Vertical stratification of volatile organic compounds and their photochemical product formation potential in an industrial urban area.

High emissions of volatile organic compounds (VOCs) from the petrochemical industry and vehicle exhaust may contribute to high ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP). In this study, the vertical profiles of VOCs were created for the southern Taiwan industrial city of Kaohsiung. Vertical air samples were collected up to 1000 m using an unmanned aerial vehicle (UAV). In Renwu District, VOC distribution was affected by the inversion layer up to 200 m height. Total VOCs (36-327 ppbv), OFP (66-831 ppbv) and SOAFP (0.12-5.55 ppbv) stratified by height were the highest values at 300 m. The VOCs originated from both local and long-distance transport sources. These findings can be integrated into Kaohsiung's future air quality improvement plans and serve as a reference for other industrialized areas worldwide.

Investigating the differences between receptor and dispersion modeling for concentration prediction and health risk assessment of volatile organic compounds from petrochemical industrial complexes.

Receptor and dispersion models both provide important information to help understand the emissions of volatile organic compounds (VOCs) and develop effective management strategies. In this study, differences between the predicted concentrations of two models and the associated impacts on the estimated health risks due to different theories behind two models were investigated. Two petrochemical industrial complexes in Kaohsiung city of southern Taiwan were selected as the sites for this comparison. Although the study compares the approaches by applying the methods to this specific area, the results are expected to be adopted for other areas or industries. Ninety-nine VOC concentrations at eight monitoring sites were analyzed, with the effects of diurnal temperature and seasonal humidity variations being considered. The Chemical Mass Balance (CMB) receptor model was used for source apportionment, while the Industrial Source Complex (ISC) dispersion model was used to predict the VOC concentrations at receptor sites. In the results of receptor modeling, 54% ± 11% and 49% ± 20% of the monitored concentrations were contributed by process emissions in two complexes, whereas the numbers increased to 78% ± 41% and 64% ± 44% in the results of dispersion modeling. Significant differences were observed between two model predictions (p < 0.05). The receptor model was more reproducible given the smaller variances of its results. The effect of seasonal humidity variation on two model predictions was not negligible. Similar findings were observed given that the cancer and non-cancer risks estimated by the receptor model were lower but more reproducible. The adverse health risks estimated by the dispersion model exceeded and were 75.3%-132.4% of the values estimated by using the monitored data, whereas the percentages were lowered to the range from 27.4% to 53.8% when the prediction was performed by using the receptor model. As the results of different models could be significantly different and affect the final health risk assessment, it is important to carefully choose an appropriate model for prediction and to evaluate by monitoring to avoid providing false information for appropriate management.

Volatile organic compounds in ambient air of a major Asian port: spatiotemporal variation and source apportionment.

This study investigated the spatiotemporal variation and source characteristics of volatile organic compounds (VOCs) in Kaohsiung Harbor, one of the busiest ports in the world. The VOCs' potential to form ozone (O3) and secondary organic aerosols (SOAs) was also examined. The temporal variation was studied in February, May, July, and November of 2020, while the spatial distribution was investigated in the export processing zone (KEPZ) and at the two port entrances (E1 and E2). The most polluted month in the harbor was November (37.7 ± 12.6 ppbv), while the most polluted site was the industrial area (KEPZ). A significant positive correlation was found between VOCs and O3 (r = 0.985). Meanwhile, a moderate positive correlation (r = 0.449) was observed between VOCs and secondary organic aerosol formation potential (SOAFP), mainly affected by the concentration of toluene in the study area. The diagnostic ratios indicated that the air parcels in the site were "fresh," and three possible ambient sources of VOC were identified by the positive matrix factorization (PMF): industrial emissions (53.6%), freight transport emissions (29.6%), and others (17.7%). The study highlights the current state of VOCs and their potential sources in the port city of Kaohsiung, which can be used to enhance the strategies for regulating and controlling industrial activities and improving air pollution control measures to reduce VOC emissions.

Influence of sea-land breezes on the tempospatial distribution of atmospheric aerosols over coastal region.

