Co-pyrolysis of fly ash with sewage sludge for PCDD/F removal.

Fly ash generated from municipal waste incineration (MWI) contains various toxic substances, and it has to be properly treated before disposal or reuse. Water washing and thermal pyrolysis can improve the destruction efficiency of PCDD/Fs in fly ash generated from municipal solid waste incinerators. Since sulfur oxides and nitrogen compounds generated by the heating of the sewage sludge poison the catalytic active sites for PCDD/Fs formation on fly ash surface, co-pyrolysis of fly ash with sewage sludge effectively inhibits precursor formation and de novo synthesis reaction, resulting in the great reduction of PCDD/F formation. The results of the pyrolysis at 350 °C show that the PCDD/Fs removal efficiencies based on mass concentration are over 99%. The results at 350 °C of different reaction times show that the reaction time of 10 min is sufficient to reach the European End of Waste criteria (≤ 20 pg TEQ/g) when the ratio of fly ash/sewage sludge is controlled at 1:1.

Ozone catalytic oxidation of toluene over triple perovskite-type catalysts modified with KMnO4.

A unique triple perovskite-type catalyst was successfully synthesized using the simple sol-gel approach, and surface acid modification was added to improve the ozone catalytic oxidation (OZCO) process ability to remove toluene more effectively. Our study indicates that La3MnCuNiO9 catalyst treated with KMnO4 shows the best toluene oxidation activity. At 250 °C, the rates of conversion and mineralization were 100% and 83%, respectively, under thermal catalytic system when C7H8 concentration = 500 ppm. During the OZCO system ([C7H8] = 20 ppm, O3/C7H8=8; room temperature), for 6 h, the conversion rate remained at 100%. The high ratios of Mn4+/(Mn4++Mn3+), Cu2+, and abundant surface oxygen species, high specific surface area, and pore volume lead to remarkable catalytic performance of this catalyst. Meanwhile, the catalyst contributes to superior stability and water resistance. The catalytic mechanism of La3MnCuNiO9 after KMnO4 treatment in the context of OZCO was further discussed. Overall, after KMnO4 treatment, the La3MnCuNiO9 catalyst reveals extraordinary catalytic activity and excellent stability combination of this catalyst with ozone exhibits high toluene removal efficiency in the OZCO system and has a good potential for industrial applications.

Ozone catalytic oxidation of low-concentration formaldehyde over ternary Mn-Ce-Ni oxide catalysts modified with FeOx.

Manganese oxide-based catalysts have attracted extensive attention due to their relatively low cost and remarkable performance for removing VOCs. In this research, we used the Pechini method to synthesize manganese-cerium-nickel ternary oxide catalysts (MCN) and evaluated the effectiveness of catalytic destruction of formaldehyde (HCHO) and ozone at room temperature. FeOx prepared by the impregnation method was applied to modify the catalyst. After FeOx treatment, the catalyst represented the best performance on both HCHO destruction and ozone decomposition under dry conditions and exhibited excellent water vapor resistance. The as-prepared catalysts were next characterized via H2-temperature programmed reduction (H2-TPR), temperature programmed desorption of O2 (O2-TPD), and X-ray photoelectron spectroscopy (XPS), and the results demonstrated that addition of FeOx increased Mn3+ and Ce3+ concentrations, oxygen vacancies and surface lattice oxygen species, facilitated adsorption, and redox properties. Based on the results of in situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS), possible mechanisms of ozone catalytic oxidation of HCHO were proposed. Overall, the ternary mixed-oxide catalyst developed in this study holds great promise for HCHO and ozone decomposition in the indoor environment.

Modifying α-Al2O3 with cerium, zirconium, and sulfate for catalytic removal of C4F8.

