The recently developed Reynolds mass flux (RMF) model is applied to simulate the reactive flow in a gas-particle bubbling fluidized bed (BFB). By using this model, the profiles of species/particles ...concentration and phase velocities are able to be predicted. The proposed model avoids the generalized Boussinesq’s postulation, thereby realizing the simulation of anisotropic mass transfer. The simulations are validated by experiments for ozone decomposition in a gas-particle bubbling fluidized bed and satisfactory agreement is found between them. Furthermore, the proposed model successfully characterizes the anisotropy of turbulent mass diffusivity in gas-particle BFB.
•We investigated the reaction of paracetamol with ozone and hydroxyl radicals at pH 7.2 and 5 respectively.•Rate constants were determined and reaction kinetic was discussed.•The degradation of ...paracetamol by ozone and hydroxyl radicals was modelled in real water conditions.•Ozonation transformation products were studied and reaction pathways were proposed.•Acute toxicity of the ozonated solutions was monitored by means of Vibrio fisheri assay.
Paracetamol oxidation by ozonation and H2O2/UV processes was investigated. The second-order rate constant for the reaction of paracetamol with ozone was determined at pH 7.2 (kO3/PRC=2.57×106M-1s-1). The rate constant of the elementary reaction of ozone with the ionized form of PRC was then calculated and the pH dependence of the ozonation reaction of PRC was estimated. The second-order rate constant of the reaction of paracetamol with HO radicals was also determined at pH 5 through the H2O2/UV oxidation system (kHO/PRC=4.94×109M-1s-1). In the light of the high rate constants obtained, two conclusions on the kinetics of paracetamol ozonation in real water were drawn: (i) hydroxyl radicals do not have any impact on the removal of paracetamol during ozonation of real waters; (ii) a half-life of 0.03 s can be estimated for paracetamol, for a residual ozone concentration of 0.4mgL−1. Hydroquinone and two other ozonation transformation products were identified by LC/UV, LC/MS and MS/MS analyses. In parallel, for the first time, toxicity was measured in ozonated paracetamol solutions with the luminescent bacteria Vibrio fisheri test. The results showed an increase in toxicity as paracetamol degraded. This toxicity could not be assigned to hydroquinone formation only. One or several other transformation products more toxic than paracetamol might be formed.
Biomass fires impact global atmospheric chemistry. The reactive compounds emitted and formed due to biomass fires drive ozone and organic aerosol formation, affecting both air quality and climate. ...Direct hydroxyl (OH) Reactivity measurements quantify total gaseous reactive pollutant loadings and comparison with measured compounds yields the fraction of unmeasured compounds. Here, we quantified the magnitude and composition of total OH reactivity in the north-west Indo-Gangetic Plain. More than 120% increase occurred in total OH reactivity (28 s
to 64 s
) and from no missing OH reactivity in the normal summertime air, the missing OH reactivity fraction increased to ~40 % in the post-harvest summertime period influenced by large scale biomass fires highlighting presence of unmeasured compounds. Increased missing OH reactivity between the two summertime periods was associated with increased concentrations of compounds with strong photochemical source such as acetaldehyde, acetone, hydroxyacetone, nitromethane, amides, isocyanic acid and primary emissions of acetonitrile and aromatic compounds. Currently even the most detailed state-of-the art atmospheric chemistry models exclude formamide, acetamide, nitromethane and isocyanic acid and their highly reactive precursor alkylamines (e.g. methylamine, ethylamine, dimethylamine, trimethylamine). For improved understanding of atmospheric chemistry-air quality-climate feedbacks in biomass-fire impacted atmospheric environments, future studies should include these compounds.
The ozone monitoring instrument Levelt, P.F.; van den Oord, G.H.J.; Dobber, M.R. ...
IEEE transactions on geoscience and remote sensing,
05/2006, Letnik:
44, Številka:
5
Journal Article
Recenzirano
The Ozone Monitoring Instrument (OMI) flies on the National Aeronautics and Space Administration's Earth Observing System Aura satellite launched in July 2004. OMI is a ultraviolet/visible (UV/VIS) ...nadir solar backscatter spectrometer, which provides nearly global coverage in one day with a spatial resolution of 13 km/spl times/24 km. Trace gases measured include O/sub 3/, NO/sub 2/, SO/sub 2/, HCHO, BrO, and OClO. In addition, OMI will measure aerosol characteristics, cloud top heights, and UV irradiance at the surface. OMI's unique capabilities for measuring important trace gases with a small footprint and daily global coverage will be a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change. OMI's high spatial resolution is unprecedented and will enable detection of air pollution on urban scale resolution. In this paper, the instrument and its performance will be discussed.
