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Although carbon surfaces are generally hydrophobic, the surface oxygen-containing groups act as water molecule sorption sites, reducing the performance of carbon molecular sieving (CMS) membranes over time. In this study, a hydrophobic poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) layer was coated on the surface of PPO- or polyetherimide (PEI)-derived CMS membranes to protect against aging. The permeation properties and anti-aging characteristics of the modified CMS membranes were explored using a single gas permeability test. Furthermore, thermal annealing below the PPO's glass transition temperature was applied to the hydrophobic layer to evaluate its anti-aging effect. The results indicate that the aging of CMS membranes was also determined by the carbon matrix structure and that a smaller pore size could prevent water adsorption and O2 chemisorption. After the hydrophobic layer was post-treated with thermal annealing, the gas diffusion resistance was diminished, and the initial permeance was retained to approximately 60%, showing slight loss within the testing period.

It is expected that the simultaneous removal of acid gases and particles from flue gas, using a single process and at the same temperature, will become an economical, and thus, desirable option. Accordingly, this study investigates the potential for the utilization of a fluidized-bed adsorbent/catalyst reactor for the simultaneous removal of SO 2 and fly ash from simulated flue gas. The operating conditions for the evaluation include: (1) different pre-treatments of the adsorbent/catalyst, (2) the operating parameters of adsorption/filtration and (3) the effects of simultaneous adsorption/filtration through the fluidized-bed reactor. Based on the experimental data gathered, the Bronsted acid sites were formed on the surface of activated carbon (AC) support materials after modification with nitric or sulfuric acid and it acted as anchor. This characteristic accounts for the promotion of the effects of dispersion and adsorption of the adsorbent/catalyst. Moreover, the addition of copper facilitated the oxygen transfer of SO 2 to the carbon matrix. The concentration of SO 2 removed by the fluidized-bed adsorbent/catalyst reactor decreased from 17.9 to 14.2 mg SO 2 /g of adsorbent after exposure to a high concentration of fly ash. Therefore, an acid-pre-treatment of the adsorbent/catalyst is required to hasten the removal of SO 2 in the simulated flue gas. Our result shows that the acidic groups may facilitate the adsorbent/catalyst removal of SO 2 when there exist high concentrations of fly ash in the flue gas.

This study investigates the potential of utilizing a fluidized-bed catalytic reactor for the simultaneous removal of NO, SO2, and coal ash from simulated flue gas. The operational conditions for th...

This study investigated the potential of a fluidized-bed sorbent/catalyst reactor for the simultaneous removals of SO2 and fly ash from a simulated flue gas containing different H2O and particles. Experimental results showed that the removal efficiency of particles and SO2 was 85%−96% and 5.75−2.97 mg SO2/g, respectively, as the H2O content was 1.5−5.3%. The activities of sorbent/catalysts for simultaneous removals of SO2 and particles were inhibited by H2O and particles, and the inhibition effects increased with the content of H2O. As the H2O content increased, the particle size distribution (PSD) of fine particles shifted to the coarse particles. The results of BET analysis show that the obstruction phenomenon of the sorbent/catalyst caused by the particles was diminished with the increased content of H2O. The results showed this aggregation phenomenon of fine particles shifted to the coarse particles may cause increased water vapor content in fluidized-bed sorbent/catalyst reactor.

Injection of bimetal (Pd/Fe) nanoparticles was evidenced as a promising treatment to remediate trichloroethene (TCE) polluted groundwater. However, the particles usually aggregate rapidly and result in a very limited migration distance. This study employed poly acrylic acid (PAA) for the synthesis of stable bimetal nanoparticles (SBN) by selecting appropriate PAA molecular weight and dosage to reduce particle aggregation. In addition, this study elucidated the SBN stabilization mechanism by analyzing morphology and characteristics. The results of TCE dechlorination and SBN stabilization experiments indicate that the bimetal nanoparticles modified with PAA250K exhibit better reactivity and stability characteristics than did other such nanoparticles. The SBN bind chemically onto PAA250K via the carboxylic group and bidentate pattern bridging, which could provide both electrostatic and steric repulsion to prevent particle aggregation. Therefore, the SBN exhibited a higher dechlorination effect than did bare bimetal. The morphology of SBN shown in the transmission electron microscopy (TEM) images exhibits capsule-like and wire-like structures instead of a single particle dispersed in the slurry. The results of this work can preliminarily elucidate the SBN's morphology, dispersion, and size distribution.

