Catalytic reduction of 4-nitrophenol by green silver nanocomposites assembled using microbial extracellular polymer substances

Two methods, diesel particulate filter (DPF) and selective catalytic reduction (SCR) systems, for controlling diesel emissions have become widely used, either independently or together, for meeting increasingly stringent emissions regulations world-wide. Each of these systems is designed for the reduction of primary pollutant emissions including particulate matter (PM) for the DPF and nitrogen oxides (NOx) for the SCR. However, there have been growing concerns regarding the secondary reactions that these aftertreatment systems may promote involving unregulated species emissions. This study was performed to gain an understanding of the effects that these aftertreatment systems may have on the emission levels of a wide spectrum of chemical species found in diesel engine exhaust. Samples were extracted using a source dilution sampling system designed to collect exhaust samples representative of real-world emissions. Testing was conducted on a heavy-duty diesel engine with no aftertreatment devices to establish a baseline measurement and also on the same engine equipped first with a DPF system and then a SCR system. Each of the samples was analyzed for a wide variety of chemical species, including elemental and organic carbon, metals, ions, n-alkanes, aldehydes, and polycyclic aromatic hydrocarbons, in addition to the primary pollutants, due to the potential risks they pose to the environment and public health. The results show that the DPF and SCR systems were capable of substantially reducing PM and NOx emissions, respectively. Further, each of the systems significantly reduced the emission levels of the unregulated chemical species, while the notable formation of new chemical species was not observed. It is expected that a combination of the two systems in some future engine applications would reduce both primary and secondary emissions significantly.

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Effect of Fe on the Selective Catalytic Reduction of NO by NH3 at Low Temperature over Mn/CeO2-TiO2 Catalyst

Journal of Inorganic Materials ◽

10.3724/sp.j.1077.2012.00495 ◽

2012 ◽

Vol 27 (5) ◽

pp. 495-500 ◽

Cited By ~ 7

Author(s):

Da-Wang WU ◽

Qiu-Lin ZHANG ◽

Tao LIN ◽

Mao-Chu GONG ◽

Yao-Qiang CHEN

Keyword(s):

Low Temperature ◽

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Reduction Of No

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Influence of Fe Content on Catalytic Reduction of N2O with CH4 over FeAlPO-5 Catalyst

CHINESE JOURNAL OF CATALYSIS (CHINESE VERSION) ◽

10.3724/sp.j.1088.2010.90601 ◽

2010 ◽

Vol 31 (1) ◽

pp. 68-71 ◽

Cited By ~ 1

Author(s):

Xiaoxu ZHAO ◽

Dang-guo CHENG ◽

Fengqiu CHEN ◽

Xiaoli ZHAN

Keyword(s):

Catalytic Reduction ◽

Fe Content

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Retention and expression of recombinant plasmids in suspended and biofilm-bound bacteria degrading trichloroethene (TCE)

Water Science & Technology ◽

10.2166/wst.1997.0346 ◽

1997 ◽

Vol 36 (10) ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

James D. Bryers ◽

Robert R. Sharp

Keyword(s):

Biofilm Reactor ◽

Bacterial Biofilm ◽

Laboratory Evaluation ◽

Recombinant Bacteria ◽

Suitable Host ◽

Term Operation ◽

Open Environment ◽

Recombinant Microorganisms ◽

Extracellular Polymer

Exposure of plasmid recombinant microorganisms to an open environment, either inadvertently or intentionally, requires research into those fundamental processes that govern plasmid retention, transfer and expression. In the open environment, a majority of the microbial activity occurs associated with an interface, within thin biological layers consisting of cells and their insoluble extracellular polymer, layers known as biofilms. Current toxic wastewater or wastegas treatment reactors exploit bacterial biofilm systems for certain system operating advantages. Using recombinant bacteria within a biofilm reactor to degrade xenobiotic wastes requires finding a suitable host to harbor and express the desired plasmid phenotype. Suitable host characteristics include: the ability to produce copious amounts of biofilm, resistance to waste-related injury and toxicity, and the ability to retain and express the desired plasmid during long term operation. This paper reports on a laboratory evaluation of factors governing plasmid retention and the expression of trichloroethene (TCE) degradative capacity in both suspended and biofilm cultures.

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Surface charge and extracellular polymer of sludge in the anaerobic degradation process

Water Science & Technology ◽

10.2166/wst.1996.0565 ◽

1996 ◽

Vol 34 (5-6) ◽

pp. 309-316 ◽

Cited By ~ 20

Author(s):

X. S. Jia ◽

Herbert H. P. Fang ◽

H. Furumai

Keyword(s):

Surface Charge ◽

Growth Phase ◽

Anaerobic Degradation ◽

Degradation Process ◽

Anaerobic Sludge ◽

Batch Experiments ◽

High Substrate Concentration ◽

Negative Surface ◽

Negative Surface Charge ◽

Extracellular Polymer

Changes of surface charge and extracellular polymer (ECP) content were investigated in batch experiments for three anaerobic sludges, each of which had been enriched at 35°C and pH 639-7.3 for more than 40 batches using propionate, butyrate and glucose, individually, as the sole substrate. Results showed that both ECP and the negative surface charge were dependent on the growth phase of microorganisms. They increased at the beginning of all batches when the microorganisms were in the prolific-growth phase, having high substrate concentration and food-to-microorganisms ratio. Both later gradually returned to their initial levels when the microorganisms were in the declined-growth phase, as the substrate became depleted. The negative surface charge increased linearly with the total-ECP content in all series with slopes of 0.0187, 0.0212 and 0.0157 meq/mg-total-ECP for sludge degrading propionate, butyrate and glucose, respectively. The change of surface charge for the first two sludges was mainly due to the increase of proteinaceous fraction of ECP; but, for glucose-degrading sludge, that could be due to the increases of both proteinaceous and carbohydrate fractions of ECP. The negative-charged nature of anaerobic sludge implies that cations should be able to promote granulation of anaerobic sludge.

