Search

Traditionally, direct-reading instruments have been used to directly determine the concentrations of indoor air pollutants that may exceed the regulation limits. However, these instruments cannot directly assess the potential health hazards of these pollutants to humans. In this study, we developed and improved a bacterial reverse mutation assay (Ames test) by using a direct gas exposure module to directly determine the mutagenicity of indoor air quality using five tester bacterial strains (TA98, TA100, TA102, TA1535, and TA1537). Thereafter, the module was used to evaluate the effects of exposure time, different concentrations of HCHO or toluene, and mutagenic activities. We found that TA100 was the most sensitive strain and was reverted by relatively lower concentrations of 0.035 ppm HCHO. Furthermore, 50 ppm of toluene exposures caused a significant increase in the number of revertant colonies of TA100 without S9 activation at the 1.5-8-h exposure time intervals. Our findings provide new evidence that gaseous HCHO exposure could display weak but direct, time-dependent, and dose-dependent mutagenic activities. The weak, direct-acting, indirect-acting, and time-dependent mutagen of 50 ppm toluene was also confirmed. Moreover, our improved Ames module and the exposure conditions provided in this study can be further applied to evaluate the mutagenicity of indoor air quality.

Lactoferrin (LF) is a multifunctional protein found in mammals, and it shows broad-spectrum antimicrobial activity. To improve the functional properties of specific probiotics in order to provide both the beneficial characteristics of lactic acid bacteria and the biological activity of LF, cDNAs of bovine LF (BLF), human LF (HLF), or porcine LF (PLF) were cloned into a nisin-inducible plasmid. These were then transformed into the selected eight probiotics, which are LF-resistant hosts. Expression of recombinant LFs (rLFs) was analyzed via SDS-PAGE and Western blot analysis. Although the selected host strains may not contain the nisRK genes (NisK, the sensor kinase, NisR, the regulator protein), the components of autoregulation, a low level of LFs expression can be successfully induced by using nisin within bacterial cells in a time-dependent manner in three engineered clones, including Lactobacillus delbrueckii/HLF, L. delbrueckii/BLF, and L. gasseri/BLF. Lactobacillus delbrueckii and Lactobacillus gasseri originate from yogurt and human milk, respectively, and both strains are functional probiotic strains. Therefore, we further compared the antibacterial activities of disrupted recombinant probiotic clones, conventional strains (host control), and vector control ones by using agar diffusion and broth inhibition analysis, and the expression of rLFs in the above three clones considerately improved their antibacterial efficacies against four important food-borne pathogens, namely, Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, and Salmonellaenterica. In conclusion, this study provides a simple strategy for the production of functional LFs (BLF and HLF) in both functional and LF-resistant hosts for applications in the field.

Biomass burning episodes are critical particulate matter (PM) issues in Taiwan. The occurrence patterns of biomass burning events through long-term PM monitoring are worth further exploration. This study monitored PM10, PM2.5, and black carbon (BC) over one year in central Taiwan. The source apportionment of BC was examined using light absorption techniques and divided into fossil fuel combustion (BCf) and biomass burning (BCb). The monitoring results showed that the annual average PM10, PM2.5, and BC mass concentrations were 45.4 μg/m3, 19.8 μg/m3, and 0.79 μg/m3, respectively, while the annual average ratio of BC/PM2.5 was 0.044. Furthermore, BCf was remarkably higher than BCb, accounting for 89% of the total BC mass. However, it was noticed that biomass burning smoke impacted the air quality by enhancing PM10, PM2.5, and BCb over monitoring location. There were 14.4% of hourly PM10 events (≥125 μg/m3) and 10.0% of hourly PM2.5 events (≥35 μg/m3) resulting from biomass burning episodes at this monitoring site in one-year observation. The hourly average PM10 and PM2.5 concentrations during these biomass burning episodes were 2.1 and 2.3 times higher than the annual average PM10 and PM2.5 concentrations. During severe biomass burning episodes, high levels of human carcinogens, such as 1, 3-butadiene, benzene, and isoprene were also observed. The results demonstrate that air quality is severely degraded during biomass burning episodes. Therefore, further research is required to understand the effects of biomass burning events on the residents' acute and chronic health conditions.

