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1.
Artigo em Inglês | MEDLINE | ID: mdl-32475209

RESUMO

Grilling restaurants are a major contributor to airborne particulate matter (PM) in metropolitan areas. In this study, the removal of PM during the grilling of pork belly using an orifice scrubber, which is a form of gas-induced spray scrubber, was assessed. During grilling, the particle mass concentration was the highest for 1.0 < PM ≤ 2.5 µm (55.5% of total PM emissions), followed by 0.5 < PM ≤ 1.0 (27.1%), PM ≤ 0.5 (10.7%), and PM > 2.5 µm (7.0%). The PM removal efficiency of the orifice scrubber at a gas flow of 4.5 m3 min-1 was > 99.7% for PM ≥ 2.5 µm, 89.4% for 1.0 < PM ≤ 2.5 µm, 62.1% for 0.5 < PM ≤ 1.0, and 36.5% for PM ≤ 0.5 µm. Although further research is necessary to optimize its use, the orifice scrubber offers a user-friendly technology for the control of PM in small grilling restaurants because of its simple design, uncomplicated operation, and satisfactory PM removal performance.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Poluição do Ar/prevenção & controle , Material Particulado/isolamento & purificação , Restaurantes , Gerenciamento de Resíduos/instrumentação , Animais , Culinária , Tamanho da Partícula , Carne Vermelha , República da Coreia , Suínos
2.
Chemosphere ; 253: 126684, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32464772

RESUMO

The use of Fusarium solani fungi in an expanded perlite packed biofilter was investigated for the treatment of a hexane polluted waste gas stream using selected ion flow tube mass spectrometry (SIFT-MS). The latter analytical technique proved to be of utmost importance to evaluate the performance of the biofilter at high time resolution (seconds) under various transient conditions, analogous to industrial situations. The biofilter was operational for 277 days with inlet loads varying between 1 and 14 g m-3 h-1 and applying an empty bed residence time of 116 s. The results showed a positive behaviour of the biofilter against different types of disruptions such as: (i) changes in the relative humidity of the inlet gas, (ii) stopping the carbon supply for 1, 5 and 10 days, (iii) varying the inlet hexane concentration (step increases and intermittent pulses) and (iv) limiting the availability of nutrients. X-ray imaging (both conventional 2D µCT and X-ray fluorescence, XRF) was applied for the first time on biofilter media in order to get insight in the internal structure of expanded perlite and to visualise the biomass growth. The latter in combination with online porosity measurements using SIFT-MS provides fundamental information regarding the biofiltration process.


Assuntos
Óxido de Alumínio , Poluentes Ambientais/isolamento & purificação , Filtração/métodos , Fungos , Hexanos/isolamento & purificação , Dióxido de Silício , Poluentes Atmosféricos/isolamento & purificação , Biodegradação Ambiental , Biomassa , Fusarium/crescimento & desenvolvimento , Fusarium/metabolismo , Análise Espectral/métodos
3.
Chemosphere ; 254: 126738, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32339799

RESUMO

Biofiltration is a typical air pollution control process for the treatment of volatile organic compounds (VOCs). Mass transfer of hydrophobic VOCs to the biofilm is limited which leads to low removal efficiency (RE). Aiming to enhance the transport of hydrophobic VOCs, the effect of hydrophobic fumed silica (HFS) addition to a biofilter (BF) for pentane removal was studied in this paper. The effect of HFS on pentane removal was evaluated by daily RE measurements and periodical headspace gas pentane pulse injections using SIFT-MS as analysis apparatus. The BF was operated during more than 100 days at an empty bed residence time (EBRT) of 120 s reaching an elimination capacity (EC) up to 93.8 g pentane m-3 h-1. At the last stage of the study, when a higher nutrient pulse and HFS to a concentration of 1.5% w/w wet were added, the BF showed better EC (46.3 ± 14.9 g pentane m-3 h-1; RE = 96.2%) compared to the previous stages (28.3 ± 4.4 g pentane m-3 h-1; RE = 68.3%). This overall performance improvement was in line with the short peak perturbation experiments carried out during the operational time which demonstrated, by net retention time (NRT) determination, to be a fast and reliable tool to gain insights into the behaviour of pollutants inside the BF and its state. Pentane demonstrated to have larger interactions with the packing material when HFS was added. NRT/EBRT ratio variated along the whole operational time, being larger at the last stage.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Filtração/métodos , Pentanos/isolamento & purificação , Dióxido de Silício/farmacologia , Compostos Orgânicos Voláteis/isolamento & purificação , Poluentes Atmosféricos/análise , Biodegradação Ambiental , Biofilmes , Filtração/instrumentação , Interações Hidrofóbicas e Hidrofílicas , Compostos Orgânicos Voláteis/análise
4.
Chemosphere ; 245: 125673, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31927491

