control

SiC catalytic membrane holds great promise in controlling high-temperature nitric oxide (NO) and particulate matter (PM), but its complex fabrication process limits its potential for practical application. We present a novel, rapid fabrication route, based on co-sintering and acid treatment (CSAT), for the fabrication of Co3O4-loaded SiC (A-Co-SiC) catalytic membranes. Our approach involves using functional activated carbons and Co2O3 for the simultaneous sintering of both the support and separation layers at a lower temperature. The CSAT approach eliminates particle penetration into the support layer and accelerates the generation of active Co3O4 nanoparticles on Co2SiO4. This reduces the number of fabrication steps from 9 to 5, resulting in over a 50% reduction in both energy consumption and sintering time. The resulting A-Co-SiC catalytic membrane exhibits remarkable gas permeance of 224.51 m3 m−2 h−1·kPa−1, superior NO oxidation efficiency (85% at 280 °C), and a high PM2.5 filtration efficiency of 99.97% - the highest simultaneous removal of NO and PM2.5 reported to date. The manufacturing method developed in our work offers a practical and efficient solution for producing SiC catalytic membranes that can be utilized in various integrated emission filtration systems in industrial settings, with the potential to be adapted to other ceramic systems.

Treating waste with waste: Facile KHCO3-modified calcium carbide slag for simultaneous removal of NO and SO2

The simultaneous removal of nitric oxide (NO) and sulfur dioxide (SO2) in a cost-effective and environmentally friendly method is a major challenge in the field of industrial tail gas purification. In this study, the solid waste calcium carbide slag (CS) was modified by potassium bicarbonate (KHCO3) to achieve simultaneous removal of NO and SO2 under low temperature conditions. Experimental results confirmed that this low-cost KHCO3-modified calcium carbide slag (KCS) has excellent simultaneous removal of NO and SO2 activity, which is attributed to its unique morphology and abundant surface adsorbed oxygen species (Oads). Interestingly, the presence of SO2 improved the capacity of KCS for NO removal. In-situ diffuse reflectance infrared Fourier-transform spectroscopy results demonstrate that the addition of SO2 promote the formation of oxygen-containing functional groups. Further studies indicated that increasing the Oads could effectively facilitate oxidation of NO and SO2 to nitrate (NO3–) and sulfate (SO42-), while the SO42- formed on the KCS surface continuously provided Oads for the oxidation reaction. Over all, the study proposes a strategy for typical solid waste (CS) resource utilization, to attain simultaneous removal of NO and SO2 under low temperature conditions, thus achieving the goal of “treating waste with waste”.

Simultaneous Removal of NO and SO2 with a Novel Oxidation-Absorption Process Based on Air Microbubble Water System

Microbubbles (MBs) can spontaneously generate hydroxyl radicals (·OH) with high oxidizing capacity. In this study, a novel oxidation-absorption process based on a microbubble system in the indirect removal mode was proposed for the simultaneous removal of nitric oxide (NO) and sulfur dioxide (SO2). In this process, an air microbubble water system (AMBW) was produced by a microbubble generator (MBG) inhaling air and tap water and injected into an oxidation-absorption column reactor by the MBG, meanwhile the mixed gas composed of NO and SO2 passed through a micron-sized gas distributor at the bottom of the reactor and flowed into the AMBW. Important parameters including initial pH and temperature of tap water, operation time, NO concentration, SO2 concentration, and NaCl concentration were assessed to investigate the feasibility of the AMBW for the simultaneous removal of NO and SO2. The results showed that ·OH generated from the collapsed MBs played a critical role in the removal and the simultaneous removal of NO and SO2 was successfully achieved with the AMBW. Even with only tap water used as the absorbent, the removal efficiencies of NO and SO2 reached 92.7% and above 99%, respectively, when the experiment conditions were initial water pH 11.5, initial water temperature 298 K, 600 ppm NO, and 3,000 ppm SO2. Compared with the microbubble system in the direct removal mode, this new system is more suitable for the treatment of flue gases with low NO concentration and high volume. Moreover, this novel process should have a good prospect of industrial application in the flue gas treatment due to its high efficiencies of desulfurization and denitration and some advantages such as low usage cost of the reagents, simple system, and small occupation space.