Iron and steel industry is crucial for economic development. However, large exhaust volume and complex feeding of the steel-making process results in enormous emissions of air pollutants such as particulate matter (PM), sulfur oxides (SOx), nitrogen oxides (NOx), polycyclic aromatic hydrocarbon (PAHs) and carbon monoxide (CO). This study sampled and analyzed the concentrations of PM, PAHs, SOx, NOx and CO at the inlet and outlet of the air pollution control devices (APCDs) adopted in sintering process (SP) and electric arc furnaces (EAF), respectively, to evaluate the performance of APCDs and emission characteristics of these air pollutants. The results show that filterable PM (FPM) concentrations measured at stacks of SP and EAF are 8.2 ± 1.3 and 13.6 ± 2.2 mg Nm–3, respectively. The FPM2.5 concentrations emitted from SP and EAF are 1.8 ± 0.5 and 3.2 ± 1.1 mg Nm–3, respectively, while the condensable PM (CPM) concentrations emitted from SP and EAF are measured as 37.7 ± 1.3 and 3.4 ± 0.8 mg Nm–3, respectively. Moreover, the flue gas desulfurization (FGD) and selective catalytic reduction (SCR) equipped in SP removed 82% and 58% of SOx and NOx, respectively, whereas SOx and NOx emitted from EAF are relatively low (< 1 ppm). The overall PAH removal efficiencies achieved with the APCDs adopted by SP and EAF are 72% and 26%, respectively. For total toxicity equivalency quantity (TEQ) PAH concentrations, similar results for SP (5.45 µg-BaPeq Nm–3) and EAF (4.74 µg-BaPeq Nm–3) are obtained. Moreover, the diagnosis ratios of FL/CHR, FL/(BaA + CHR), Pyr/5-MC and Pyr/(BaA + CHR) are suggested as the indicators for EAF. The emission factors calculated indicate that operating conditions of the APCDs in the SP investigated are well controlled. The concentrations of air pollutants emitted from SP investigated are lower than other studies. On the other hand, the concentrations of FPM and PM2.5 emitted from EAF are higher than other studies. However, NOx, SOx and PAHs are well controlled. Moreover, the CO emission factors calculated from these two steel-making processes are higher than most reports. Overall, the operation of APCDs should be improved to reduce air pollutants emitted from these two steel-making processes.

Commercial adsorbents – zeolite, granular activated carbon (GAC), and activated carbon fiber (ACF) – were modified with various alkaline agents – NaOH, K 2 CO 3 , diethanolamine (DEA), 2-amino-2methyl-1-propanol (AMP), and monoethanolamine + AMP (MEA + AMP) – to improve CO 2 adsorption. The CO 2 adsorption capacities and heat of adsorption of various adsorbents were studied using thermogravimetry/differential scanning calorimetry (TG/DSC). The CO 2 adsorption capacity of the original adsorbents was in the order zeolite > ACF > AC. The CO 2 adsorption capacities of AC, ACF, and zeolite modified with NaOH and K 2 CO 3 were higher than capacities of those modified with the other compounds. The CO 2 adsorption capacity of zeolite–K 2 CO 3 was the highest. Zeolite modified with alkaline agents provided weak adsorption sites for CO 2 because of the decrease in the adsorption heat. Therefore, zeolite has a suitable pore volume and mesoporous structure for use as a support for loading inorganic alkaline agents for CO 2 capture.

Incineration flue gas contains polycyclic aromatic hydrocarbons (PAHs) and sulfur dioxide (SO2). The effects of SO2 concentration (0, 350, 750, and 1000 ppm), reaction temperature (160, 200, and 280 degrees C), and the type of activated carbon fibers (ACFs) on the removal of SO2 and PAHs by ACFs were examined in this study. A fluidized bed incinerator was used to simulate practical incineration flue gas. It was found that the presence of SO2 in the incineration flue gas could drastically decrease removal of PAHs because of competitive adsorption. The effect of rise in the reaction temperature from 160 to 280 degrees C on removal of PAHs was greater than that on SO2 removal at an SO2 concentration of 750 ppm. Among the three ACFs studied, ACF-B, with the highest microporous volume, highest O content, and the tightest structure, was the best adsorbent for removing SO2 and PAHs when these gases coexisted in the incineration flue gas. Implications: Simultaneous adsorption of sulfur dioxide (SO2) and polycyclic aromatic hydrocarbons (PAHs) emitted from incineration flue gas onto activated carbon fibers (ACFs) meant to devise a new technique showed that the presence of SO2 in the incineration flue gas leads to a drastic decrease in removal of PAHs because of competitive adsorption. Reaction temperature had a greater influence on PAHs removal than on SO2 removal. ACF-B, with the highest microporous volume, highest O content, and tightest structure among the three studied ACFs, was found to be the best adsorbent for removing SO2 and PAHs.