The influence of sea-land breezes (SLBs) on the spatial distribution and temporal variation of particulate matter (PM) in the atmosphere was investigated over coastal Taiwan. PM was simultaneously sampled at inland and offshore locations during three intensive sampling periods. The intensive PM sampling protocol was continuously conducted over a 48-hr period. During this time, PM2.5 and PM(2.5-10) (PM with aerodynamic diameters < 2.5 microm and between 2.5 and 10 microm, respectively) were simultaneously measured with dichotomous samplers at four sites (two inland and two offshore sites) and PM10 (PM with aerodynamic diameters < or =10 microm) was measured with beta-ray monitors at these same 4 sites and at 10 sites of the Taiwan Air Quality Monitoring Network. PM sampling on a mobile air quality monitoring boat was further conducted along the coastline to collect offshore PM using a beta-ray monitor and a dichotomous sampler. Data obtained from the inland sites (n=12) and offshore sites (n=2) were applied to plot the PM10 concentration contour using Surfer software. This study also used a three-dimensional meteorological model (Pennsylvania State University/National Center for Atmospheric Research Meteorological Model 5) and the Comprehensive Air Quality Model with Extensions to simulate surface wind fields and spatial distribution of PM10 over the coastal region during the intensive sampling periods. Spatial distribution of PM10 concentration was further used in investigating the influence of SLBs on the transport of PM10 over the coastal region. Field measurement and model simulation results showed that PM10 was transported back and forth across the coastline. In particular, a high PM10 concentration was observed at the inland sites during the day because of sea breezes, whereas a high PM10 concentration was detected offshore at night because of land breezes. This study revealed that the accumulation of PM in the near-ocean region because of SLBs influenced the tempospatial distribution of PM10 over the coastal region.

Partition and tempospatial variation of gaseous and particulate mercury at a unique mercury-contaminated remediation site.

This study investigated the seasonal variation and spatial distribution of gaseous and particulate mercury at a unique mercury-contaminated remediation site located at the near-coastal region of Tainan City, Taiwan. Gaseous elemental mercury (GEM), particulate mercury (PTM), and dustfall mercury (DFM) were measured at six nearby sites from November 2009 to September 2010. A newly issued Method for Sampling and Analyzing Mercury in Air (National Institute of Environmental Analysis [NIEA] Method A304.10C) translated from U.S. Environmental Protection Agency (EPA) Method 10-5, was applied for the measurement of atmospheric mercury in this particular study. One-year field measurements showed that the seasonal averaged concentrations of GEM and PTM were in the range of 5.56-12.60 and 0.06-0.22 ng/m3, respectively, whereas the seasonal averaged deposition fluxes of DFM were in the range of 27.0-56.8 g/km2-month. The maximum concentrations of GEM and PTM were 38.95 and 0.58 ng/m3, respectively. The atmospheric mercury apportioned as 97.42-99.87% GEM and 0.13-2.58% PTM. As a whole, the concentrations of mercury species were higher in the springtime and summertime than those in the wintertime and fall. The southern winds generally brought higher mercury concentrations, whereas the northern winds brought relatively lower mercury concentrations, to the nearby fishing villages. This study revealed that the mercury-contaminated remediation site, an abandoned chlor-alkali manufacturing plant, was the major mercury emission source that caused severe atmospheric mercury contamination over the investigation region. The hot spot of mercury emissions was allocated at the southern tip of the abandoned chlor-alkali manufacturing plant. On-site continuous monitoring of GEM at the mercury-contaminated remediation site observed that GEM concentrations during the open excavation period were 2-3 times higher than those during the nonexcavation period.

Photoelectrochemical properties of N/C-codoped TiO2 film electrodes prepared by reactive DC magnetron sputtering.