RESUMO

Depletion of chloride from sea-salt aerosols affects their hygroscopicity, cloud condensation nuclei activity as well as microphysical and chemical properties of aerosols and clouds modifying earth-atmosphere radiative balance. Here, we proposed five possible reaction pathways through which the inorganic acids (H2SO4 and HNO3) could deplete chloride from sea-salt aerosols. We determined "maximum potential contribution" (MPC) of each acid and compared the MPC with actual chloride depletion. This step-by-step approach enables us to identify the most preferable reaction pathway(s) for coarse, superfine, accumulation and ultrafine aerosols over a Himalayan station (Darjeeling), a tropical urban station (Kolkata) and a tropical mangrove forest at the north-east coast of Bay of Bengal (Sundarban) in India. Over Kolkata and Darjeeling, locally generated acids reacted with transported sea-salts. Over Sundarban, the locally generated sea-salts from the Bay of Bengal reacted with the acids of biomass burning plume transported from Eastern Ghat and continental haze transported from upper Indo-Gangetic Plain. The average chloride depletion in PM10 ranged between 70 and 74% over Sundarban and 31-34% over Kolkata and Darjeeling. We observed that HNO3(g) depleted the larger (>1 µm) chlorides whereas H2SO4(g) depleted the smaller (<1 µm) chlorides over Kolkata and Darjeeling. However, in addition to H2SO4(g) and HNO3(g), some other species could be involved in chloride depletion over Sundarban mainly during winter. The study reveals that Sundarban acts as the major sink of the inorganic acids transported from Eastern Ghat biomass burning plume inhibiting their further advection towards inland regions.


Assuntos
Poluentes Atmosféricos/análise , Cloretos/isolamento & purificação , Monitoramento Ambiental/métodos , Clima Tropical , Áreas Alagadas , Aerossóis/análise , Poluentes Atmosféricos/isolamento & purificação , Altitude , Atmosfera/química , Biomassa , Índia , Tamanho da Partícula , Estações do Ano , Urbanização
5.
Environ Sci Pollut Res Int ; 27(2): 1598-1607, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31755062

RESUMO

The particulate matter (PM) could be simultaneously removed during the wet flue gas desulfurization (WFGD) process. To analyze the underlying mechanism and removal efficiency, the PM removal process in a desulfurization system was numerically simulated based on the population balance model and general dynamics equation in this study. The equation was solved using the fixed-step Monte Carlo method to determine the PM removal characteristics under different working conditions (such as spray intensity, velocity of the flue gas, and layers of slurry spray). When the flue gas velocity decreased from 7 to 3 m/s, the removal efficiency increased from 90.93 to 93.52%, and when the mean geometric droplet size decreased from 3 to 1 mm, the removal efficiency increased from 67.18 to 99.14%. Besides, large diameter PM was more easily removed by the desulfurization system. Thus, the numerical simulation method was proven to be feasible by comparing these results with field measurements of a WFGD system in a coal-fired power plant.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Gases , Material Particulado/isolamento & purificação , Centrais Elétricas , Carvão Mineral , Simulação por Computador
6.
J Chromatogr A ; 1612: 460646, 2020 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-31672268