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•O3 sensors were employed in the development of a miniaturised O3 measurement device combined with LabJack and Labview data acquisition.•The O3 sensor device was firstly applied in ...the laboratory experiment and also in air quality monitoring.•The influences relative humidity and gas flow rate on sensor signals were investigated independently.
Ozone (O3) measurements are a critical component of air quality management and many atmospheric chemistry laboratory experiments. Conventional ozone monitoring devices based on UV absorption are relatively cumbersome and expensive, and have a relative high power consumption that limits their use to fixed sites. In this study electrochemical O3 sensors (OXB421, Alphasense) were used in a miniaturised O3 measurement device combined with LabJack and Labview data acquisition (DAQ). The device required a power supply of 5V direct current (VDC) with a total power consumption of approximately 5W. Total weight was less than 0.5kg, low enough for portable in situ field deployment. The electrochemical O3 sensors produced a voltage signal positively proportional to O3 concentrations over the range of 5ppb–10ppm. There was excellent agreement between the performances of two O3 sensors with a good linear coefficient (R2=0.9995). The influences of relative humidity (RH) and gas sample flow rate on sensor calibrations and sensitivities have been investigated separately. Coincident calibration curves indicate that sensor performances were almost identical even at different RHs and flow rates after a re-zeroing process to offset the sensor baseline drifts. Rapid RH changes (∼20%/min) generate significant and instant changes in sensor signal, and the sensors consistently take up to 40min to recover their original values after such a rapid RH change. In contrast, slow RH changes (∼0.1%/min) had little effect on sensor response. To test the performance of the miniaturised O3 device for real-world applications, the O3 sensors were employed for (i) laboratory experiments to measure O3 loss by seawater uptake and (ii) air quality monitoring over an 18-day period. It was found that ozone uptake by seawater was linear to the volume of linoleic acid on a sea surface microlayer and the calculated uptake coefficients based on sensor measurements were close to those from previous studies. For the 18-day period of air quality monitoring the corrected data from the O3 sensor was in a good agreement with those obtained by reference UV O3 analyser with an r2 of 0.83 (n=8502). The novelty of this study is that the electrochemical O3 sensor was comprehensively investigated in O3 measurements in both laboratory and ambient air quality monitoring and it can to be a miniaturised alternative for conventional O3 monitoring devices due to its low cost, low power-consumption, portable and simple-conduction properties.
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•O3 assisted photocatalytic degradation of metolachlor was investigated.•O3 by itself is enough to achieve total removal.•High mineralization was only easily attained with O3, light ...and tested samples.•The combined method led a pronounced decrease in the toxicity of the solutions.•Prepared cataysts presented remarkable performance during metolachlor degradation.
Photocatalytic-assisted ozone degradation of metolachlor (MTLC) aqueous solutions was investigated using neat TiO2 (prepared by sol-gel method) and TiO2/carbon composite (prepared from commercial available metal oxide and carbon phase) as catalysts. In terms of MTLC degradation, O3 on its own is enough to achieve 100% removal, but the introduction of light increased the rate of removal. On the other hand, the combination of O3 with light and the tested catalysts is mandatory to reach high mineralization in short reaction times. After 60min of reaction, the TOC removal was 87% and 75% in the presence of the prepared composite and TiO2, respectively. The concentration of two short chain carboxylic acids, oxalic and oxamic acids, was followed during MTLC degradation. The amount of these acids decreased when O3 and light were combined.
In general, nitrogen ions, such as nitrate and ammonium, were detected in the studied processes. All treatments released ammonium and light based processes also produced nitrate.
Microtox® analysis showed that the combined process in the presence of the prepared catalysts led to a remarkable reduction in the toxicity of the treated solution, decreasing the inhibition of luminescent activity of Vibrio Fisheri from 74% to 12%.