Modification of α-Al2O3 (A) with cerium (C), zirconium (Z), and sulfate (S) for effective C4F8 removal is evaluated at temperatures ≤ 650 °C. Catalytic hydrolysis of C4F8 is conducted to compare the performance of catalysts prepared (namely, A, AC, AZ, AS, ACS, and AZS). The interplay between rare earth element, acid amount, and surface area is further investigated. An investigation was carried out by characterization of catalysts by using XRD, BET, and NH3-TPD. XRD pattern of the modified α-Al2O3 catalyst shows that the average grain size is 37 nm. BET analysis indicates that the surface area increases with the addition of Ce and Zr, while NH3-TPD analysis shows the improvement of acid sites after the addition of Ce, Zr, and SO42-. The experimental results indicate that C4F8 conversion over A catalyst reaches 14.81% at 550 °C with the addition of 38% H2O(g). Under the same operating condition, C4F8 conversion efficiencies achieved with AC and AZ catalysts increase to 42.03% and 50.1%, respectively. Furthermore, the efficiencies over AS, ACS, and AZS catalysts increase to 49.85%, 86.94%, and 87.18%, respectively. Stability tests show that the performances of the catalysts for C4F8 conversion are with the order of AZS > ACS > AZ > AC > AS > A at 650 °C during 24 h. The activation energy of the AZS catalyst in catalytic hydrolysis of C4F8 is 60.49 kJ/mol. The products of C4F8 conversion mainly include CO2, CO, and COF2 and small amounts of CHF3 and C2F4. This study has confirmed that the AZS catalyst shows the best activity, acidity, and stability on C4F8 removal.

Characteristics of polycyclic aromatic hydrocarbons in ambient air of a tropical mega-area, Ho Chi Minh City, Vietnam: concentration, distribution, gas/particle partitioning, potential sources and cancer risk assessment.

This is the first investigation on overall characteristics of 25 polycyclic aromatic hydrocarbons (PAHs) (15 PAHs regulated by US-EPA (excluding naphthalene) and 16 PAHs recommended by the European Union) in ambient air of Ho Chi Minh City, Vietnam. Their levels, congener profiles, gas/particle partitioning, potential sources of atmospheric PAHs (gas and particulate phases), and lung cancer risks in the dry and rainy seasons were examined. The ∑25 PAH concentration in the dry and rainy seasons ranged from 8.79 to 33.2 ng m-3 and 26.0 to 60.0 ng m-3, respectively. Phenanthrene and Indeno[123-cd]pyrene were major contributors to gaseous and particulate PAHs, respectively, while benzo[c]fluorene was dominant component of the total BaP-TEQ. The ∑16 EU-PAH concentration contributed to 13 ± 2.7% of the total ∑ 25 PAH concentration; however, they composed over 99% of the total ∑ 25 PAH toxic concentration. Adsorption mainly governed the phase partitioning of PAHs because the slope of correlation between logKp and logP0L was steeper than - 1. Vehicular emission was the primary source of PAHs in two seasons; however, PAHs in the dry season were also originated from biomass burning. Assessment of lung cancer risk showed that children possibly exposed to potential lung cancer risk via inhalation.

Characteristics of PM and PAHs emitted from a coal-fired boiler and the efficiencies of its air pollution control devices.

Sampling and analysis of filterable particulate matter (FPM), FPM2.5, condensable particulate matter (CPM), polycyclic aromatic hydrocarbons (PAHs), sulfur oxides (SOx), and nitrogen oxides (NOx) emitted from a coal-fired boiler equipped with selective catalytic reduction (SCR)+ electrostatic precipitator (ESP) + wet flue gas desulfurization (WFGD) + wet electrostatic precipitator (WESP) as air pollution control devices (APCDs) are conducted. The results show that NOx concentration emitted from the coal-fired boiler is 56 ± 2.17 ppm (with the NOx removal efficiency of 47.2%), which does not meet the best available control technology (BACT) emission standard (≤ 30 ppm). On the other hand, the WFGD adopted has a good removal efficiency for SOx and HCl. Both SOx and HCl emission concentrations are < 1 ppm, and removal efficiencies are > 99%. The FPM and FPM2.5 emitted from the coal-fired boiler are 0.9 ± 0.06 mg/Nm3 and < 0.09 ± 0.006 mg/Nm3, respectively. The overall removal efficiency of FPM achieved with ESP+WFGD+WESP+MGGH is 99.98%. However, high concentration of CPM (37.4 ± 6.3 mg/Nm3) is measured, which is significantly higher than FPM and FPM2.5. The concentrations of 27 PAHs at the WESP inlet and stack are measured as 667 ng/Nm3 and 547 ng/Nm3, respectively while the removal efficiencies of gas- and solid-phase PAHs are 9% and 58%, respectively. The results show that APCDs adopted are not effective in removing PAHs (only 18%), and gas-phase PAHs contribute the most in the total PAH emission. In addition, the benzo(a)pyrene equivalent (BaPeq) concentration emitted from the stack is 28.8 ng-BaPeq/Nm3, and most of it is contributed by 4-6 ring PAHs with high toxic equivalent factors (TEFs). Furthermore, the emission factors of air pollutant emitted from coal-fired boilers equipped with different combinations of APCDs are compiled and compared. The results show that except for CPM and NOx, the emission factors of air pollutant calculated for this coal-fired boiler are lower if compared with other studies.Implications: Primary particles discharged from coal-fired processes include filterable particulate matter (FPM) and condensable particulate matter (CPM). PM2.5 emissions would be greatly underestimated if CPM is ignored. Polycyclic aromatic hydrocarbons (PAHs) are semi-volatile organic compounds (SVOCs) formed by two or more fused benzene rings. PAHs have attracted much public attention because of toxicity and carcinogenicity. This study selects one coal-fired boiler with the best available control technology (BACT) to simultaneously measure the concentrations of PM, PAHs, and gaseous pollutants at the inlet and outlet of air pollution control devices (APCDs) to understand the efficacy of APCDs adopted and pollutant emission intensity.