RESUMO

A novel combined vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME)-micro-solid-phase extraction (µ-SPE) procedure for polycyclic aromatic hydrocarbons (PAHs) in ambient fine particulate matter of aerodynamic diameter of  ≤ 2.5 µm (PM2.5), was developed. PM2.5 was collected on polytetrafluoroethylene (PTFE)-coated glass fiber filter, that was first processed by ultrasonicating in aqueous solution. Then, VA-DLLME, followed by µ-SPE, were applied to the solution using 1-octanol and graphene oxide as extractant and sorbent, respectively for extracting the PAHs. The PAHs were determined by gas chromatography-tandem mass spectrometry (GC-MS/MS). Parameters affecting the extraction efficiency including selection of the sorbent, duration of DLLME and µ-SPE, desorption solvent type, and ultrasonication-assisted desorption time were investigated. Under the optimum extraction conditions, the method exhibited linear ranges of 0.5-50 µg/L and 0.5-100 µg/L depending on the analytes. The limits of detection were in the range of 0.013 µg/L-0.135 µg/L. The developed method was applied to determine the PAHs in genuine PM2.5 samples collected on PTFE glass fiber filters. The concentration levels in the atmospheric PM2.5 were determined to be from below the limit of quantification to 0.135 ng/m3. The relative recoveries obtained from spiked concentrations at 1 µg/L and 5 µg/L were in the range 57-88% with relative standard deviations <14%.


Assuntos
Poluentes Atmosféricos/análise , Cromatografia Gasosa-Espectrometria de Massas , Microextração em Fase Líquida/métodos , Material Particulado/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Microextração em Fase Sólida/métodos , Espectrometria de Massas em Tandem , Poluentes Atmosféricos/isolamento & purificação , Grafite , Limite de Detecção , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação
7.
Artigo em Inglês | MEDLINE | ID: mdl-31662034

RESUMO

Toluene is highly toxic and mutagenic, and it is generally used as an industrial solvent. Thus, toluene removal from air is necessary. To solve the problem of reducing high toluene concentrations with a short gas retention time (GRT), a quorum-sensing molecule [N-(3-oxododecanoyl)-L-homoserine lactone] (OHL) was added to a biotrickling filter (BTF). In this study, a BTF was used to treat synthetic and natural waste gases containing toluene. An extensive analysis was performed to understand the removal efficiency, removal characteristics, and bacterial community of the BTF. The addition of 20 µM OHL to the BTF significantly improved toluene removal, and more than 99.2% toluene removal was achieved at a GRT of 0.5 min when natural waste gas containing toluene (590-1020 ppm or 2.21-3.83 g m-3) was introduced. The maximum inlet load for toluene was 337.9 g m-3 h-1. Moreover, the BTF exhibited satisfactory adaptability to shock loading and shutdown operations. Pseudomonadaceae (33.0%) and Comamonadaceae (26.3%) were predominant bacteria in the system after a 98-day operation. These bacteria were responsible for toluene degradation. The optimal moisture content and low pressure drop for system operations demonstrated that the BTF was energy and cost efficient. Therefore, processing through a BTF with OHL is a favorable technique for toluene treatment.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Filtração/métodos , Microbiota , Percepção de Quorum , Tolueno/isolamento & purificação , 4-Butirolactona/análogos & derivados , 4-Butirolactona/metabolismo , Poluentes Atmosféricos/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/metabolismo , Biodegradação Ambiental , Reatores Biológicos/microbiologia , Filtração/instrumentação , Gases/isolamento & purificação , Gases/metabolismo , Homosserina/análogos & derivados , Homosserina/metabolismo , Microbiota/genética , Tolueno/metabolismo
8.
Inhal Toxicol ; 31(13-14): 446-456, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31874574