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Aplicação de Multi-Layer Perceptron para Previsão de Emissão de Gases derivados de Veículos a Diesel

Latin American Journal of Energy Research ◽

10.21712/lajer.2016.v3.n2.p1-11 ◽

2017 ◽

Vol 3 (2) ◽

pp. 1-11

Author(s):

Luís Otávio Rigo Jr. ◽

Jesuina Cássia Santiago de Araújo ◽

Leandro Nogueira dos Santos ◽

Mona Lisa Moura de Oliveira

Keyword(s):

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Back Propagation ◽

Multi Layer Perceptron

Fontes veiculares movidos a Diesel têm contribuido significativamente para o aumento da poluição atmosférica. A tendência mundial de utilizar motor Diesel se deve ao rendimento real alcançado por esta máquina (~34%), quando comparada com motores Otto (~26%). Em termos de poluição, tais motores apresentam a vantagem de emitir menor concentração de hidrocarbonetos e CO2. Por outro lado, o motor Diesel apresenta a desvantagem de emitir materiais particulados e NOx. Com fins de atender a legislação, tem sido incorporado aos veículos a Diesel um sistema catalítico, que injeta uréia nos gases de escape. Tal processo, conhecido como SCR (Selective Catalytic Reduction), tem por finalidade transformar NOx em N2 e H2O. Órgãos governamentais têm atuado como agentes controladores, exigindo dos fabricantes de motores soluções tecnológicas, capazes de reduzir os níveis de emissões destes poluentes. Essas soluções estão atreladas a uma série de testes experimentais onerosos. Tendo-se em vista que as taxas de emissão de NOx dependem de fatores que se correlacionam de forma complexa, faz-se necessário à utilização de ferramentas de simulação para prever tais taxas. Neste trabalho, foi utilizada uma Rede Neural Artificial, denominada Multi-Layer Perceptron, com algoritmo de aprendizado supervisionado Back Propagation, para estimar as taxas de emissão dos gases NOx, NH3 e N2O em veículos a Diesel. Os resultados mostraram que parâmetros de entrada (velocidade espacial, temperatura, concentração de NOx, de NH3, de O2 , de SO2 e de H2O) se correcionam fortemente com as taxas de emissão de NOx e NH3 na saída. Este fator foi comprovado pela grande capacidade de aprendizado das redes testadas, com erro médio próximo de 0,01 no conjunto de aprendizado. Os resultados sobre o conjunto de teste demonstraram, também, grande capacidade de generalização das redes. O melhor resultado encontrado foi de 2,9% para NOx e NH3 e de N2O de 5,1%. Estes resultados revelam que a RNA demonstrou ser um método eficiente para prever as taxas de emissão de poluentes em perímetro urbano e rodovias.

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Facile Synthesis of Cu2O nanoparticle-loaded Carbon Nanotubes Composite Catalysts for Reduction of 4-Nitrophenol

Current Nanoscience ◽

10.2174/1573413715666191206161555 ◽

2020 ◽

Vol 16 (4) ◽

pp. 617-624 ◽

Cited By ~ 12

Author(s):

Yao Feng ◽

Ran Wang ◽

Juanjuan Yin ◽

Fangke Zhan ◽

Kaiyue Chen ◽

...

Keyword(s):

Carbon Nanotubes ◽

Mechanical Stability ◽

Catalytic Reduction ◽

High Surface ◽

High Surface Area ◽

Reduction Reaction ◽

Cycle Performance ◽

Simple Method ◽

Composite Catalysts ◽

Cu2o Nanoparticles

Background: 4-nitrophenol (4-NP) is one of the pollutants in sewage and harmful to human health and the environment. Cu is a non-noble metal with catalytic reduction effect on nitro compounds, and.has the advantages of simple preparation, abundant reserves, and low price. Carbon nanotubes (CNT) are widely used for substrate due to their excellent mechanical stability and high surface area. In this study, a simple method to prepare CNT-Cu2O by controlling different reaction time was reported. The prepared nanocomposites were used to catalyze 4-NP. Methods: CNTs and CuCl2 solution were put into a beaker, and then ascorbic acid and NaOH were added while continuously stirring. The reaction was carried out for a sufficiently long period of time at 60°C. The prepared samples were dried in a vacuum at 50°C for 48 h after washing with ethyl alcohol and deionized water. Results: Nanostructures of these composites were characterized by scanning electron microscope and transmission electron microscopy techniques, and the results at a magnification of 200 nanometers showed that Cu2O was distributed on the surface of the CNTs. In addition, X-ray diffraction was performed to further confirm the formation of Cu2O nanoparticles. The results of ultraviolet spectrophotometry showed that the catalytic effect of the compound on 4-NP was obvious. Conclusions: CNTs acted as a huge template for loading Cu2O nanoparticles, which could improve the stability and cycle performance of Cu2O. The formation of nanoparticles was greatly affected by temperature and the appropriate concentration, showing great reducibility for the 4-NP reduction reaction.

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