Application of thermal desorption for measuring PAHs on PM2.5.

PM2.5 and polycyclic aromatic hydrocarbons (PAHs) emitted from various sources may cause respiratory disease and lung cancer. Additionally, PAHs deposited on PM2.5 would aggravate the hazard to human health once inhaled. Therefore, it is essential to investigate the PAHs adsorbed on PM2.5 in ambient air. However, analysis of PAHs on PM2.5 is limited so far due to high detection limit of the analytical method and complex pretreatment procedures of the sample. In this study, thermal desorption (TD) is combined with GC-HRMS for direct analysis of PAHs on PM2.5 collected by the filter without pretreatment. The results indicate that distribution of PAHs on the filter is uniform and each filter section is representative for direct analysis of PAHs on PM2.5. The optimal thermal desorption temperature and purge time of analysis are found at 320°C and 60 s, respectively. Furthermore, the PAHs on PM2.5 of ambient air in Taiwan including traffic area, industrial area, suburban area, and background site are investigated. The results indicate that the concentrations of PAHs on PM2.5 in ambient air of Northern, Central, and Eastern Taiwan are in the range of 0.13-6.63 ng/m3, with an average concentration of 2.23 ng/m3. The PAH concentration measured in winter is significantly higher than that in summer, and the concentration of PAHs on PM2.5 ranges from 0.071 to 0.280 ng/µg while the average concentration is 0.133 ng/µg. The technology optimized in this study can be applied for rapid and accurate measurement of PAHs present on fine particles.

Application of plasma catalysis system for C4F8 removal.

Octafluorocyclobutane (C4F8) with a GWP100 (global warming potential) of 10,000 times of CO2 is listed as potent greenhouse gas. Therefore, development of effective control technologies for reducing C4F8 emissions has become an emerging issue to be addressed. In this study, decomposition of C4F8 was investigated via three systems including catalytic hydrolysis, non-thermal plasma, and plasma catalysis, respectively. Decomposition of C4F8 achieved with catalytic hydrolysis reaches the highest efficiency of 20.1%, being obtained with γ-Al2O3 as catalyst in the presence of 10% H2O(g) and operating temperature of 800 °C. For plasma-based system, the highest C4F8 conversion obtained with non-thermal plasma is 62% at a voltage of 23 kV. As for the plasma catalysis system, 100% C4F8 conversion efficiency can be achieved at an applied voltage of 22-23 kV. The effects of various parameters such as gas flow rate and C4F8 concentration on plasma-based system show that the plasma catalysis also has better resistivity for the high gas flow rate. The highest energy efficiency of 0.75 g/kWh is obtained for the gas flow rate of 500 mL/min, with the C4F8 conversion of 41%. The highest conversion 89% was achieved with the O2 content of 0.5%. Addition of Ar improves the performance of plasma-based system. When Ar is controlled at 20%, C4F8 conversions obtained with plasma catalysis reach 100% at applied voltage of 22-23 kV even in the presence of 5% O2. The main products of the C4F8 conversion include CO2, NOx, and COF2 when O2 is added into the system. As water vapor is added, HF is also formed. This study has confirmed that combined non-thermal plasma with catalyst system to convert C4F8 is indeed feasible and has good potential for further development.