RESUMO

Objective: Stachybotrys chartarum is a hydrophilic fungal species commonly found as a contaminant in water-damaged building materials. Although several studies have suggested that S. chartarum exposure elicits a variety of adverse health effects, the ability to characterize the pulmonary immune responses to exposure is limited by delivery methods that do not replicate environmental exposure. This study aimed to develop a method of S. chartarum aerosolization to better model inhalation exposures. Materials and methods: An acoustical generator system (AGS) was previously developed and utilized to aerosolize and deliver fungal spores to mice housed in a multi-animal nose-only exposure chamber. In this study, methods for cultivating, heat-inactivating, and aerosolizing two macrocyclic trichothecene-producing strains of S. chartartum using the AGS are described. Results and discussion: In addition to conidia, acoustical generation of one strain of S. chartarum resulted in the aerosolization of fungal fragments (<2 µm aerodynamic diameter) derived from conidia, phialides, and hyphae that initially comprised 50% of the total fungal particle count but was reduced to less than 10% over the duration of aerosolization. Acoustical generation of heat-inactivated S. chartarum did not result in a similar level of fragmentation. Delivery of dry, unextracted S. chartarum using these aerosolization methods resulted in pulmonary inflammation and immune cell infiltration in mice inhaling viable, but not heat-inactivated S. chartarum. Conclusions: These methods of S. chartarum growth and aerosolization allow for the delivery of fungal bioaerosols to rodents that may better simulate natural exposure within water-damaged indoor environments.


Assuntos
Microbiologia do Ar/normas , Poluentes Atmosféricos/isolamento & purificação , Exposição por Inalação/análise , Pulmão/microbiologia , Stachybotrys/isolamento & purificação , Aerossóis , Animais , Líquido da Lavagem Broncoalveolar/microbiologia , Feminino , Temperatura Alta , Pulmão/imunologia , Pulmão/patologia , Camundongos , Camundongos Endogâmicos , Viabilidade Microbiana , Oryza/microbiologia , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/isolamento & purificação , Esporos Fúngicos/metabolismo , Stachybotrys/crescimento & desenvolvimento , Stachybotrys/metabolismo , Tricotecenos/metabolismo
9.
Environ Sci Pollut Res Int ; 26(29): 29660-29668, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31402436

RESUMO

Alkali metal chlorides emitted from sintering flue gas are easily adsorbed on the surface of activated carbon (AC) in the purification process. In this paper, NaCl particles adsorbing onto AC were simulated by impregnation method, and the size and morphology of NaCl particles were similar to those of NaCl-PM10 emitted from sintering flue gas. With the adsorption of NaCl particles, 2-10-µm pores of AC were filled, and the specific surface area of AC decreased. But NaCl led to the increase of acidic functional groups on the surface of AC. When 0.75 wt% NaCl was adsorbed, it was beneficial for AC catalytic denitration (de-NOx), because the chemical reaction was strengthened by acidic functional groups, so it showed a certain promotion of de-NOx efficiency. As 1.5 wt% NaCl and 3 wt% NaCl were adsorbed, NaCl had an inhibitory effect on AC de-NOx, which was because the specific surface area of AC decreased, and the prevention of physical adsorption played a major role. As a result, the de-NOx efficiency of AC adsorbed with 3 wt% NaCl decreased from 40.59 to 23.02% at 150 °C. Therefore, the absorption of NaCl fine particles on AC should not exceed 0.75 wt%.


Assuntos
Poluentes Atmosféricos/química , Carvão Vegetal/química , Gases/química , Cloreto de Sódio/química , Adsorção , Poluentes Atmosféricos/isolamento & purificação , Catálise , Resíduos Industriais , Óxido Nítrico/química , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
10.
Chemosphere ; 237: 124462, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31394446

RESUMO

Particulate matter and volatile organic compounds have emerged as a prime environmental concern with increasing air pollution in metropolitan cities leading to lung and heart-related issues. This paper describes a facile and novel method for fabrication of polyester based air filter via surface coating with Sericin for imparting effective removal of particulate matter and volatile organic compounds. A simple dip-coating method followed by thermal fixation has been adopted to coat Sericin on the polyester fiber. The developed changes in surface functionality and morphology of the polyester fiber were confirmed by Attenuated total reflection Fourier-transform infrared spectroscopy and Field emission scanning electron microscopy analysis. The fabricated air filter was tested for removal of particulate matter (generated burning incense stick) and volatile organic compounds (generated vaporizing gasoline), in an indoor chamber. The Sericin coated filter was able to remove the PM2.5 and PM 10 (from 1000 µg/m3 level to 5 µg/m3 in a 6.28 m3 chamber) within 27 and 23 min of operation, respectively. The fabricated filter very effectively removed particulate matter for 2160 cycles with intermittent washing. The Sericin-coated air filter also proved very effective for removal of volatile organic compounds (Benzene, Toluene, Ethylbenzene and Xylene) from an indoor chamber at a varying initial concentration of 100-1000 µg/m3. The adsorption behavior was described by Langmuir-Freundlich (sips) isotherm and pseudo-first order kinetics with minimal error. The maximum adsorption capacity (mg/g) obtained with Sips Isotherm fitting followed the order Xylene (6.97)>Ethyl Benzene (5.68)> Toluene (5.35) >Benzene (4.78).


