Toluene Concentration Research Articles

Decorating {0 0 1} TiO2 nanosheets on hydrophobic NaY zeolite: An efficient deactivation-resistant photocatalyst for gaseous toluene removal

Photocatalysis is regarded as a promising in situ air purification technology for the removal of volatile organic compounds. However, the deactivation of photocatalysts remains a serious issue that needs to be addressed. Herein, we report a novel dual-functional photocatalyst (TiO2@HYZ) with spatially separated catalytic sites and adsorption sites, which has been obtained by combining hydrophilic {001} TiO2 nanosheets with hydrophobic NaY zeolite. TiO2@HYZ showed excellent photocatalytic activity for the degradation of gaseous toluene under UV irradiation in humid air. The optimized TiO2@HYZ-2 (containing 45.7 wt% TiO2) achieved 96.6% toluene removal and 87.4% mineralization within 120 min. The specific reaction rate constant of TiO2@HYZ-2, pristine TiO2 and P25 normalized by the unit amount of TiO2 during the photocatalytic degradation process were calculated to be 0.481, 0.230 and 0.250 min−1 g−1, respectively. Moreover, TiO2@HYZ-2 showed superior durability, maintaining stable performance over repeated toluene degradation processes, even at high toluene concentration, whereas pristine TiO2 incurred severe deactivation with increasing number of photocatalysis cycles. The significantly enhanced activity and anti-deactivation property was attributed to a synergistic effect between HYZ and TiO2 in the catalyst structure, which strengthened the adsorption of toluene on HYZ and facilitated effective separation of photoexcited charge carriers on TiO2, thus avoiding the deposition of degradation intermediates on the active sites and simultaneously improving mineralization. This work provided a new perspective for the design of efficient and deactivation-resistant photocatalysts for air pollution remediation.

Experimental and numerical study of flame stability in a rotary flow reversal reactor with ultra-lean toluene/air mixture

A rotary flow reversal reactor with a fixed packed bed and rotary intake is established to study the combustion stability with ultra-lean toluene/air mixture. The experimental results show that the stable temperature distribution in the packed bed is vertically graded and circumferentially uniform with bottom rotary intake. The three-dimensional numerical simulation using sliding grid technology on the combustion process is presented. The effects of intake toluene concentration, axial velocity and circumferential rotation speed on the combustion stability are analyzed numerically. High intake toluene concentration or feed axial velocity will decrease the propagation velocity of the flame front and raise the peak temperature and the maximum reaction rate to achieve a quasi-steady state finally. However, the intake rotation speed has little effect on the combustion process. The work will enrich the investigation of flame stability during the filtration combustion of ultra low-calorific value gas.

Air Pollutant Patterns and Human Health Risk following the East Palestine, Ohio, Train Derailment.

On February 3, 2023, a train carrying numerous hazardous chemicals derailed in East Palestine, OH, spurring temporary evacuation of residents and a controlled burn of some of the hazardous cargo. Residents reported health symptoms, including headaches and respiratory, skin, and eye irritation. Initial data from U.S. Environmental Protection Agency (EPA) stationary air monitors indicated levels of potential concern for air toxics based on hazard quotient calculations. To provide complementary data, we conducted mobile air quality sampling on February 20 and 21 using proton transfer reaction-mass spectrometry. Measurements were taken at 1 s intervals along routes designed to sample both close to and farther from the derailment. Mobile air monitoring indicated that average concentrations of benzene, toluene, xylenes, and vinyl chloride were below minimal risk levels for intermediate and chronic exposures, similar to EPA stationary monitoring data. Levels of acrolein were high relative to those of other volatile organic compounds, with spatial analyses showing levels in East Palestine up to 6 times higher than the local rural background. Nontargeted analyses identified levels of additional unique compounds above background levels, some displaying spatiotemporal patterns similar to that of acrolein and others exhibiting distinct hot spots. These initial findings warrant follow-up mobile air quality monitoring to characterize longitudinal exposure and risk levels.