This paper aims to characterize the photoelectrochemical properties of the visible-light enabling titanium dioxide (TiO2) film electrodes prepared by codoping nitrogen (N) and a presputtered carbon film (C-film) onto indium tin oxide (ITO) glass substrates using a direct current (DC) magnetron sputtering technique. To improve its photoelectrochemical properties, different amount of C-doping sources, 2 h and 4 h C-film, are chose to prepare the N/C-codoped TiO2 film electrodes. Under visible-light (420 < lambda < 610 nm) illumination, a remarkable photocurrent density of 22 microA/cm2 is obtained for the N/C-TiO2 film electrode prepared with a 4 h C-film (NC(4)-T) at an applied potential of +1.2 V versus SCE. Under ultraviolet (lambda approximately 365 nm) illumination, the NC(4)-T film electrode also exhibits the highest photocurrent density of 0.23 mA/cm2 among all samples tested. A more negative flat band potential of NC(4)-T film electrode is attributed to the synergistic effect of N/C codoping. The XRD spectrum of the NC(4)-T film electrode shows mainly the well-crystallized anatase TiO2 phase and an extremely intense (211) plane. Thus, photoelectrochemical activity of the NC(4)-T film electrode can be ascribed to the well-crystallized columnar crystals with pores at its grain boundary, open surface morphology, which are revealed by SEM and TEM images, and a more negative flat band potential. The visible-light induced activity is mostly enhanced as a result of the synergistic effects of N/C-codoping into the TiO2 crystals. A potential application to photocatalytic splitting of water for hydrogen evolution using solar light is practically possible.

Chemical fingerprint and source apportionment of PM2.5 in highly polluted events of southern Taiwan.

To investigate the spatial distribution and diurnal variation of the chemical composition of PM2.5 pollution in an industrial city of southern Taiwan, 12-h PM2.5 was diurnally continuously collected simultaneously at the Kaoping Air Quality Zone (KAQZ) during one highly PM2.5-polluted episode. Water-soluble ions, metallic elements, carbonaceous contents, dicarboxylic acids, and anhydrosugars were analyzed to characterize the chemical fingerprint of PM2.5. Backward trajectory simulation and chemical mass balance (CMB) receptor modeling were applied to identify the potential sources of PM2.5 and their contributions. It showed that Chaozhou (rural area) accompanying the highest SORs and NORs suffered from the most severe PM2.5 pollution during the episode. Sulfate (SO42-) was probably formed by the atmospheric chemical reaction in the daytime, while NO3- processed at nighttime at the KAQZ. A homogeneous formation of NO3- occurred at Chaozhou. The concentrations of Zn, Pb, Fe, Cu, V, and Al, mainly emitted from anthropogenic sources, increased significantly at the KAQZ. The highest OC, SOC/OC, and DA/OCs at Daliao (industrial area) were attributed to the transformation of primary VOCs to secondary OC via photo-oxidation during the episode. Oxalic acid was mainly produced through photochemical reactions since a high correlation between oxalic acid and Ca2+ was observed at Nanzi (urban area) and Daliao during the episode. During the episode, PM2.5 mostly originated from local primary or secondary aerosol than long-range overseas transport. The dominant source was anthropogenic emissions, accounting for 67.1% and 70.4% of PM2.5 at Nanzi and Daliao, respectively. At Chaozhou, the contribution of anthropogenic emissions was the lowest (42.4%), but secondary aerosols had the highest contribution of 38.3% of PM2.5 among the three areas during the episode.

Visible-light-responsive layered titanium oxide/tin indium oxide catalysts for hydrogen production.