Emissions of PAHs, PCDD/Fs, dl-PCBs, chlorophenols and chlorobenzenes from municipal waste incinerator cofiring industrial waste.

Concentrations and distributions of PAHs and chlorinated aromatic compounds including PCDD/Fs, dl-PCBs, chlorophenols (CPs), and chlorobenzenes (CBz) in the municipal waste incinerator are investigated to characterize their formation and emission via intensive stack sampling. In addition, the toxicity of fly ash contribution by PCDD/Fs and dl-PCBs is evaluated in this study. The results reveal that concentrations of PCDD/Fs and dl-PCBs in flue gas are significantly lower than those of CPs, CBz, and PAHs. Additionally, the removal efficiencies of PAHs and chlorinated aromatic compounds achieved with existing air pollution control devices are evaluated, indicating that the removal efficiencies achieved with activated carbon injection + baghouse (95-99%) are higher than those with semi-dry scrubber (SDS). Besides, PCDD/Fs and PCBs TEQ concentrations in SDS and BH ashes are within 1.61-2.66 WHO-TEQ/g and 0.09-0.19 WHO-TEQ/g, respectively. Furthermore, the calculated mass flow rates suggest that the input rate of PCDD/Fs and dl-PCBs of SDS are 60.24 mg/h and 59.74 mg/h, respectively. The mass flow rates of PCDD/Fs and dl-PCBs after SDS in flue gas are 32.47 mg/h and 49.73 mg/h, respectively. However, the discharge rates of PCDD/Fs and dl-PCBs from SDS are 120.60 mg/h and 27.05 mg/h, respectively, indicating that PCDD/Fs are significantly formed within the SDS. PCDD/Fs formation is attributed to the operating temperature of SDS (240 ± 11.5 °C), which is within the temperature window for de novo synthesis. Thus, operating parameters of the APCDs should be optimized to reduce the formation of PAHs and chlorinated aromatic pollutants from MWI.

Characteristics of PCDD/Fs in PM2.5 from emission stacks and the nearby ambient air in Taiwan.

This study aimed to find the characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in fine particulate matter from different stationary emission sources (coal-fired boiler, CFB; municipal waste incinerator, MWI; electric arc furnace, EAF) in Taiwan and the relationship between PM2.5 and PM2.5-bound PCDD/Fs with Taiwanese mortality risk. PM2.5 was quantified using gravimetry and corresponding chemical analyses were done for PM2.5-bound chemicals. Mortality risks of PM2.5 exposure and PCDD/Fs exposure were calculated using Poisson regression. The highest concentration of PM2.5 (0.53 ± 0.39 mg/Nm3) and PCDD/Fs (0.206 ± 0.107 ng I-TEQ/Nm3) was found in CFB and EAF, respectively. Higher proportions of PCDDs over PCDFs were observed in the flue gases of CFB and MWI whereas it was reversed in EAF. For ambient air, PCDD/F congeners around the stationary sources were dominated by PCDFs in vapor phase. Positive matrix factorization (PMF) analysis found that the sources of atmosphere PCDD/Fs were 14.6% from EAF (r = 0.81), 52.6% from CFB (r = 0.74), 18.0% from traffic (r = 0.85) and 14.8% from MWI (r = 0.76). For the dioxin congener distribution, PCDDs were dominant in flue gases of CFB and MWI, PCDFs were dominant in EAF. It may be attributed to the different formation mechanisms among wastes incineration, steel-making, and coal-burning processes.

Emission characteristics of dl-PCNs, PCDD/Fs, and dl-PCBs from secondary copper metallurgical plants: Control technology and policy.