Self-assembled multi-layered vertically aligned gold nanorod (AuNR) arrays have been fabricated by a simple preparation process that requires a balance between the particle concentration and the ...ionic strength of the solvent. An experimentally determined critical AuNR concentration of 2.0nM and 50mM NaCl produces well-ordered vertically aligned hexagonally close-packed AuNR arrays. We demonstrate surface treatment via UV Ozone cleaning of such samples to allow introduction of analyte molecules (benzenethiol and cannabinol) for effective surface enhanced Raman scattering detection. This is the first demonstration of the SERS analysis of cannabinol. This approach demonstrates a cost-effective, high-yield and simple fabrication route to SERS sensors with application in the screening for the cannabinoids.
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•A critical AuNR concentration is necessary for vertically aligned AuNR array.•Continued UV-Ozone irradiation of AuNR array causes catastrophic damages.•SERS detection of cannabinol with vertically aligned AuNR array•Partial removal of CTAB from AuNR promotes SERS detection of cannabinol.
•The Ni/Al2O3 catalysts was prepared by electroless plating calcination method for catalytic ozonation.•Preparation parameters and operating parameters of Ni/Al2O3-EPC catalytic ozonation system were ...optimized.•Characteristics of Ni/Al2O3-EPC and Ni/Al2O3-IC were studied comparatively.•Oxidative intermediate species in O3-Ni/Al2O3-EPC system were detected.•Mechanism of the Ni/Al2O3-EPC catalytic ozonation for succinic acid removal was proposed.
A catalyst of the Ni/Al2O3 was prepared by electroless plating-calcination (EPC) method using Al2O3 support for catalytic ozonation. To evaluate the catalytic activity of Ni/Al2O3, the O3 + Ni/Al2O3 system was set up to degrade succinic acid (SA). First, the key preparation parameters (i.e., plating time, calcination temperature and calcination time) of Ni/Al2O3 and operational parameters (i.e., initial pH, ozone flow rate and the catalyst dosage) of O3 + Ni/Al2O3 system were optimized, respectively. The maximum SA removal (100%) and total organic carbon (TOC) removal (84.7%) were obtained under the optimal conditions. Meanwhile, characteristics of the Ni/Al2O3 catalysts prepared by EPC method and traditional impregnation-calcination (IC) method were studied comparatively through scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Brunauer-Emmet-Teller (BET), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The results show that nickel oxides (NiO) was uniformly deposited on the Al2O3 surface when Ni/Al2O3 was prepared by EPC method. On the contrary, when Ni/Al2O3 was prepared by IC method, nickel oxides were heterogeneously, rough and loose distributed on the surface of Al2O3 substrate. Furthermore, Ni/Al2O3 prepared by EPC possessed higher BET surface areas, higher pore volumes and smaller pore size distribution than Ni/Al2O3 prepared by IC. Finally, the catalytic mechanism of the O3 + Ni/Al2O3 system was proposed according to the characterization of Ni/Al2O3 prepared by EPC, radical scavenging studies, hydroxyl radical (HO) and H2O2 detection experiments. Collectively, these results suggest that the EPC method was a promising technology for catalyst preparation of Ni/Al2O3 with high catalytic performance and the Ni/Al2O3 should be proposed as a promising catalyst for the decomposition of ozone.
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•Polymeric membrane was used in a membrane reactor for ozonation treatment of DEET.•The membrane reactor equipped with membrane distributor, contactor and separator.•Coating the ...membrane contactor/distributor with PAC achieved greater DEET conversion.•The additional of ferrihydrite lead to deeper DEET mineralization.•Selective removal of water resulted in efficient treatment of DEET in membrane reactor.
The ozone treatment of N,N-diethyl-meta-toluamide (DEET) in water was carried out in a membrane reactor that uses ozone-resistant polymer membranes for ozone distribution, catalytic contactor and water separation. Iron oxide (ferrihydrite) nanoparticles supported on powdered activated carbon (CAT1) were used as catalyst, and were coated on the surface of the membrane contactor/distributor. Ferrihydrites promote ozone dissolution and transformation to reactive hydroxyl radicals, and accelerate the conversion and mineralization of DEET. The powdered activated carbon helped retain the organic pollutants in the reaction zone leading to greater conversion and deeper mineralization. Consistently, the catalytic membrane contactor/distributor displayed the highest DEET conversion and TOC reduction over the entire studied range of ozone dosage and reaction residence time. The selective removal water by the membrane separator had the desired effect of concentrating the organic pollutants resulting in their improved treatment. The compact membrane reactor unit equipped with catalytic membrane contactor/distributor and membrane water separator outperformed a semi-batch ozone reactor with 60% DEET conversion compared to 20%, and 30% TOC reduction versus 5%.
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