Visible-light-responsive layered titanium dioxide/tin indium oxide (TiO2/ITO) catalysts prepared on unheated glass slides by DC magnetron sputtering were investigated in this study. Transmittance spectra of the catalyst revealed that an interference pattern gradually appeared at wavelengths of 550-650 nm which indicated a strong light absorption up to this region. The red-shift may be ascribed to the difference in both compositions and phase structures of the layered catalyst. X-ray diffraction (XRD) and scanning electron microscopy (SEM) exhibited a strong columnar growth morphology with highly faceted grains and a distinct (211) texture. Selected area electron diffraction (SAED) measurements also confirmed the crystalline nature of the layered catalyst. The SIMS elemental depth profiles showed that tin atoms permeated into the overlaid TiO2 film. This could be resulted from the diffusion of tin from the intercalated ITO thin film during the TiO2 deposition. It suggested that the tin atoms played an important role on the microstructure formation and on the catalytic property of the layered catalyst. This was also confirmed by the cross-sectional TEM images where a layer of crystalline anatase TiO2 grown epitaxially above the intercalated ITO thin film was observed. In addition, a better crystalline TiO2 film with larger grains of 120-180 nm and a higher specific surface area of 1.55 was obtained on successively coated ITO substrate. The layered catalysts showed significant photocatalytic activity on methylene blue (MB) degradation illuminated by ultra-violet (UV 365 nm) and visible light (420 < lambda < 620 nm) sources. A preliminary study on water splitting for hydrogen production showed that a noticeable amount of hydrogen was generated at Pt cathode by employing electrical potential (approximately 0.5 V) and UV-light and visible (lambda > 420 nm) sources via a TiO2/ITO anode.

Polychlorinated dibenzo-p-dioxin and dibenzofuran emissions from an industrial park clustered with metallurgical industries.

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from an industrial park operated as Taiwan's center of metallurgical industries were investigated. The characteristics of mean PCDD/F I-TEQ concentrations, congener profiles and emission factors of each source were studied over samples of stack flue gases of individual sources. Different characteristics of congener profiles and large variations of emission factors of secondary aluminum smelters (ALSs) were observed. The mean emission factors of electric arc furnaces were comparable to those for ALSs and much greater than those of municipal solid waste incinerators and sinter plants, but still less than that of clinical waste incinerators. Annual PCDD/F emission contribution of each source was estimated, raising critical concerns over the overall PCDD/F emissions from metallurgical processes. The metallurgical industries altogether contributed approximately 98.1% of the total annual emissions, while waste incinerators only 1.9%. The contributions by sinter plants and metallurgical industries to the total annual emissions of the Park were much higher than the corresponding national averages of Taiwan. The combined dioxin emissions from the entire metallurgical processes and their controls should be seriously envisaged by industrial parks devoted to metal productions.

Using in situ modification to enhance organic fouling resistance and rejection of pharmaceutical and personal care products in a thin-film composite nanofiltration membrane.

A commercially available nanofiltration membrane, NF90, was modified using an in situ concentration polarization-enhanced radical graft polymerization method to improve the organic fouling resistance as well as the removal of pharmaceutical and personal care products (PPCPs), including ibuprofen (IBU), carbamazepine, sulfadiazine, sulfamethoxazole, sulfamethazine, and triclosan (TRI). 3-Sulfopropyl methacrylate potassium salt (SPM) and 2-hydroxyethyl methacrylate (HEMA) were used in various dosages for surface modification, and the extent of membrane modifications was quantified based on the degree of grafting. The modified NF90 exhibited a 15-40% lower flux during humic acid (HA) fouling and 25% greater NaCl rejection compared with the virgin membrane. PPCP rejection in the modified NF90 membranes before and after HA fouling was 20-45% and 5-20% greater, respectively, compared with that of the virgin membrane. Both SPM and HEMA increased the hydrophilicity of NF90 by decreasing contact angles. Scanning electron microscopy revealed lower amounts of foulants on the modified NF90 than on the virgin membrane. The main fouling mechanism for virgin NF90 was gel layer formation and those for modified NF90 were complete and intermediate blocking. Therefore, the modification of NF90 was effective for controlling organic fouling and strongly rejecting PPCPs.

Chemisorption and kinetic mechanisms of elemental mercury on immobilized V2O5/TiO2 at low temperatures.

