• Parasites, Hosts and Diseases
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• v.61 no.4
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• pp.388-396
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• 2023

Entamoeba histolytica is an enteric tissue-invasive protozoan parasite causing amoebic colitis and liver abscesses in humans. Amoebic contact with host cells activates intracellular signaling pathways that lead to host cell death via generation of caspase-3, calpain, Ca²⁺ elevation, and reactive oxygen species (ROS). We previously reported that various NADPH oxidases (NOXs) are responsible for ROS-dependent death of various host cells induced by amoeba. In the present study, we investigated the specific NOX isoform involved in ROS-dependent death of hepatocytes induced by amoebas. Co-incubation of hepatoma HepG2 cells with live amoebic trophozoites resulted in remarkably increased DNA fragmentation compared to cells incubated with medium alone. HepG2 cells that adhered to amoebic trophozoites showed strong dichlorodihydrofluorescein diacetate (DCF-DA) fluorescence, suggesting intracellular ROS accumulation within host cells stimulated by amoebic trophozoites. Pretreatment of HepG2 cells with the general NOX inhibitor DPI or NOX2-specific inhibitor GSK 2795039 reduced Entamoeba-induced ROS generation. Similarly, Entamoeba-induced LDH release from HepG2 cells was effectively inhibited by pretreatment with DPI or GSK 2795039. In NOX2-silenced HepG2 cells, Entamoeba-induced LDH release was also significantly inhibited compared with controls. Taken together, the results support an important role of NOX2-derived ROS in hepatocyte death induced by E. histolytica.

• Clean Technology
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• v.21 no.2
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• pp.117-123
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• 2015

This inquiry was conducted to develop DeNOx catalyst for LNT. In order to develop appropriate catalysts, four catalysts, which do not use PGM (Platinum Group Metal), were carefully selected : Al/Co/Mn, Al/Co/Ni/Mn, Al/Co/Mn/Ca, Al/Co/Ni mixed metal oxides during preliminary experiments. Also, XRD, EDS, SEM, BET and TPD tests were carried as well to evaluate both physicochemical properties of such four catalysts. As a result of the experiment, four catalysts were composed of spinel-shaped crystals and had more than enough pore volume and size to have oxidation-reduction reaction of NOx gases. Additionally, through TPD test, all four types of catalysts were proved to possibly have an oxidation-reduction acid site and NO oxidation activities similar to commercial catalysts. Based on the results above, if we have further change in the composition components and active ingredients according to the catalysts that were chosen in this investigation, then we are more welcomed to expect to have an enhanced DeNox catalyst for LNT.

• Journal of Environmental Science International
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• v.12 no.1
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• pp.47-54
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• 2003

This paper have examined the optimum combination of SNCR and SCR by varying SNCR injection temperature and NSR ratio along with SCR space velocity. NOx reduction experiments using a SNCR/SCR combined process have been conducted in simple NO/NH$_3$/O$_2$ gas mixtures. Total gas flow rate was kept constant 4 liter/min throughout the SNCR and SCR reactors, where initial NOx concentration was 500 ppm in the presence of 5% O$_2$. Commercial catalyst, sulfated V$_2$O$\_$5/-WO$_3$/TiO$_2$, was used for SCR NOx reduction. The residence time and space velocity were around 1.67 sec, 2,400 h$\^$-1/ and 6,000 h$\^$-1/ in the SNCR and SCR reactors, respectively. SNCR NOx reduction effectively occurred in a temperature window of 900-950$^{\circ}C$. About 88% NOx reduction was achieved with an optimum temperature of 950$^{\circ}C$ and NSR=1.5. SCR NOx reduction using commercial V$_2$O$\_$5/-WO$_3$-SO$_4$/TiO$_2$ catalyst occurred in a temperature window of 200-450$^{\circ}C$ 80-98% NOxreduction was possible with SV=2400 h$\^$-1/ and a molar ratio of 1.0-2.0. A SNCR/SCR(SV=6000 h$\^$-1/) combined process has shown same NOx reduction compared with a stand-alone SCR(SV=2400 h$\^$-1/) unit process of 98% NOx reduction. The NH$_3$-based chemical could routinely achieve SNCR/SCR combined process total NOx reductions of 98% with less than 5 ppm NH$_3$ slip at NSR ranging from about 1.5 to 2.0, SNCR temperature of 900$^{\circ}C$-950$^{\circ}C$, and SCR space velocity of 6000 h$\^$-1/. Particularly, more than 98% NOx reduction was possible using the combined process under the conditions of T$\_$SNCR/=950$^{\circ}C$, T$\_$SCR/=350$^{\circ}C$, 5% O$_2$, SV=6000 h$\^$-1/ and NH$_3$/NOx=1.5. A catalyst volume was about three times reduced by SNCR/SCR combined process compared with SCR process under the same controlled conditions.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.855-861
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• 2013