This study measured vertical distributions of ozone, sulfur dioxide, nitrogen oxide, carbon monoxide, six biogenic-related volatile organic compounds, wind vector, humidity and temperature within the Planetary Boundary Layer (PBL) below 1200 m using a tethered balloon sounding system at a downwind rural site in the Taichung Basin, Taiwan, during the 2002 summer. During ozone episodes, both nocturnal inversion and valley-mountain wind circulation were stronger than those during non-episode days. The observed vertical distributions of these pollutants indicate that the concentrations of carbon monoxide, nitrogen monoxide and biogenic volatile organic compounds decreased as the height increased. Conversely, the highest ozone concentrations were measured during early afternoon at heights of 100-600 m above ground level. Notably, these high ozone concentrations were normally accompanied by relatively higher concentrations of nitrogen dioxide and sulfur dioxide, but not carbon monoxide. From emission inventory, trajectory analysis and statistical analysis, all suggest that high-stack point sources have an important role in causing the summer ozone episodes. This suggestion is supported by 11-y summer data at three stations in the Basin. In addition, it is found that part of the early-afternoon surface ozone was from ozone stored aloft in the residue layer at heights above the nocturnal boundary layer of the preceding night.

The concentration of polycyclic aromatic hydrocarbons (PAHs) in the ambient air from a massive open burning of joss paper was simultaneously measured at an open-burning site (OS) and a downwind site (DS) from 6 to 8 August 2006. A total of 16 major PAHs (particle-bound and gas-phase) concentrations were extracted by the Soxhlet analytical method and analyzed by gas chromatography. The dominant PAHs of the total mass of the organic compound at both the sampling sites were low-molecular-weight species. Further, the results showed that the start burning/end burning-dominant PAH concentration ratios at the OS and DS were 10 and 6.2, respectively. Diagnostic ratios were also used in this study to characterize and identify the PAH emission sources. The results suggest that the characterization of air pollutants emitted from open-burning joss paper lies between furnace-burning joss paper and wood combustion.

Using a tethered balloon, vertical air pollutant concentrations (CO, SO2, NO, NO2 and O3) were measured in central Taiwan during field campaigns in the winters of 1999 and 2001. Modified novel lightweight sampling equipment was used to take samples at heights of 1, 13, 100, 300, 500 and 1200 m. A balloon was launched every 3 h and in total there were 133 flights during the three campaigns. The data were collected in order to examine the temporal and vertical variations of pollutants. The average daytime profiles showed greater vertical convection mixing in unstable circumstances. The characteristics of shapes and time behavior of profiles are reported. Except for a slight decrease near the ground and strong photochemical reactions at clear daytime, titration of O3 by NO was observed at all altitudes in the atmospheric boundary layer during these campaigns. Ground level ozone may be contributed by downward mixing from above. A fair correlation appeared between the maximum ozone concentration at the surface during the daytime ( C 0 Max ) and average ozone concentration above the NBL ( C a NBL ). A linear regression equation is shown as C 0 Max =29+0.91 C a NBL .

We developed new solutions for soil vapor extraction from a finite horizontal well in unsaturated zones by Fourier and Laplace transforms. These solutions may be applied for problems with or without laterally impervious bounds and for covered, uncovered or leaking ground surface conditions. However, the solution for the problems with laterally impervious bounds is expressed in series form. To attain good accuracy, the required number of terms for the series solution may depend on the ratio of width and depth of the problem domain. Further, with the dimensionless permeability, kD (the ratio of permeability for the leakage layer and that for the unsaturated zone) and dimensionless depth, fD (the ratio of the leakage layer depth and the unsaturated soil depth), we may find lower and upper limit values of the ratio of kD and fD for the problems representing covered and uncovered surface condition, respectively.