To investigate the effect of low temperature and catalyst filling pattern on the adsorption of Hg° by DeNOx equipment, the chemisorption and kinetic mechanisms of Hg° adsorption on 5-30%V2O5/TiO2 immobilized on glass beads at 100-160 °C were investigated. The effects of the reaction temperature, influent Hg° concentration, and V2O5 doping amount on the adsorption efficiency and capacity for Hg° were explored. The active sites for Hg° adsorption were further identified. Additionally, the adsorption kinetics were modelled using the linear driving force approximation, Fick's diffusion model, and pseudo-second-order kinetic model. Finally, the influence of immobilization on the adsorption of Hg° was also investigated. Experimental results showed that the bridged oxygen atom of V-O-V played a key role in the adsorption of Hg°. The Hg° adsorption efficiencies decreased from >90% to 40% as the reaction temperature increased from 120 °C to 160 °C for 20%V2O5/TiO2, while the adsorptive capacities for Hg° were highly influenced by the influent Hg° concentration and V2O5 doping amount. 20%V2O5/TiO2 had the highest adsorptive capacity of 2547 µg Hg°/g V2O5/TiO2 at 160 °C. The kinetic results showed that the linear driving force approximation model fit the Hg° adsorption better than the other models. The diffusion resistance increased significantly for the immobilized catalysts because the external mass transfer coefficient decreased by more than 1200-fold.

Surface functional characteristics (C, O, S) of waste tire-derived carbon black before and after steam activation.

The effects of steam activation on the surface functional characteristics of waste tire-derived carbon black were investigated. Two carbon-based materials, powdered carbon black (PCB) and PCB-derived powdered activated carbon (PCB-PAC), were selected for this study. A stainless steel tubular oven was used to activate the PCB at an activation temperature of 900 degrees C and 1 atm using steam as an activating reagent. X-ray photoelectron spectroscopy (XPS) was adopted to measure the surface composition and chemical structure of carbon surface. Various elemental spectra (C, O, and S) of each carbon sample were further deconvoluted by peak synthesis. Results showed that the surfaces of PCB and PCB-PAC consisted mainly of C-C and C-O. The PCB-PAC surface had a higher percentage of oxygenated functional groups (C=O and O-C=O) than PCB. The O1s spectra show that the oxygen detected on the PCB surface was mainly bonded to carbon (C-O), whereas the oxygen on the PCB-PAC surface could be bonded to hydrogen (O-H) and carbon (C-O). Sulfur on the surface of PCB consisted of 58.9 wt% zinc sulfide (ZnS) and 41.1 wt% S=C=S, whereas that on the surfaces of PCB-PAC consisted mainly of S=C=S. Furthermore, the increase of oxygen content from 9.6% (PCB) to 11.9% (PCB-PAC) resulted in the increase of the pH values of PCB-PAC after steam activation.

Application of RuO2/Ni foam electrodes for remediation of ibuprofen in soil matrix-the effect of electrokinetic parameters.

Pharmaceuticals and personal care products (PPCPs) are an extraordinary and diverse group of chemicals used in veterinary medicine, agriculture, and for human health and cosmetics care. They are considered emerging contaminants and have raised great concern in recent years. Among the PPCPs, ibuprofen (IBP) is one of the most known non-steroidal anti-inflammatory drugs, which has been found at a high concentration in irrigation water in the USA and showed harmful effect for organisms. This study examined IBP degradation performance by an electrokinetic process coupled with 24-96 cm2 of RuO2/Ni foam (RN) electrodes applied 1-3 V cm-1 potential gradient for 5-9 days. The electroosmosis permeabilities (k e) and the treatment efficiency of IBP increased from 1.5 × 10-4 to 1.8 × 10-4 cm2 V-1 s-1 and from 65.4 to 78.4%, respectively, as the potential gradient increased from 1 to 3 V cm-1. The k e values also increased with electrode area, but it was much less insignificant than that of the potential gradient. Prolonging the treatment time and increasing the electrode area only enhanced the IBP remediation efficiency by a trivial amount. The degradation mechanism was more critical for IBP remediation than was the electrokinetic (EK) removal mechanism. A cost analysis revealed that processing fluid accounted for 84.1-87.6% of the operation cost. The electrode characteristics and the treatment mechanism are also discussed. This study confirmed that the IBP-contaminated soil was successfully remediated by electrokinetic process coupled with RN electrodes.