This study investigated the characteristics of dl-PCNs, PCDD/Fs and dl-PCBs emitted from two typical secondary copper metallurgical plants processing copper sludge equipped with different sets of air pollution control devices (APCDs). Results indicated that the emission factors of dl-PCNs and PCDD/Fs of plant A are 0.00775 and 1.09 µg TEQ/ton, respectively, which are remarkably lower than those of plant B (3.12, 181 and 25.5 µg TEQ/ton for dl-PCNs, PCDD/Fs and dl-PCBs, respectively). Dl-PCNs contributed 0.7-2.7% of total TEQ for flue gases and up to 2.6% of TEQ for ash samples. The TEQ concentration of dl-PCNs in fly ash individually exceeds the regulated level of 1 ng TEQ/g regulated by Taiwan EPA, indicating that emission and discharge of dl-PCNs should be regulated. The combination of semidry scrubber and activated carbon injection (ACI) + baghouse (BH) is effective for simultaneous removals of dl-PCNs and PCDD/Fs in plant A; while the combination of cyclone, secondary combustion chamber, ACI + BH and wet scrubber (WS) is not optimal for removing dl-PCNs, PCDD/Fs and dl-PCBs. Memory effect occurring within BH and WS is responsible for low removal efficiencies of these POPs in plant B. This study suggests appropriate APCDs for simultaneous removal of three POP groups and recommends the inclusion of dl-PCNs in emission standard.

Reduction of polychlorinated naphthalenes (PCNs) emission from municipal waste incinerators in Taiwan: Recommendation on control technology.

Emission factor and removal efficacy of PCNs are evaluated via the flue gas sampling of two MWIs equipped with different air pollution control devices (APCDs) in Taiwan. MWI-A is equipped with ESP, wet scrubber (WS) and selective catalytic reduction (SCR), while cyclone (CY), semi-dry absorber (SDA), activated carbon injection (ACI) and baghouse (BH) are employed in MWI-B. The average concentrations of PCNs measured at stacks of MWI-A and MWI-B are 2.1 ng Nm-3 (0.218 pg TEQ Nm-3) and 23.2 ng Nm-3 (0.425 pg TEQ Nm-3), respectively. The emission factors of PCNs calculated from feeding rates of waste and stack sampling results range from 6.7 to 6.95 µg t-1 (0.790-1.45 ng TEQ t-1). PCNs are formed in ESP via chlorination, while SCR and SDA + ACI + BH are effective in removing PCNs with the overall efficacies of 97.6% and 94.3%, respectively. PCN removal efficiencies achieved with SCR and SDA + ACI + BH increase as chlorination level increases. Specifically, around 72% and 82% of Mono-CN are removed by SCR and SDA + ACI + BH, respectively. The removal efficacies of other homologues achieved with SCR are consistently high (96-100%). Dominances of Mono-to Tri-CNs in scrubbing liquid collected from WS and higher removal efficacies of these homologues achieved with WS + ESP compared with ESP alone indicate that WS can capture low chlorinated PCNs to some extent. The results suggest that CY + SDA + ACI + BH should be equipped in MWI for effective removal of PCNs, while ESP, WS and SCR should be utilized with precaution to eliminate PCNs formation and enhance the PCNs removal efficiency.

Efficacy of the novel continuous sampling system for PCDD/Fs and unintentional persistent organic pollutants.

Long-term sampling is essential for monitoring the air pollutants emitted from stack since it can monitor the pollutants emission continuously including the stages of start-up, shutdown and normal operation. However, commercial continuous sampling equipment such as AMESA faces the challenges of high weight and complicated sampling procedures. This study has developed a long-term and automatic sampling system (National Central University continuous stack sampling system, NCU-CS3), and compared the efficiency with manual sampling train (MST). The results indicate that relative standard deviation (RSD) of PCDD/Fs concentrations measured between NCU-CS3 and MST is <20%, demonstrating that the difference between NCU-CS3 and MST in measuring PCDD/Fs is insignificant. Besides, the effects of adsorbent temperature, adsorbent amount and type of adsorbent on breakthroughs of PAHs and unintentional-persistent organic pollutants (UPOPs) such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), chlorinated phenols (CPs), chlorinated benzenes (CBs) and polychlorinated naphthalenes (PCNs) are evaluated. The results indicate that the breakthrough of pollutants increases with increasing temperature of XAD-2 and decreases with increasing XAD-2 amount. Moreover, XAD-4 is used as alternative adsorbent to test the breakthrough and the results indicate that the breakthroughs of UPOPs of XAD-4 as adsorbent are lower than that with XAD-2 due to higher specific surface area of XAD-4. Furthermore, the residual of PCDD/Fs with NCU-CS3 as the sampling train is relatively low (1.5-3.8%), which meets the regulation of EN 1948-5 (10%).