Incinerator bottom ash contains a large amount of silica and can hence be used as a silica source for the synthesis of mesoporous silica materials. In this study, the conditions for alkaline fusion to extract silica from incinerator bottom ash were investigated, and the resulting supernatant solution was used as the silica source for synthesizing mesoporous silica materials. The physical and chemical characteristics of the mesoporous silica materials were analyzed using BET, XRD, FTIR, SEM, and solid-state NMR. The results indicated that the BET surface area and pore size distribution of the synthesized silica materials were 992 m2/g and 2-3.8 nm, respectively. The XRD patterns showed that the synthesized materials exhibited a hexagonal pore structure with a smaller order. The NMR spectra of the synthesized materials exhibited three peaks, corresponding to Q(2) [Si(OSi)2(OH)2], Q(3) [Si(OSi)3(OH)], and Q(4) [Si(OSi)4]. The FTIR spectra confirmed the existence of a surface hydroxyl group and the occurrence of symmetric Si-O stretching. Thus, mesoporous silica was successfully synthesized from incinerator bottom ash. Finally, the effectiveness of the synthesized silica in removing heavy metals (Pb2+, Cu2+, Cd2+, and Cr2+) from aqueous solutions was also determined. The results showed that the silica materials synthesized from incinerator bottom ash have potential for use as an adsorbent for the removal of heavy metals from aqueous solutions.

Few studies have investigated the use of activated carbon fibers (ACFs) impregnated with noble metals for the catalytic oxidation of volatile organic compounds (VOCs). This study determined the removal efficiency of toluene as a function of time over ACF-supported metal catalysts. Two catalysts (Pt and Pd), five reaction temperatures (120, 150, 200, 250, and 300°C), and three oxygen contents (6%, 10%, and 21%) were investigated to determine the removal of toluene. To study the effects of the characteristics of the catalysts on toluene removal, the composition and morphology of the ACFs were analyzed using the BET, XPS, ICP, and FE-SEM. The results showed that the 0.42%Pd/ACFs showed greater activity for toluene removal than did 2.68%Pt/ACFs at a reaction temperature of 200°C and an oxygen content of 10%. The main removal mechanism of toluene over the 2.68%Pt/ACFs at reaction temperatures less than 200°C was adsorption. The long-term catalytic activity of the 2.68%Pt/ACFs for toluene removal at a reaction temperature of 250°C and an oxygen content of 10% could be obtained. Furthermore, toluene removal over the 2.68%Pt/ACFs at 200°C could be enhanced with increasing oxygen content.

Many of the factors influencing the adsorption of volatile organic compounds by activated carbon fibers (ACFs) have been widely studied. However, most of them were investigated at low concentrations (500 ppm or less) and at low adsorption temperatures (lower than 100 °C). This study was to determine simultaneously the oxidation and adsorption of toluene onto activated carbon fibers (ACFs) at high concentration and high adsorption temperatures. We tested three ACFs, four inlet concentrations of toluene (700, 1,200, 1,600, and 2,000 ppm), and four adsorption temperatures (25, 50, 75, and 200 °C). The composition and morphology of the ACFs were also analyzed using BET, FTIR, EA, and FESEM. The results indicated that the best toluene adsorption capacity was for 569 mg/g ACFs at a toluene concentration of 1,200 ppm and at 25 °C. A combination of low O content and high mesopore volume was desirable for ACFs with a high toluene adsorption capacity at high toluene concentrations. Moreover, the breakthrough time decreased with increasing toluene concentration, and the adsorption capacity of toluene increased significantly when the inlet concentration of toluene increased to 1,200 ppm. The data also indicated that the breakthrough time and the adsorption capacity of toluene decreased with increasing adsorption temperature. The outlet concentration of toluene did not reach 1,200 ppm when adsorption was saturated at 200 °C, as the oxygen functional groups on the ACF surface had reacted with toluene to form other compounds.