Electrochemical degradation of ibuprofen-contaminated soils over Fe/Al oxidation electrodes.

Ibuprofen (IBP) is one of the most known non-steroidal anti-inflammatory drugs. Due to the high consumption and the several ways of discharge, both the aquifer and soil matrix were contaminated by IBP. This study examined the degradation of the IBP in a soil matrix over Fe/Al oxidation electrodes in an electrokinetic system with processing fluids of sodium dodecylsulfate (SDS). The preparation of the Fe/Al oxidation electrode was carried out at a calcination temperature of 500, 550, and 600 °C, which accounted for Fe3+ coating rate of 3.89 ±â€¯0.03%, 4.62 ±â€¯0.04%, and 4.72 ±â€¯0.04%, respectively. Results indicated the generation of hydroxyl radical was proportional to the coating rate of Fe3+ on the electrode. A 200 mg kg-1 of IBP-spiked soil sample was conducted in an electrokinetic system under a potential gradient of 2 V cm-1. The experimental parameters included electrode area of 11-33 cm2 and treatment time of 5-9 days. The remediation efficiency of IBP in the EK systems coupled with Fe/Al oxidation electrode was 70.1-94.6%, which was highly dependent on H2O2 addition, electrode area, and treatment time. Both addition of H2O2 and prolonging treatment time significantly enhanced the degradation of IBP. Whereas increasing electrode area was only favorable for removal mechanism of IBP. Five reaction mechanisms were clearly provided in this study. The aluminum plays an electron donner to trigger Fenton-like reaction continuously to produce hydroxyl radicals. This study confirmed that the electrokinetic process coupled with Fe/Al oxidation electrodes is a viable technique for the remediation of IBP-contaminated soil. Make good use of redox characteristic of aluminum to trigger the Fenton-like reaction in Fe2+-rich environment is a great success in this study. The use of Fe/Al electrodes effectively expands the application of electrochemical degradation in soil remediation.

Removing volatile organic compounds in cooking fume by nano-sized TiO2 photocatalytic reaction combined with ozone oxidation technique.

Chinese cooking fume is one of the sources of volatile organic compounds (VOCs) in the air. An innovative control technology combining photocatalytic degradation and ozone oxidation (UV/TiO2+O3) was developed to decompose VOCs in the cooking fume. Fiberglass filter (FGF) coated with TiO2 was prepared by an impregnation procedure. A continuous-flow reaction system was self-designed by combining photocatalysis with advanced ozone oxidation technique. By passing the simulated cooking fume through the FGF, the VOC decomposition efficiency in the cooking fume could be increased by about 10%. The decomposition efficiency of VOCs in the cooking fume increased and then decreased with the inlet VOC concentration. A maximum VOC decomposition efficiency of 64% was obtained at 100 ppm. Similar trend was observed for reaction temperature with the VOC decomposition efficiencies ranging from 64 to 68%. Moreover, inlet ozone concentration had a positive effect on the decomposition of VOCs in the cooking fume for inlet ozone≤1000 ppm and leveled off for inlet ozone>1000 ppm. 34% of VOC decomposition efficiency was achieved solely by ozone oxidation with or without near-UV irradiation. A maximum of 75% and 94% VOC decomposition efficiency could be achieved by O3+UV/TiO2 and UV/TiO2+O3 techniques, respectively. The maximum decomposition efficiencies of VOCs decreased to 79% for using UV/TiO2+O3 technique with adding water in the oil fume. Comparing the chromatographical species of VOCs in the oil fume before and after the decomposition of VOCs by using UV/TiO2+O3technique, we found that both TVOC and VOC species in the oil fume were effectively decomposed.

Photodegradation of diethyl phthalate with PANi/CNT/TiO2 immobilized on glass plate irradiated with visible light and simulated sunlight-effect of synthesized method and pH.