Assuntos
Filtros de Ar , Poluição do Ar em Ambientes Fechados , Material Particulado/isolamento & purificação , Sericinas/química , Compostos Orgânicos Voláteis/isolamento & purificação , Adsorção , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/isolamento & purificação , Benzeno/análise , Benzeno/isolamento & purificação , Derivados de Benzeno/isolamento & purificação , Gasolina/análise , Microscopia Eletrônica de Varredura , Material Particulado/análise , Poliésteres/química , Espectroscopia de Infravermelho com Transformada de Fourier , Tolueno/análise , Compostos Orgânicos Voláteis/análise , Xilenos/análise , Xilenos/isolamento & purificação
11.
Indoor Air ; 29(6): 979-992, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31469187

RESUMO

The photocatalytic deactivation of volatile organic compounds and mold fungi using TiO2 modified with mono- and bimetallic (Pt, Cu, Ag) particles is reported in this study. The mono- and bimetal-modified (Pt, Cu, Ag) titanium(IV) oxide photocatalysts were prepared by chemical reduction method and characterized using XRD, XPS, DR/UV-Vis, BET, and TEM analysis. The effect of incident light, type and content of mono- and bimetallic nanoparticles deposited on titanium(IV) oxide was studied. Photocatalytic activity of as-prepared nanocomposites was examined in the gas phase using LEDs array. High photocatalytic activity of Ag/Pt-TiO2 and Cu/Pt-TiO2 in the reaction of toluene degradation resulted from improved efficiency of interfacial charge transfer process, which was consistent with the fluorescence quenching effect revealed by photoluminescence (PL) emission spectra. The photocatalytic deactivation of Penicillium chrysogenum, a pathogenic fungi present in the indoor environment, especially in a damp or water-damaged building using mono- and bimetal-modified (Pt, Cu, Ag) titanium(IV) oxide was evaluated for the first time. TiO2 modified with mono- and bimetallic NPs of Ag/Pt, Cu, and Ag deposited on TiO2 exhibited improved fungicidal activity under LEDs illumination than pure TiO2 .


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Fungos/isolamento & purificação , Nanocompostos/química , Óxidos , Compostos Orgânicos Voláteis/isolamento & purificação , Microbiologia do Ar , Poluição do Ar em Ambientes Fechados , Cobre , Platina , Prata , Titânio
12.
Sensors (Basel) ; 19(17)2019 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-31450808

RESUMO

Ammonia (NH3) emission is one of the major environmental issues in livestock farming. Gas measurements are required to study the emission process, to establish emission factors, and to assess the efficiency of emission reduction techniques. However, the current methods for acquiring reference measurements of NH3 are either high in cost or labor intensive. In this study, a cost-effective ammonia monitoring system (AMS) was constructed from a commercially-available gas analyzing module based on tunable diode laser absorption (TDLA) spectroscopy. To cope with the negative measurement biases caused by differing inlet pressures, a set of correction equations was formulated. Field validation of the AMS on NH3 measurement was conducted in a fattening pig barn, where the system was compared to a Fourier-transform infrared (FTIR) spectroscopy analyzer. Under two test conditions in a fattening pig barn, the absolute error of the AMS measurements with respect to the average obtained values between the AMS and the FTIR was respectively 0.66 and 0.08 ppmv, corresponding to 5.9% and 0.5% relative error. Potential sources of the measurement uncertainties in both the AMS and FTIR were discussed. The test results demonstrated that the AMS was capable of performing high-quality measurement with sub-ppm accuracy, making it a promising cost-effective tool for establishing NH3 emission factors and studying NH3 emission processes in pig houses.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Amônia/isolamento & purificação , Monitoramento Ambiental , Agricultura , Poluentes Atmosféricos/química , Amônia/química , Animais , Gado , Análise Espectral , Suínos
13.
Indoor Air ; 29(6): 943-955, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31444988