The effects of different calcination temperatures (300, 400 and 500 °C) and copper loading (1, 3 and 5 wt.%) on the properties of the copper supported on activated carbon (AC) were investigated along with the catalytic activity of NO reduction. The results showed that the properties and copper species of Cu/AC catalysts were significantly affected by calcination temperature and copper loading. The NO reduction of the Cu/AC-300 catalysts with different copper loading follows the order 5Cu/AC-300 > 3Cu/AC-300 > 1Cu/AC-300. However, the NO reduction increased insignificantly when the loading of copper exceeds 3 wt.%. Choosing 3Cu/AC-300 as a catalyst in NO reduction is more economical than other catalysts. Moreover, the catalyst calcined at 300 °C showed the highest activity with 52.9% NO reduction in 6% O2 at 275 °C. The good dispersion of the copper particles and the species of CuO and Cu2O that existed in 3Cu/AC-300 catalysts were the determinant parameters for NO reduction. The optimum reaction conditions for NO reduction were identified as 6% O2 at 275 °C with 0.2 g of catalyst.

This study investigates the emission characteristics of CO(2), SO(2) and NOx in the flue gas of coal combustion by varying the compositions and concentrations of feed gas (O(2)/CO(2)/N(2)) and the ratios of recycled flue gas. The differences between O(2)/recycled flue gas (O(2)/RFG) combustion and general air combustion are also discussed. Experimental results indicate that the maximum concentration of CO(2) in O(2)/CO(2) combustion system is 95% as the feed gas is 30% O(2)/70% CO(2). The average concentration of CO(2) in the flue gas of O(2)/CO(2) coal combustion system is higher than 90% and much higher than that of O(2)/N(2) coal combustion system. This high concentration of CO(2) is beneficial for the separation of CO(2) from the flue gas by adsorption or absorption technologies. The maximum concentration of CO(2) in O(2)/N(2) combustion system is only 34% at the feed gas 50% O(2)/50% N(2), the concentration of CO(2) is increased with the concentration of O(2) in feed gas. By O(2)/CO(2) combustion technology, higher concentration of SO(2) is produced as the feed gas is 30% O(2)/70% CO(2) or 40% O(2)/60% CO(2), while higher concentration of NOx is produced as the feed gas is 20% O(2)/80% CO(2) or 50% O(2)/50% CO(2). The mass flow rates of CO(2), SO(2) and NOx in the flue gas are all increased with the ratio of recycled flue gas except for the feed gas 20% O(2)/80% CO(2). The enhanced mass flow rates of air pollutants in such O(2)/RFG combustion system are also beneficial for improving the control efficiencies of air pollution control devices. By O(2)/N(2) combustion technology, higher concentrations of SO(2) and NOx are produced as the feed gas is 21% O(2)/79% N(2). The results also indicate that the formation of NOx in general air combustion system is higher than that in O(2)/RFG or O(2)/CO(2) combustion system.

The purpose of this research was to simultaneously evaluate the removal efficiency of acid gases and PAHs from the flue gas emitted by a laboratory incinerator. This flue gas contained dust, acid gases, organics and heavy metals. A spray dryer combined with a fabric filter was used as the air pollution control device (APCD) in this study. The operating conditions investigated included different feedstock additives (polyvinyl chloride (PVC) and NaCl) and spray dryer additives (SiO2, CaCl2 and NaHCO3). The removal efficiency for SO2 could be enhanced by adding inorganic additives, such as SiO2, CaCl2 and NaHCO3. The presence of PVC in the incinerator feedstock also increased the removal efficiency of SO2in the spray dryer. The improved removal of PAHs could be attributed to the addition of feedstock additives (PVC and NaCl) and spray dryer additives (SiO2, CaCl2 and NaHCO3).