Diethyl phthalate (DEP) is one of the most common phthalates for industrial use and has widely spread in environment. A series of PANi/CNT/TiO2 potocatalysts immobilized on glass plate irradiated with visible light were presented to degrade DEP in this study. The PANi/CNT/TiO2 potocatalysts were fabricated by co-doping with polyaniline (PANi) and two functionalized CNT (CNT-COCl and CNT-COOH) onto TiO2 followed by a hydrothermal synthesis and a sol-gel hydrolysis. Doping of PANi resulted in the absorption edge of the fabricated potocatalysts shifting to 421-437nm and the most distinguished red-shift effect was found in hydrothermal synthesized photocatalysts. The best DEP degradation of 41.5-59.0% and 44.5-67.4% was found in the simulated sunlight system irradiated for 120min for sol-gel hydrolysis PANi/CNT/TiO2 photocatalysts and hydrothermal synthesized ones, respectively. The optimum pH was determined at 5.0 and 7.0 for the two PANi/CNT/TiO2 photocatalysts mentioned above, respectively. The reusability of the sol-gel hydrolyzed photocatalysts up to 5 times was observed no decline in the photodegradation efficiency but less photocatalytic stability of the hydrothermal synthesized ones was found. Meanwhile, the active species of OH radicals generated in the DEP degradation system was identified by free radical scavenging experiments.

Preparation and Application of Immobilized Surfactant-Modified PANi-CNT/TiO2 under Visible-Light Irradiation.

Hydrothermally and sol-gel-synthesized immobilized surfactant-modified polyaniline-carbon nanotubes/TiO2 (PANi-CNT/TiO2) photocatalysts were prepared and their application in the degradation of diethyl phthalate (DEP) under visible light at 410 nm was investigated in this sturdy. To improve the dispersion of nanoparticles and the transfer of electrons, the TiO2 surface was modified with both sodium dodecyl sulfate (SDS) and functionalized carbon nanotubes (CNT-COOH and CNT-COCl). With the addition of PANi, which was increased from 1%-5%, the adsorption edge of the prepared photocatalysts shifted to 442 nm. The SDS linked the PANi polymers to achieve a thickness of coating of the film of up to 314-400 nm and 1301-1600 nm for sol-gel hydrolysis and hydrothermally-synthesized photocatalysts, respectively. An appropriate film thickness would extend the transfer path of the electrons and inhibit the recombination of the electrons and the electron-holes. The photo-degradation performance of DEP by the hydrothermally-synthesized photocatalysts was better than those by sol-gel hydrolysis. The results revealed that the hydroxyl radicals were the key oxidant in the degradation of DEP using hydrothermally-synthesized PANi-CNT/TiO2 photocatalysts. The morphology and functional groups of the raw materials of photocatalysts were characterized and a comparison of photocatalytic activity with other TiO2-based photocatalysts was also provided.

The adsorptive capacity of vapor-phase mercury chloride onto powdered activated carbon derived from waste tires.

Injection of powdered activated carbon (PAC) upstream of particulate removal devices (such as electrostatic precipitator and baghouses) has been used effectively to remove hazardous air pollutants, particularly mercury-containing pollutants, emitted from combustors and incinerators. Compared with commercial PACs (CPACs), an alternative PAC derived from waste tires (WPAC) was prepared for this study. The equilibrium adsorptive capacity of mercury chloride (HgCl2) vapor onto the WPAC was further evaluated with a self-designed bench-scale adsorption column system. The adsorption temperatures investigated in the adsorption column were controlled at 25 and 150 degrees C. The superficial velocity and residence time of the flow were 0.01 m/sec and 4 sec, respectively. The adsorption column tests were run under nitrogen gas flow. Experimental results showed that WPAC with higher Brunauer-Emmett-Teller (BET) surface area could adsorb more HgCl2 at room temperature. The equilibrium adsorptive capacity of HgCl2 for WPAC measured in this study was 1.49 x 10(-1) mg HgCl2/g PAC at 25 degrees C with an initial HgCI2 concentration of 25 microg/m3. With the increase of adsorption temperature < or = 150 degrees C, the equilibrium adsorptive capacity of HgCl2 for WPAC was decreased to 1.34 x 10(-1) mg HgCl2/g PAC. Furthermore, WPAC with higher sulfur contents could adsorb even more HgCl2 because of the reactions between sulfur and Hg2+ at 150 degrees C. It was demonstrated that the mechanisms for adsorbing HgCl2 onto WPAC were physical adsorption and chemisorption at 25 and 150 degrees C, respectively. Experimental results also indicated that the apparent overall driving force model appeared to have the good correlation with correlation coefficients (r) > 0.998 for HgCl2 adsorption at 25 and 150 degrees C. Moreover, the equilibrium adsorptive capacity of HgCl2 for virgin WPAC was similar to that for CPAC at 25 degrees C, whereas it was slightly higher for sulfurized WPAC than for CPAC at 150 degrees C.