RESUMO

Removing benzene from indoor space plays an important role in indoor air purification. A novel filter with vegetal fiber paper (VFP) as matrix hosting silica gel is proposed in this paper for benzene removal. In order to investigate the feasibility and performance of this idea, firstly, three pieces of VFP samples impregnated with different amounts of silica gel are fabricated and their benzene adsorption quantities are tested. The results show that three times is recommended as the optimal number for impregnating. The VFP sample impregnated with silica gel after the third impregnating exhibits commendable coating stability and good benzene adsorption performance. Additionally, at low relative pressure (Pb /Ps  ≤ 0.05), the experimental data of benzene adsorption isotherms fit well with the Langmuir model with R2 greater than 0.97. Then, two actual filters made of VFP impregnated with silica gel after the third impregnating were fabricated. It is found that the pressure drop of the actual filter is only 1200 Pa/m when the air velocity is 2 m/s. Besides, the one-pass efficiency of the filter can reach to 19.44%. It is expected that the silica gel coated on the filter can be modified to improve the purification performance of the filter.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Benzeno/isolamento & purificação , Papel , Proteínas de Plantas , Sílica Gel , Adsorção , Poluição do Ar em Ambientes Fechados , Estudos de Viabilidade
14.
Sensors (Basel) ; 19(17)2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31443346

RESUMO

Artefact conditions need to be continuously monitored to avoid degradation effects naturally caused by time and public exploitation in order to increase the value of cultural assets. In this way, the atmospheric analysis of both biological and chemical pollutants potentially present inside conservation environments represents valid support for the adoption of preventive conservation actions by evaluating periodically the presence of risk for the same artefacts. The aim of the present study was to analyze the fungal particles, potentially biodeteriogen, through aerobiological volumetric monitoring, particularly inside valuable historical, artistic, and cultural sites. Different exposition and conservation typologies of the artefacts with different flows of visitors were considered. The applied methodologies have furnished a reliable description of biological air pollution due to the presence of fungal spores-moreover, they have allowed for the prevention of risk situations and the measurement of their evolution in order to limit degradation processes. Through aerobiological monitoring, it was possible to provide important indications for interventions of prevention, conservation and restoration of cultural heritage in indoor environments.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Monitoramento Ambiental/métodos , Esporos Fúngicos/crescimento & desenvolvimento , Poluição do Ar/prevenção & controle , Fungos/crescimento & desenvolvimento , Humanos
15.
Phys Chem Chem Phys ; 21(35): 19226-19233, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31441492

RESUMO

As one of the main air pollutants, nitrogen oxides (NOx) have serious effects on human health and the environment. In our previous study, we found that Mn-MOF-74 shows excellent catalytic performance for the selective catalytic reduction (SCR) reaction with NH3 being the reductant (NH3-SCR) at low temperature. To obtain a further understanding of the NH3-SCR mechanism in Mn-MOF-74, in this paper, we investigated two important parts of the NH3-SCR process in Mn-MOF-74 using the density functional theory (DFT) method. On the one hand, the structural characteristics of two types of oxygen vacancies of Mn-MOF-74, namely carboxyl oxygen vacancies and hydroxyl oxygen vacancies, and their adsorption properties to reaction species were calculated. It was found that the oxygen vacancies not only activate the reaction species, but also promote the desorption of NO2 molecules from metal sites for the subsequent rapid SCR reactions. On the other hand, we studied the effect of H2O on the structural stability and catalytic performance of Mn-MOF-74. It was found that the interaction of Mn-O bonds was weakened by H2O. Therefore, the influence of H2O should be considered for the future design of MOF-based catalysts for the SCR process.


