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A papermaking technique with a dual polyelectrolyte retention system was used for the preparation of NaY zeolite-containing papers, which implied the use of cationic and anionic polymers. Two kinds of fibers were employed, either ...
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A papermaking technique with a dual polyelectrolyte retention system was used for the preparation of NaY zeolite-containing papers, which implied the use of cationic and anionic polymers. Two kinds of fibers were employed, either cellulosic or ceramic ones, and accordingly papers with different characteristics were obtained: those that only contained cellulosic fibers for low temperature applications, cellulosic papers, and those prepared using both cellulosic and ceramic fibers - ceramic papers - for high temperature applications, Although a decrease in their mechanical properties due to calcination was observed, zeolitic ceramic papers resulted easy to handle for practical applications. Zeolite was quantified through BET surface area measurements. SEM images indicated a good dispersion of zeolite particles within the cellulosic paper whereas in the ceramic paper they appeared anchored on ceramic fibers. The zeolitic papers prepared resulted efficient as toluene sorbents, the adsorption capacities of zeolitic ceramic papers being higher than those of zeolitic cellulosic papers. In the case of zeolitic cellulosic papers, the amounts of released toluene were lower than those of adsorbed toluene, implying that the treatment up to 160 °C did not completely eliminate the hydrocarbon. Also, TPD profiles showed that toluene is chemically retained up to high temperatures (ca. 420 °C) in zeolitic ceramic papers. Toluene adsorption values demonstrate that zeolite dispersed into the cellulose/ceramic matrix is as effective as powder massive zeolite in retaining the hydrocarbon, which highlights the potential application of these zeolitic structures as sorbent materials both for low and high temperatures.
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Three kinds of hierarchical Mordenite Framework Inverted (MFI)-type nanozeolites including Si-MFI, Al-MFI and Ti-MFI were successfully synthesized by two-stage varying temperature hydrothermal treatment. Taking toluene as the prob...
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Three kinds of hierarchical Mordenite Framework Inverted (MFI)-type nanozeolites including Si-MFI, Al-MFI and Ti-MFI were successfully synthesized by two-stage varying temperature hydrothermal treatment. Taking toluene as the probe molecule, a series of methods were used to evaluate the adsorption properties of as-synthesized hierarchical zeolites samples including the adsorption breakthrough curves, simulation of adsorption isotherms as well as kinetics models and toluene-TPD (the temperature programmed desorption of toluene). The dynamic adsorption results showed that Al-MFI exhibited the highest adsorption capacity for toluene (58 mg/ g(ads) ) under dry gas condition while Ti-MFI had the optimal toluene adsorption performance (45 mg/g(ads) ) under the wet gas condition (the relative humidity was 50%). The simulation results indicated that the adsorption behavior of toluene on hierarchical MFI nanozeolites conformed to the Freundlich principle, and the pseudo-first-order adsorption model was suitable to elucidate the adsorption process. Moreover, the fitting result of intraparticle diffusion model indicated that the adsorption process was affected by multiple adsorption steps and the intraparticle diffusion was not the control step.
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A polyurethane foam medium with characteristics described in Part I of this paper was tested in a toluene degrading biofilter to demonstrate its ability to support an active biofilm and to study feasibility of a novel nutrient add...
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A polyurethane foam medium with characteristics described in Part I of this paper was tested in a toluene degrading biofilter to demonstrate its ability to support an active biofilm and to study feasibility of a novel nutrient addition and biomass wasting strategy. A laboratory-scale biofilter was fed a model waste stream containing toluene for more than 300 days using empty bed residence times ranging from 1 to 4 min and toluene concentrations ranging from 50 to 200 parts per million by volume. Results reported herein demonstrate that a polyurethane foam medium with high porosity, suitable pore size, low density, and an ability to sorb water was able to remove over 99% of the influent toluene after implementation of a nutrient addition and biomass removal strategy. The strategy, made possible by use of the foam medium, overcame problems such as clogging, high head loss, moisture content control, and nutrient limitation that are often associated with conventional biofilter operation. [References: 36]
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A hybrid titanium dioxide (TiO2)-integrated photoionization enhanced atmospheric pressure plasma corona system was developed for effective toluene removal. The individual and synergistic effects of a corona discharge, a photoioniz...