Determination of the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon using thermogravimetric analysis.

This study investigated the use of thermogravimetric analysis (TGA) to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon (PAC). The technique is commonly applied to remove mercury-containing air pollutants from gas streams emitted from municipal solid waste incinerators. An alternative form of powdered activated carbon derived from a pyrolyzed tire char was prepared for use herein. The capacity of waste tire-derived PAC to adsorb vapor-phase HgCl2 was successfully measured using a self-designed TGA adsorption system. Experimental results showed that the maximum adsorptive capacities of HgCl2 were 1.75, 0.688, and 0.230 mg of HgCl2 per gram of powdered activated carbon derived from carbon black at 30, 70, and 150 degrees C for 500 microg/m3 of HgCl2, respectively. Four adsorption isotherms obtained using the Langmuir, Freundlich, Redlich-Peterson, and Brunauer-Emmett-Teller (BET) models were used to simulate the adsorption of HgCl2. The comparison of experimental data associated with the four adsorption isotherms indicated that BET fit the experimental results better than did the other isotherms at 30 degrees C, whereas the Freundlich isotherm fit the experimental results better at 70 and 150 degrees C. Furthermore, the calculations of the parameters associated with Langmuir and Freundlich isotherms revealed that the adsorption of HgCl2 by PAC-derived carbon black favored adsorption at various HgCl2, concentrations and temperatures.

Photodegradation of ibuprofen by TiO2 co-doping with urea and functionalized CNT irradiated with visible light - Effect of doping content and pH.

Ibuprofen (IBP) is one kind of non-steroidal anti-inflammatory drugs (NSAIDs), which are classified as Pharmaceuticals and Personal Care Products (PPCPs). IBP possesses bioactive property and the substantial use of IBP results in a harmful impact on bioreceptors even in small concentrations. Accordingly, the treatment of these wastewaters is important before discharging them into the ecosystem. The photodegradation of IBP with TiO2 co-doped with functionalized CNTs (CNT-COOH and CNT-COCl) and urea, named as N-doping CNT/TiO2, irradiated with visible light of 410 nm was investigated in this study. The titanium tetrachloride was used as the precursor of Ti. The N-doping CNT-COCl/TiO2 photocatalysts exhibited a better crystalline structure and smaller crystal size than the N-doping CNT-COOH/TiO2 photocatalyst. It might largely ascribe to strong binding between acyl chloride functional group and TiO2. About 85.0%-86.0% of IBP was degraded with N-doping CNT/TiO2 within 120 min at natural condition, which obeyed the pseudo first order reaction and the rate constant was 4.45 × 10(-3)-1.22 × 10(-2) min(-1) and 5.03 × 10(-3)-1.47 × 10(-2) min(-1) for N-doping CNT-COOH/TiO2 and N-doping CNT-COCl/TiO2, respectively. The best IBP degradation of 87.9%-89.0% was found at pH 5, which indicated superoxide radicals (O2(-)) played a key role. The optimal pH was majorly dominated by the nature of IBP and N-doping CNT/TiO2. A successful synergy effect of TiO2 and dopants was exhibited and this mainly attributed to the strong binding strength by functional group of acyl chloride (COCl) and carboxylic acid (COOH). In summary, IBP could be effectively photodegraded by the fabricated N-doping CNT/TiO2 photocatalysts.