Few studies have investigated the use of activated carbon fibres (ACFs) impregnated with metal oxides for the catalytic oxidation of volatile organic compounds (VOCs). Thus, the effects of the ACF-supported metal oxides on toluene removal are determined in this study. Three catalysts, namely, Ce, Mn, and Cu, two pretreatment solutions NaOH and H2O2, and three reaction temperatures of 250°C, 300°C, and 350°C, were employed to determine toluene removal. The composition and morphology of the catalysts were analysed using Brunauer–Emmett–Teller (BET), transmission electron microscope (TEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectrometer (FTIR), and thermo-gravimetric analyser (TGA) to study the effects of the catalyst's characteristics on toluene removal. The results demonstrated that the metal catalysts supported on the ACFs could significantly increase toluene removal. The Mn/ACFs and Cu/ACFs were observed to be most active in toluene removal at a reaction temperature of 250°C with 10% oxygen content. Moreover, the data also indicated that toluene removal was slightly improved after pretreating the ACFs with NaOH and H2O2. The results suggested that surface-metal loading and the surface characteristics of the ACFs were the determinant parameters for toluene removal. Furthermore, the removal of toluene over Mn/ACFs-H2O2 decreased when the reaction temperature considered was>300°C.

Previous studies have shown that pollutants from incineration include heavy metals, organic compounds, particulate and acid gas. However, most studies on a single pollutant, it is rare for a study to concentrate on all possible pollutants and the relations between these pollutants under various incineration conditions. The objective of this work was to experimentally study the effect of different operating conditions on the pollutants emitted during incineration and the relations between these pollutants. The operating conditions of the experiments included the temperature of the combustion chamber and the species of organics. The findings indicated that the concentration of hydrogen chloride (HCl) in the presence of polyvinyl chloride (PVC) was higher than that of sodium chloride (NaCl). Regardless of what Cl-containing feedstock was added, the concentration of chromium (Cr) was constant. When organic chloride was added, Cr was the main metallic element which influenced the formation of polycyclic aromatic hydrocarbons (PAHs). On the other hand, when inorganic chloride (NaCl) was added, lead (Pb) was the major element.

SBA-15 materials were synthesized through the hydrothermal method. The SBA-15 prepared at the hydrothermal time of 24 h possessed a higher surface area and a good hexagonal structure, so it was used as the catalytic support in this experiment. The base metals (Cu, Co, Ni) coated on SBA-15 were prepared for toluene removal. The results revealed that the catalytic activity of Cu/SBA-15 for toluene removal was about 70% at 250 °C, which was the best among the three catalysts. The modification of Cu/SBA-15 by adding different transition metals (Ce, Co, Ni, Mn) to improve the removal efficiency of toluene and NO was also investigated in this study. The results indicate that the catalytic activity of Mn–Cu/SBA-15 for toluene removal was about 100% at 250 °C. The toluene as a reductant on the removal of NO was also determined. Furthermore, the catalytic activity of Mn–Cu/SBA-15 for NO removal can reach about 70% at 300 °C when toluene is used as reductant.

The objective of this research was to evaluate the reaction characteristics of Ca(OH) 2 , HCl and SO 2 in the flue gas emitted by a laboratory incinerator. The amount of sulfur retained in the residues (including the spray dryer ash and baghouse ash) was also evaluated in this study. The experimental parameters included HCl concentration (500–2000 ppm), SO 2 concentration (500–2000 ppm), relative humidity (40–80% RH), and the addition of CaCl 2 (30 wt.%). The results indicated that an HCl concentration of 500–2000 ppm did not affect HCl removal efficiency in the spray dryer at 150 °C and 45±5% RH. On the other hand, increase in SO 2 concentration from 500 to 2000 ppm enhanced SO 2 removal at 150 °C and 75±5% RH. Moreover, increase in removal efficiency of SO 2 was more obvious when the relative humidity was greater than 80%. When the flue gas contained both HCl and SO 2 simultaneously, the removal efficiency of SO 2 could increase from 56.7 to 90.33% at HCl concentration of 236 ppm. However, when the concentration of HCl exceeded 535 ppm, the removal efficiency of SO 2 decreased with increasing concentration of HCl. The removal efficiency of SO 2 could be increase to 97.7% with the addition of CaCl 2 .