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A hybrid titanium dioxide (TiO2)-integrated photoionization enhanced atmospheric pressure plasma corona system was developed for effective toluene removal. The individual and synergistic effects of a corona discharge, a photoionizer irradiation with a soft x-ray source, and a TiO2 photocatalyst on toluene removal were investigated by performing various experiments. Voltage-current characteristics revealed a lower corona inception voltage and a higher current at the same voltage caused by combining the corona discharge, the photoionizer irradiation, and the TiO2 photocatalyst. The toluene removal efficiency was significantly enhanced by combining the corona discharge, the photoionizer irradiation, and the TiO2 photocatalyst: (corona discharge + photoionizer irradiation + TiO2: similar to 86.0%) > (corona discharge + TiO2: similar to 70.8%) > (corona discharge + photoionizer irradiation: similar to 51.1%) > (corona discharge: similar to 43.8%). The toluene removal efficiency increased with an increase in the photoionizer energy. These trends were mainly due to the degree of ion generation in the system. Corona discharge generates ions inside the system, and ion concentration increases as the applied voltage is increased. The photoionizer creates positive and negative ions, which lowers the corona inception voltage and enhances the current. The TiO2 film also enhances ion production under corona discharge, and is activated by photoionizer irradiation to create additional electron-hole pairs. In addition, the rougher surface induced by the morphology change in TiO2 under corona discharge has a positive effect on toluene removal.
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摘要 :
A hybrid titanium dioxide (TiO2)-integrated photoionization enhanced atmospheric pressure plasma corona system was developed for effective toluene removal. The individual and synergistic effects of a corona discharge, a photoioniz...
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A hybrid titanium dioxide (TiO2)-integrated photoionization enhanced atmospheric pressure plasma corona system was developed for effective toluene removal. The individual and synergistic effects of a corona discharge, a photoionizer irradiation with a soft x-ray source, and a TiO2 photocatalyst on toluene removal were investigated by performing various experiments. Voltage-current characteristics revealed a lower corona inception voltage and a higher current at the same voltage caused by combining the corona discharge, the photoionizer irradiation, and the TiO2 photocatalyst. The toluene removal efficiency was significantly enhanced by combining the corona discharge, the photoionizer irradiation, and the TiO2 photocatalyst: (corona discharge + photoionizer irradiation + TiO2: similar to 86.0%) > (corona discharge + TiO2: similar to 70.8%) > (corona discharge + photoionizer irradiation: similar to 51.1%) > (corona discharge: similar to 43.8%). The toluene removal efficiency increased with an increase in the photoionizer energy. These trends were mainly due to the degree of ion generation in the system. Corona discharge generates ions inside the system, and ion concentration increases as the applied voltage is increased. The photoionizer creates positive and negative ions, which lowers the corona inception voltage and enhances the current. The TiO2 film also enhances ion production under corona discharge, and is activated by photoionizer irradiation to create additional electron-hole pairs. In addition, the rougher surface induced by the morphology change in TiO2 under corona discharge has a positive effect on toluene removal.
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Gaseous toluene, one of the volatile organic compounds, has aroused wide concerns in China due to its growing emissions and harmfulness. Herein, novel manganese decorated UIO-66 catalysts (Mn/UIO-66) were prepared by hydrothermal ...
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Gaseous toluene, one of the volatile organic compounds, has aroused wide concerns in China due to its growing emissions and harmfulness. Herein, novel manganese decorated UIO-66 catalysts (Mn/UIO-66) were prepared by hydrothermal synthesis and applied to the vaporized hydrogen peroxide system for toluene removal. TEM, BET, XRD, ICP, and XPS were used to analyze the chemical and physical characteristics of Mn/UIO-66. A toluene removal efficiency of 82% with the 3-Mn/UIO-66 catalyst in the vaporized hydrogen peroxide system could achieved. The effects of different reaction conditions (reaction temperature, hydrogen peroxide concentration, and initial toluene concentration) on toluene removal were determined. The yield of hydroxyl radical in the Mn/ UIO-66 catalyst combined with the hydrogen peroxide system was positively correlated with the Mn decorated ratio. Results suggested that the catalytic performance is related not only to the yield of hydroxyl radical but also to the catalyst specific surface. The intermediate products during toluene removal were analyzed by gas chromatography-mass spectrometry (GC-MS), and the possible reaction pathway of toluene removal was proposed.