Assuntos
Teoria da Densidade Funcional , Estruturas Metalorgânicas/química , Oxigênio/química , Água/química , Poluentes Atmosféricos/química , Poluentes Atmosféricos/isolamento & purificação , Catálise , Óxidos de Nitrogênio/química , Óxidos de Nitrogênio/isolamento & purificação , Substâncias Redutoras/química
16.
Artigo em Inglês | MEDLINE | ID: mdl-31319616

RESUMO

This study examined the use of high dosages of ultraviolet germicidal irradiation (UVGI) (253.7 nm) to deal with various concentrations of air pollutants, such as formaldehyde (HCHO), total volatile organic compounds (TVOC), under various conditions of humidity. A number of irradiation methods were applied for various durations in field studies to examine the efficiency of removing HCHO, TVOC, bacteria, and fungi. The removal efficiency of air pollutants (HCHO and bacteria) through long-term exposure to UVGI appears to increase with time. The effects on TVOC and fungi concentration were insignificant in the first week; however, improvements were observed in the second week. No differences were observed regarding the removal of HCHO and TVOC among the various irradiation methods in this study; however significant differences were observed in the removal of bacteria and fungi.


Assuntos
Microbiologia do Ar , Poluentes Atmosféricos/isolamento & purificação , Poluição do Ar em Ambientes Fechados/prevenção & controle , Formaldeído/isolamento & purificação , Compostos Orgânicos Voláteis/isolamento & purificação , Aerossóis , Poluentes Atmosféricos/efeitos da radiação , Formaldeído/efeitos da radiação , Umidade , Fotólise , Raios Ultravioleta , Compostos Orgânicos Voláteis/efeitos da radiação
17.
BMC Biotechnol ; 19(1): 52, 2019 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-31345193

RESUMO

BACKGROUND: Packing materials is a critical design consideration when employing biological reactor to treat malodorous gases. The acidification of packing bed usually results in a significant drop in the removal efficiency. In the present study, a biotrickling filter (BTF2) packed with plastic balls in the upper layer and with lava rocks in the bottom layer, was proposed to mitigate the acidification. RESULTS: Results showed that using combined packing materials efficiently enhanced the removal performance of BTF2 when compared with BTF1, which was packed with sole lava rocks. Removal efficiencies of more than 92.5% on four sulfur compounds were achieved in BTF2. Average pH value in its bottom packing bed was about 4.86, significantly higher than that in BTF1 (2.85). Sulfate and elemental sulfur were observed to accumulate more in BTF1 than in BTF2. Analysis of principal coordinate analysis proved that structure of microbial communities in BTF2 changed less after the shutdown but more when the initial pH value was set at 5.5. Network analysis of significant co-occurrence patterns based on the correlations between microbial taxa revealed that BTF2 harbored more diverse microorganisms involving in the bio-oxidation of sulfur compounds and had more complex interactions between microbial species. CONCLUSIONS: Results confirmed that using combined packing materials effectively improved conditions for the growth of microorganisms. The robustness of reactor against acidification, adverse temperature and gas supply shutdown was greatly enhanced. These provided a theoretical basis for using mixed packing materials to improve removal performance.


Assuntos
Filtros de Ar/microbiologia , Reatores Biológicos/microbiologia , Microbiota , Compostos de Enxofre/isolamento & purificação , Compostos de Enxofre/metabolismo , Poluentes Atmosféricos/isolamento & purificação , Poluentes Atmosféricos/metabolismo , Biodegradação Ambiental , Filtração/instrumentação , Filtração/métodos , Oxirredução
18.
J Chromatogr A ; 1602: 74-82, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31176481

RESUMO

The purpose of this study was to develop a new method for the sampling and analysis of naphthalene (Nap) and phenanthrene (Phe) in air. XAD-2 sorbent was prepared with polyaniline (PANI) to increase its adsorption area. Thus, 22-gauge needles were packed with XAD-2/PANI sorbent for the extraction of Nap and Phe, and sampling of the analytes of interest. The compounds were dynamically sampled from the headspace of the flask in laboratory and then analyzed using a gas chromatography (GC) device equipped with flame ionization detector (FID). The needle trap device (NTD) with the proposed sorbent was more sensitive and accurate than the NIOSH 5515 method. The results showed that the optimal temperature and time for the desorption of the analytes were 350 °C and 8 min, respectively. The analytical parameters such as carryover effect, breakthrough volume, and storage time were examined. The repeatability of the method was determined to be 9.4-13.5% for Nap and 7.1-15.7% for Phe. The limits of detection (LOD) for the analytes were in the range 0.002 - 0.09 ng L-1, and the limits of quantitation (LOQ) were in the range 0.01- 0.23 ng L-1. It was also found that the NTD packed with XAD-2/PANI sorbent was a sensitive and cost-effective method, and offered a high accuracy for the sampling and analysis of PAHs in air.