An experimental study on the simultaneous removal of NO and SO2 with a new wet recycling process based on the micro-nano bubble water system.

The micronano bubble water system (MNBW) generated by a micronano bubble generator (MNBG) has the superior oxidation properties and can improve gas solubility. In the study, a new wet recycling process based on MNBW is proposed to simultaneously remove nitric oxide (NO) and sulfur dioxide (SO2). The important experimental parameters such as initial water pH, initial water temperature, NO and SO2 concentrations, and the presence of oxygen (O2) were investigated to explore the feasibility of desulfurization and denitration with MNBW. The experimental results showed that decreasing initial water pH or increasing initial water temperature and NO and SO2 concentrations were not conducive to the removal of NO or SO2. O2 could promote the removal of NO, but it had no effect on SO2 removal. In addition, SO2 removal efficiency always remained high and did not change obviously during the experimental period. However, NO removal efficiency gradually decreased in the first 50min and then became stable.

Simultaneous removal of nitric oxide and sulfur dioxide in a biofilter under micro-oxygen thermophilic conditions: Removal performance, competitive relationship and bacterial community structure

The efficiency of a biofilter to simultaneously remove nitric oxide (NO) and sulfur dioxide (SO2) was investigated under thermophilic (48 ± 2 °C) micro-oxygen (3 vol%) conditions. After the start-up stage (Days 0–14), the stable operation period was divided into three stages. SO2 inlet concentration remained 500 mg/m3, NO inlet concentrations were 300 mg/m3 (Days 15–40), 500 mg/m3 (Days 41–70) and 700 mg/m3 (Days 71–100). In each stable stage, the removal efficiency of NO and SO2 exceeded 90%, the maximum removal rates of NO and SO2 were 98.08% and 99.61%, respectively. The final products of SO2 were mostly sulphur. Nitrate-reducing bacteria inhibited sulphate-reducing bacteria. Illumina high-throughput sequencing confirmed that the relative abundance of nitrate-reducing bacteria was positively correlated with NO removal efficiency, the relative abundance of sulphate-reducing bacteria was related to the conversion rate of sulphur.

A study on simultaneous removal of NO and SO 2 by using sodium persulfate aqueous scrubbing

Abstract Nitric oxide (NO) removal and sulfur dioxide (SO2) removal by sodium persulfate (Na2S2O8) were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO2 removal are discussed. The effects of temperatures (35–90 °C), Na2S2O8 (0.05–0.5 mol·L− 1), FeSO4 (0.5–5.0 m mol·L− 1) and H2O2 (0.25 mol·L− 1) on NO and SO2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO2 was almost completely removed in the temperature range of 55–85 °C. Fe2 + accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol·L− 1 Na2S2O8 and 0.5–1.0 mmol·L− 1 Fe2 +, NO removal of 93.5%–99% was obtained at 75–90 °C, SO2 removal was higher than 99% at all temperatures. The addition of 0.25 mol·L− 1 H2O2 into 0.2 mol·L− 1 Na2S2O8 solution promoted NO removal efficiency apparently until utterly decomposition of H2O2, the SO2 removal was as high as 98.4% separately at 35 °C and 80 °C.