Evaluation of the effectiveness of nonthermal plasma disinfection.

As concern has increased regarding the interaction between efficiency and safety of disinfection, plasma becomes a viable alternative for disinfection in comparison with traditional methods. Dielectric barrier discharge (DBD) is applied to deactivate Bacillus subtilis and Escherichia coli , respectively, and disinfection efficiency is experimentally evaluated in this study. Tests are conducted with different working gases to investigate their effects on disinfection. Results show that Ar plasma diluted with 25% O2 enhances the germicidal effects to5.9 and 6.9 (log reduction) for B. subtilis and E. coli, respectively, and OES results show that active Ar and O species play important roles to weaken cell wall of microbes and further disinfect E. coli and B. subtilis. Analysis of protein and total sugar release indicates that active species such as ozone, NO and Ar* produced by plasma result in hydrolysis of the cell. In the meantime, charged particles produced by plasma would affect the amount of sugar released, resulting in different germicidal effects. Overall, plasma can disinfect microorganisms mainly via the generation of oxidising agents including ozone, NO and UV with a comparatively short treatment period, which is typically less than 5 min.

Characterization of PCN emission and removal from secondary copper metallurgical processes.

This study investigates the characteristics of PCN emission and removal from two secondary copper metallurgical processes (plants A and B) equipped with different air pollution control devices (APCDs). Different operating conditions and feeding materials result in varying emission factors of PCNs from two plants. The average PCN concentration emitted from plant B (7597 ng Nm-3) is significantly higher than that emitted from plant A (32.5 ng Nm-3) and those reported in China (5.8-2845 ng Nm-3). Similar trend is found for fly ash samples collected from two plants. Low chlorinated homologues (Mono-to Tri-CNs) are the major contributors to total PCNs measured in flue gas, fly ash and slag samples. Combination of semi-dry absorber, activated carbon injection and baghouse is effective for PCN removal in plant A, with the overall removal efficiency of 98%. The overall removal efficiency of PCNs achieved with APCDs equipped in plant B is 90%, however, increases of some homologues as the flue gases passing through baghouse and wet scrubber are found, suggesting the occurrence of memory effect within baghouse and wet scrubber.

Photocatalytic removal of trichloroethylene from water with LaFeO3.

Tricholorethylene (TCE) has been recognized as second common organic pollutant found in groundwater in Taiwan. Several advanced oxidation processes (AOPs) have been applied for TCE removal and photocatalytic is one of promising AOP techniques. In this study, LaFeO3 is successfully synthesized via sol-gel method and investigated for its photocatalytic oxidation rate toward TCE in water. Experimental results indicate that 95% removal efficiency of TCE can be achieved in aqueous solution with LaFeO3 (2 g/L) as photocatalyst within 1 h of Xenon lamp illumination. Additionally, the influences of initial TCE concentration, light intensity, photocatalyst loading, and pH value on the TCE removal efficiency are evaluated as well. The highest energy efficiency obtained in this study is 10.8 mg TCE/kWh and the value is higher than those reported in previous studies. Besides, removal mechanisms have been identified and the results indicate that the overall removal efficiency reaches 82%, with adsorption and photolysis accounting for 20% and 39%, respectively.

Photocatalytic oxidation of toluene and isopropanol by LaFeO3/black-TiO2.

Large amount of volatile organic compounds (VOCs) are emitted from industrial, mobile, and domestic sources, causing adverse effects on human health and environment. Among VOCs, toluene and isopropanol (IPA) are commonly used as solvent, soldering flux, and spray paint and their emissions need to be reduced. Several VOCs abatement technologies are available to reduce VOC emission and photocatalytic oxidation of VOC is regarded as a viable technique due to its advantage of utilizing solar energy. TiO2 has been investigated for its oxidation capability toward VOCs because of its good photocatalytic activity. However the utilization is limited to UV due to its wider bandgap; furthermore, its fast recombination rate of electron-hole pair reduces the oxidation rate of VOCs. Black-TiO2 and perovskite-type photocatalyst such as LaFeO3 can be applied to enhance photocatalytic activity due to narrower bandgap and longer electron-hole pair lifetime. In this study, black-TiO2 and LaFeO3 are prepared and investigated for their photocatalytic oxidation rates toward toluene and IPA. Results show that toluene removals achieved with black-TiO2 and LaFeO3 are 89% and 98% while IPA removals are 90% and 94%, respectively. Both photocatalysts show better photocatalytic activity than TiO2 and good absorption capability toward visible light. Graphical abstract.