Assuntos
Poluentes Atmosféricos/análise , Compostos de Anilina/química , Técnicas de Química Analítica/instrumentação , Naftalenos/análise , Fenantrenos/análise , Adsorção , Poluentes Atmosféricos/isolamento & purificação , Cromatografia Gasosa , Ionização de Chama , Limite de Detecção , Agulhas , Hidrocarbonetos Policíclicos Aromáticos/análise , Temperatura
19.
Environ Pollut ; 246: 932-944, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31159143

RESUMO

Urban green spaces have the potential to mitigate and regulate atmospheric pollution. However, existing studies have primarily focused on the adsorption effect of different plants on atmospheric particulate matter (PM), whereas the effect of green space on PM has not been adequately addressed. In this study, the effect of different urban green space structures and configurations on PM was investigated through the 3D computational fluid dynamics (CFD) model ENVI-met by treating the green space as a whole based on field monitoring, and at the same time, the regulatory effect of green space on PM was examined by integrating information about the forest stand, PM concentration, and meteorological factors. The results show that the green space primarily affected wind speed but had no significant effect on relative humidity, temperature, or wind direction (P > 0.05). The PM concentration was significantly positively correlated with the relative humidity (P < 0.01), significantly negatively correlated with temperature (P < 0.05), but not significantly correlated with wind speed and direction (P > 0.05). Comparison with the measured values reveals that the ENVI-met model well reflected the differences in PM concentrations between different green spaces and the effect of green space on PM. In different green space structures, the uniform-type structure performed rather poorly at purifying PM, the concave-shaped structure performed the best, and the purifying effectiveness of the incremental-type and convex-shaped structure of green space was higher in the rear region than in the front region; in contrast, the degressional-type green space structure was prone to cause aggregation of the PM in the middle region. Broadleaf and broadleaf mixed forests had a better purifying effectiveness on PM than did coniferous forests, mixed coniferous forests, and coniferous broadleaf mixed forests. The above results are of great significance for urban planning and maximizing the use of urban green space resources.


Assuntos
Poluentes Atmosféricos/análise , Simulação por Computador , Microclima , Modelos Teóricos , Material Particulado/análise , Poluentes Atmosféricos/isolamento & purificação , Planejamento de Cidades , Monitoramento Ambiental , Florestas , Conceitos Meteorológicos , Material Particulado/isolamento & purificação
20.
Chemosphere ; 234: 388-394, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31228841

RESUMO

The main aim of this work is to study gas-phase toluene removal in one- and two-liquid phase biotrickling filters (O/TLP-BTF) and model the BTF performance using artificial neural networks (ANNs). The TLP-BTF was operated for 60 d in the presence of silicone oil at empty bed residence times (EBRTs) of 120, 60, and 45 s, respectively, and toluene concentrations in the range of 0.9-3.1 g m-3. A t-test analysis indicated that increasing the silicone oil volume ratio from 5 to 10% v/v, did not significantly improve the TLP-BTF performance (p-value = 0.65 > 0.05). The results from ANN modeling showed that toluene removal was more negatively affected by the inlet concentration (casual index, CI = -5.63) due to the kinetic limitation. The CI values for inlet concentration (+4.01) and liquid trickling rate (-2.45) indicated that the diffusion-limited regime controlled the removal process in the OLP-BTF.


Assuntos
Filtração/métodos , Redes Neurais de Computação , Óleos de Silicone , Tolueno/isolamento & purificação , Poluentes Atmosféricos/isolamento & purificação , Gases , Cinética , Óleos de Silicone/química , Óleos de Silicone/farmacologia
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