Small-pore Cu-chabazite SCR catalysts with high NOx conversion at low temperatures are of interest for marine diesel engines with exhaust temperatures in the range of 150 to $300^{\circ}C$. Unfortunately, fuels for marine diesel engines can contain a high level of sulfur of up to 1.5% by volume, which corresponds to a $SO_2$ level of 500 ppm in the exhaust gases for an engine operating with an A/F ratio of 50:1. This high level of $SO_2$ in the exhaust may have detrimental effects on the NOx performance of the Cu-chabazite SCR catalysts. In the present study, a bench-flow reactor is used to investigate the effects of sulfur poisoning on the NOx performance of Cu-chabazite SCR catalysts. The SCR catalysts were exposed to simulated diesel exhaust gas stream consisted of 500 ppm $SO_2$, 5% $CO_2$, 14% $O_2$, 5% $H_2O$ with $N_2$ as the balance gas at 150, 200, 250 and $300^{\circ}C$ for 2 hours at a GHSV of 30,000 $h^{-1}$. After sulfur poisoning the low-temperature NOx performance of the SCR catalyst is evaluated over a temperature range of 150-$300^{\circ}C$ to determine the extent of the catalyst deactivation. Desulfation is also carried out at 600 and $700^{\circ}C$ for 30 minutes to determine whether it is possible to recover the NOx performance of the sulfur-poisoned SCR Catalysts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.696-701
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• 2018

The nitrogen oxides generated during combustion reactions have a great influence on the generation of acid rain and fine dust. As an NOx reduction method, exhaust gas recirculation combustion using Coanda nozzles capable of recirculating a large amount of exhaust gas with a small amount of air has recently been utilized. In this study, for the burner outlet with dual end opening, the use of a recirculation burner was investigated for the distribution of the pressure, streamline, temperature, combustion reaction rate and nitrogen oxides using computational fluid analysis. The gas mixed with the combustion air and the recirculated exhaust gas flow in the tangential direction of the circular cylinder burner, so that there is a region with low pressure in the vicinity of the fuel nozzle exit. As a result, a reverse flow is formed in the central portion of the burner near the center of the circular cylinder burner and the exhaust gas is discharged to the outside region of the circular cylinder burner. The combustion reaction occurs on the right side of the burner and the temperature and NOx distribution are relatively higher than those on the left side of the burner. It was found that the average NOx production decreased from an air flow ratio of 1.0 to 1.5. When the air flow ratio is 1.8, the NOx production increases abruptly. It is considered that the NOx production reaction increases exponentially with temperature when the air ratio is more than 1.5 and the NOx production reaction rate increases rapidly on the right-hand side of the burner.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.671-678
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• 2000

Reaction characteristics of simultaneous removal of SOx and NOx have been investigated in a thermogravimetric analyzer and tubular fixed bed reactor using the $CuO/{\gamma}-Al_2O_3$ sorbent/catalyst. Sulfur removal capacity of $CuO/{\gamma}-Al_2O_3$ sorbent/catalyst is largely enhanced above both the temperature of $450^{\circ}C$ and the loading of 6wt% due to the participation of alumina support in a sulfation reaction. The NO reduction efficiency of 8wt% $CuO/{\gamma}-Al_2O_3$ sorbent/catalyst shows the maximum value at $370^{\circ}C$ and then decreases with the increase of reaction temperature due to the oxidation of $NH_3$ gas. The presence of sulfate on the surface of sorbent/catalyst enhances the optimum reaction temperature showing the maximum deNOx efficiency. In the simultaneous removal of SOx and NOx at $250^{\circ}C$. deNOx activity of $CuO/{\gamma}-Al_2O_3$ sorbent/catalyst is rapidly decreased due to the formation of ammonium salts such as $NH_4HSO_4$. In the simultaneous removal reaction of SOx and NOx, the optimum temperature showing the maximum deNOx efficiency increases to $400^{\circ}C$ due to the presence of $SO_2$ gas.