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

Fe and Co co-doped Mn-Ce/TiO2 (MCT) catalysts were investigated for the simultaneous removal of nitric oxide (NO) and elemental mercury (Hg0) at reaction temperature lower than 200 °C. The catalysts were characterized by Brunauer–Emmett–Teller (BET), temperature program reduction (TPR), scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The experimental results showed that the co-doped 2Fe4Co-MCT catalyst exhibited better performance for the simultaneous removal of NO and Hg0 compared to Fe or Co doped catalysts. This could be due to higher BET surface area and better redox property of 2Fe4Co-MCT catalyst. In addition, we propose that chemisorbed O2 played a dominant role in selective catalytic reduction (SCR) of NO while lattice O2 played a key role in Hg0 oxidation. The results also indicate that the introduction of Fe species enhanced the activity of SCR, whereas the introduction of Co species enhanced the oxidation of Hg0. The synergistic effect of Fe and Co species in the 2Fe4Co-MCT catalyst are also suggested to be an important mechanism for simultaneously removing NO and Hg0.

Catalytic Reduction of Hexaminecobalt(III) by Pitch‐based Spherical Activated Carbon (PBSAC)

AbstractThe wet ammonia (NH3) desulfurization process can be retrofitted to remove nitric oxide (NO) and sulfur dioxide (SO2) simultaneously by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexaminecobalt(II), Co(NH3), so that NO removal efficiency can be maintained at a high level for a long time. In this study, the catalytic performance of pitch‐based spherical activated carbon (PBSAC) in the simultaneous removal of NO and SO2 with this wet ammonia scrubbing process has been studied systematically. Experiments have been performed in a batch stirred cell to test the catalytic characteristics of PBSAC in the catalytic reduction of hexaminecobalt(III), Co(NH3). The experimental results show that PBSAC is a much better catalyst in the catalytic reduction of Co(NH3) than palm shell activated carbon (PSAC). The Co(NH3) reduction reaction rate increases with PBSAC when the PBSAC dose is below 7.5 g/L. The Co(NH3) reduction rate increases with its initial concentration. Best Co(NH3) conversion is gained at a pH range of 2.0–6.0. A high temperature is favorable to such reaction. The intrinsic activation energy of 51.00 kJ/mol for the Co(NH3) reduction catalyzed by PBSAC has been obtained. The experiments manifest that the simultaneous elimination of NO and SO2 by the hexaminecobalt solution coupled with catalytic regeneration of hexaminecobalt(II) can maintain a NO removal efficiency of 90% for a long time.

Nitric oxide reduction and carbon monoxide oxidation over carbon-supported copper-chromium catalysts

Carbon supported copper-chromium catalysts are shown to be very active for both the reduction of nitric oxide with carbon monoxide and the oxidation of carbon monoxide with oxygen. Mixed copper-chromium oxide active phases have good activity in the simultaneous removal of nitric oxide and carbon monoxide from exhaust gases. The influence of several catalyst variables has been investigated. The activity per volume of catalyst increases with increasing loading, while the intrinsic activity shows a maximum around C/M=100−50. An optimum catalyst for nitric oxide reduction and carbon monoxide oxidation has a copper/chromium ratio of 2/1. The apparent activation energy for the carbon monoxide oxidation over carbon supported copper-chromium catalysts is 77 kJ/mol, suggesting that the CuO bond rupture is the rate-limiting process. The reduction of nitric oxide takes place at higher temperatures. Since all catalysts have a low selectivity for molecular nitrogen formation at lower temperatures, the dissociation of nitric oxide is probably rate determining, resulting in a slightly reduced catalyst system. In an excess of carbon monoxide the reaction is first-order in nitric oxide and zero-order in carbon monoxide. Moisture inhibits the reaction by reversible competitive adsorption, whereas carbon dioxide does not. Oxygen completely inhibits the reduction of nitric oxide due to the more rapid reoxidation of the catalytic sites compared to nitric oxide. Therefore, the reduction of nitric oxide takes place only when all oxygen has been converted and, hence, is shifted to higher temperatures. As a possible consequence, the production of nitrous oxide is reduced. Nitric oxide and molecular oxygen react preferentially with carbon monoxide, so, in an excess of oxidizing component, gasification of the carbon support occurs at higher temperatures after carbon monoxide has been completely consumed.