Characterization of PCDD/Fs and dl-PCBs emission from combustion of PCB-containing oil in a fluidized-bed incinerator.

Emissions of PCDD/Fs and dl-PCBs from the combustion of PCB-containing oil in a hazardous waste incinerator are characterized. Flue gas samples are simultaneously taken at three points, including the outlet of ultrasonic wet scrubber, the outlet of heat exchanger and stack. In addition, solid matter samples including incinerator bottom ash, wet scrubber sludge, heat exchanger ash and baghouse ash are also collected. The results indicate that TEQ concentration (PCDD/Fs + dl-PCBs) measured in stack from the combustion of PCB-containing oil is 0.51 ng WHO-TEQ/Nm3. For the solid matter, PCDD/F and dl-PCB concentrations of baghouse ash and wet scrubber sludge are significantly higher than those measured in bottom and heat exchanger ashes. The total removal efficiencies of PCDD/Fs + dl-PCBs achieved with bag filtration (BF) + activated carbon injection (ACI) reaches 65.0%. The emission factors of PCDD/Fs and dl-PCBs from incinerating PCB-containing oil are 1.05 and 0.08 ng WHO-TEQ/L, respectively. The overall PCDD/Fs and dl-PCBs destruction efficiencies achieved with fluidized-bed incinerator reach 99.87% and 99.9998%, respectively, which demonstrates that incineration is an effective engineering practice for treating PCB-containing oil. Moreover, this is the first study suggesting the ratios of PCB-114/(PCB-126+ PCB-114) and PCB-157/(PCB-169+ PCB-157) as indicators to distinguish the emission source of dl-PCB from combustion process and technical mixture evaporation in diagnostic ratio analysis.

Plasma catalytic oxidation of toluene over double perovskite-type oxide via packed-bed DBD.

Various perovskite-type catalysts including La2CoMnO6, LaCoO3, and LaMnO3 are first evaluated for the activities toward C7H8 removal. Experimental results indicate that double-type La2CoMnO6 shows better activity if compared with single perovskites due to high lattice oxygen content and good reducibility. Subsequently, perovskite catalysts are combined with plasma (NTP) to form in-plasma catalysis (IPC) and post-plasma catalysis (PPC) systems. The results indicate that IPC systems have better higher performance than that of NTP-alone and PPC. Especially, high C7H8 conversion (100%) and mineralization efficiency (96.8%) can be achieved with the applied voltage of 18 kV and temperature of 120 °C when La2CoMnO6 is integrated with NTP to form IPC system. Also, it owns the highest energy efficiency (0.14 g/kWh). It is concluded that IPC performance for C7H8 removal is closely related with the properties of catalyst surface. In addition, the kinetics of IPC systems are investigated by a simplified model, and the result indicates that IPC with La2CoMnO6 as catalyst has a higher overall energy constant. This study reveals that double-type La2CoMnO6 is of higher activity than single perovskites for C7H8 removal, and demonstrates that double-type La2CoMnO6 is of high potential to form plasma catalysis system for VOCs removal.

Measurement of PCNs in sediments collected from reservoir and river in northern Taiwan.

Sediment samples were collected from a large reservoir and a river in northern Taiwan to investigate the occurrence and characteristics of Σ73PCNs analyzed. Results indicate that total concentrations of PCNs (Di- to Octa-CNs) measured in sediments collected in reservoir (29.2 ±â€¯7.11 pg/g-dw) are significantly lower than that of samples collected in river (987 ±â€¯440 pg/g-dw). The increasing trend of PCN concentration from upstream to downstream is found for the sediments collected in reservoir. PCN concentrations measured in surface sediments are relatively higher than that measured in sub-surface sediments collected in reservoir. Tetra-CNs consistently dominate in reservoir sediments, however, Penta-, Tetra- and Mono-CNs dominate in sediments collected at different sampling sites of the river investigated, suggesting that various sources contribute to PCNs collected from river. Indeed, diagnostic ratios indicate that mix-source contribute to PCNs measured in sediments collected from the reservoir and river in northern Taiwan.