• Journal of the Korean Applied Science and Technology
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• v.36 no.2
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• pp.668-675
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• 2019

Fine dust in air pollutants is recognized as one of the most serious social environmental problems. Most of the NOx is generated in a combustion process such as that of a coal-fired power plant, and therefore efficient elimination of the NOx from the coal-fired power plants is needed. This study investigates the removal efficiency of using $TiO_2$, a photocatalyst, to remove NOx by Selective Catalytic Reduction (SCR). To evaluate the NOx removal efficiency, $TiO_2$ catalyst and phosphate binder were mixed on the surface of the $Al_2O_3$ substrate with the exothermic agent, and the substrate was heat-treated. The NOx removal efficiency of the catalysts was evaluated according to the temperature, and XRD, SEM, TG-DTA and BET analyzes were performed to investigate the physicochemical properties of the catalysts. NOx removal efficiency was 58.7%~65.9% at 20min, 63.7~66.0% at 30min with temperature change according to time($250^{\circ}C{\sim}500^{\circ}C$). The $TiO_2$ used in the SCR for NOx removal is judged to have the most efficient removal efficiency at $300^{\circ}C$.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.506-513
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• 2020

In this study, the mechanical properties, absorption, and reduction performance of NOx in the mortar containing mineral admixture like zeolite and active hwangtoh were evaluated. Zeolite and active hwangtoh were used as binder, and zeolite and active hwangtoh were substituted for cement. The substitution ratio of two types of mineral admixtures was considered as 20 and 30% respectively. As a result of evaluating the compressive strength and flexural strength of each mortar specimen, the highest strength in the plain mixture was evaluated. As the substitution ratio of zeolite and active hwangtoh increased, the compressive and flexural strength decreased. In addition, the difference of compressive and flexural strength between active hwangtoh and zeolite mixing was evaluated to be insignificant. To evaluate the absorption rate, the mixture was designed to lower the W/B ratio of the existing mixture and set the substitution ratio of active hwangtoh and zeolite at 25%. The highest absorption ratio in the mortar with zeolite was evaluated, and the difference in absorption ratio between the remaining two mortar mixtures was small. The assessment of reduction performance of NOx considering the application of photocatalyst showed a clearly decreasing reduction behavior, even if they were the same mortar mixture. Zeolite and active hwangtoh also showed a higher NOx reduction than the Plain mixture, because of their porosity properties. In the case of active hwangtoh, the absorption ratio was lower than that of zeolite mixture, but the reduction of NOx performance was better than the result of zeolite mixture.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.05a
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• pp.38-40
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• 2003

본 연구에서 적용한 저 NOx 연소법의 NOx 저감 효과를 비교해 보면 다단 연소법이 지연연소 효과와 국부적인 최고 화염온도 감소, 고온부에서의 산소농도 감소효과 등이 동시에 나타나 저 과잉공기 연소법, 배기가스 재순환법, 이단 연소법 보다 더 큰 NOx 저감효과를 얻을 수 있음을 알 수 있었다. 다만, 총 공급공기 량에 대한 분할 공급공기량의 비가 일정수준 이상으로 커지면 CO 발생량 증가로 효율저하 등의 문제점이 우려되므로 연소상태를 저하시키지 않는 공급비를 산정하는 것이 중요할 것으로 생각된다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2000.11a
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• pp.229-232
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• 2000

산업 현장에서 연소 과정중 발생되는 NOx를 제거하기 위한 방법으로 현재 연구 및 상업 화 대상에서 가장 널리 사용되고 있는 것이 SCR(Selective Catalytic Reduction)과 SNCR((Selective non-catalytic reduction)이다. 그러나, SCR의 경우 높은 장치비와 유지비 가 소요되어, 최근에는 로 내에 요소용액을 직접 분사하여 NOx를 질소와 수증기로 환원시켜 제거하는 방법인 SNCR에 대한 연구가 활발히 진행되고 있는 추세이다.(중략)