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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 (G...
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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 mu M 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.
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Hybrid materials based on halloysite nanotubes (HNT) and cucurbit[ 8]uril (CB[8]) were prepared with the aim to obtain efficient nanosponges towards hydrocarbons both in liquid and vapor phases. The loading on both HNT surfaces an...
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Hybrid materials based on halloysite nanotubes (HNT) and cucurbit[ 8]uril (CB[8]) were prepared with the aim to obtain efficient nanosponges towards hydrocarbons both in liquid and vapor phases. The loading on both HNT surfaces and the hybrid morphology were evidenced by FTIR spectroscopy, thermogravimetric analysis and scanning electron microscopy. In order to highlight the interactions in the hybrid ~(13)C {~1H} CP-MASNMR experiments were performed. The aqueous colloidal stability of HNT/CB[8] was highlighted through ζ potential and dynamic light scattering measurements. The HNT/CB[8] composite was employed as nanosponge to capture aromatic oils in aqueous phase as evidenced by fluorescence emission spectra of pyrene. These results were correlated with the adsorption capacity of the hybrid toward toluene in vapor phase. This paper provides an efficient way to prepare a biocompatible hybrid material that could be used as a potential multi-pockets nano-container for decontamination of polluted water and/or air.
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Due to the large diameter and small surface, the contaminant degradation by conventional calcium peroxide (CaO_2) is slow with high dosage required. The aggregation of conventional CaO_2 also makes it difficult to operate. Nanosca...
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Due to the large diameter and small surface, the contaminant degradation by conventional calcium peroxide (CaO_2) is slow with high dosage required. The aggregation of conventional CaO_2 also makes it difficult to operate. Nanoscale CaO_2 was therefore synthesized and applied to remove toluene in this study. Prepared from nanoscale Ca(OH)_2 and H_2O_2 in the ratio of 1:7, the finely dispersed nanoscale CaO_2 particles were confirmed by the scanning electron microscope to be in the range of 100-200 nm in size. Compared to their non nanoscale counterparts, the synthesized nanoscale CaO_2 demonstrated a superior performance in the degradation of toluene, which could be eliminated in 3 d at pH 6. The oxidation products of toluene were analyzed to include benzyl alcohol, benzaldehyde and three cresol isomers. With the addition of 2-propanol, hydroxyl radicals were indicated as the main reactive oxygen species in the oxidation of toluene by nanoscale CaO_2. Superoxide radicals were also investigated as the marker of nanoscale CaO_2 in the solution. Our study thus provides an important insight into the application of nanoscale CaO_2 in the removal of toluene contaminants, which is significant, especially for controlling the petroleum contaminations.
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A surfactant-free emulsion polymerization process was developed to produce hollow hybrid nanoparticles (HHNP thereafter). Ultrasonication was found not only to help the generation of nanosized monomer droplets but also to generate...
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A surfactant-free emulsion polymerization process was developed to produce hollow hybrid nanoparticles (HHNP thereafter). Ultrasonication was found not only to help the generation of nanosized monomer droplets but also to generate surface active species through mediating the hydrolysis of the monomer, 3-(methacryloyloxy) propyltrimethoxysilane (MPS), thus stabilizing the oil/water interface. The hollow structure was formed based on a soft template approach, where the partially hydrolyzed monomer served as emulsifier and polymerized at the interface to form a hybrid shell. These HHNPs were used to absorb dissolved toluene in water and it was found they could reduce the toluene level down to zero, a level hardly being achieved by other methods. Combined with their good colloidal stability in water, these HHNPs are very promising colloidal collectors for dissolved organic solvents, in order to generate high quality water from contaminated water.
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