Exposure assessment to BTEX in the air of nail salons in Tehran city, Iran

The nail salon industry has grown considerably, but there are serious concerns about the health risks associated with working in this field. Therefore, the purpose of this study was to investigate the exposure of nail technicians to BTEX. A cross-sectional study was conducted on 49 salons, and NIOSH Method 1501 was used to measure the concentration of BTEX in the breathing zone of technicians. The EPA method was used to assess health risks. Statistical analysis was conducted using SPSS software. The mean concentrations of toluene were (82.65 ± 198.84µg/m3)µg/m3, followed by benzene (10.58 ± 9.62µg/m3), p-xylenes (20.77 ± 37.79µg/m3), o-xylene (13.79 ± 25.70µg/m3), and ethylbenzene (29.35 ± 58.26µg/m3) , that lower than the permissible exposure limits suggested by NIOSH. Among the BTEX, toluene (82.65 ± 198.84µg/m3) has the most concentration in the nail salons. It was also discovered through multiple linear regression analysis that humidity had a significant effect on increasing the concentration of toluene (Beta = 0.50, P-value = 0.001) and ethylbenzene (Beta = 0.16, P = 0.049), while there was a considerable association between the number of services performed and benzene concentration (Beta = 0.34, P = 0.010).The average inhalation lifetime cancer risk for benzene (4.9 × 10 −5±4.5 × 10−5) was higher than the recommended value set by the US EPA. Although the concentrations of BTEX were lower than the maximum permissible limits, the results of the cancer risk assessment for benzene showed that working in nail salons with poor ventilation is hazardous. Therefore, exposure can be minimized by ensuring appropriate ventilation in the workplace and using safe products.

Interpretation of odor complaint records with BTEX pollutants and meteorological factors: Çorlu case study

Air pollution in urban areas increases as a result of emitted air from different sources within the mixing layer of troposphere. Odor pollution is amongst the primary reasons behind environmental nuisance and occurrence of citizen complaints. Frequent exposure to odorous compounds and/or odor nuisance are increasingly associated with air pollution problems. Besides, there is no universally accepted environmental odor management method reported so far. Level of air pollutants emission, distance of emission sources to residential areas, to-pography, geographical and meteorological conditions have influence on imposed level of air pollution and odor pollution in cities.
 
 This study is built on the citizen odor complaint data (based on frequency, intensity, duration, odor tone and location (namely the FIDOL factors) collected in Çorlu/Tekirdağ through the GIS integrated public participated platform, namely the Çorlu KODER mobile application. The annual odor complaint data was briefly introduced and given an evaluation with the mo-bile app users demographic information. The obtained data between August 28-November 2 of 2021, was subjected to interpretative evaluation and statistical analysis with BTEX (benzene, toluene, ethylene benzene and xylen) concentrations, inorganic air pollution concentrations and meteorological factors. In light of the obtained results, temperature, wind speed, relative humidity and toluene concentration were found to play a significant role on the number of citizen odor complaints. The EU reported limit value, lower rating threshold and upper rating threshold for BTEX pollutants have been exceeded several times.
 
 The average Toluene/benzene ratios obtained during the study show that; non-traffic sources contribute significantly to VOC emissions. Air pollutants transportation mechanism from neighbouring OIZ settlements become a prominent justification and support the hypothesis that residential areas of Corlu are under the effect of industrial air pollution and odor pollution con-stituents. There is low level of negative correlation between the benzene measured in Çorlu and WS (r=-0.63). Below 2.4 m/s, the average number of odor complaints (ANOC) tend to increase, while above this level odor complaints are diminished). The ANOC remained around 4 for[C] < 4 ug/m3 and reached to 18 for [C]BTEXtotal > 8 ug/m3. Above [C]Toluen=3 ug/m3 conditions, Daily ANOC increase from 7 to 19. Over [C]Toluen= 4 ug/m3 conditions, it reached up to 23. Increses in the number of daily ANOC by temperature is distinct over 21 C0 and reaches to 35. 
 
 The GIS integrated citizen complaint collection platforms are critical for real-time data collection of environmental complaints with high spatiotemporal accuracy. Citizen odor complaint surveys are useful monitoring tools and obtained data sets can be used to identify sensitive areas where and when specific actions should be taken and air pollutants measuement studies be performed.

Enhanced toluene gas-sensing properties of MEMS sensor based on Pt-loaded SnO2 nanoparticles

Rapid detection of low concentration toluene is highly desirable in environment monitoring, industrial processes, medical diagnosis, etc. In this study, we prepared Pt-loaded SnO2 monodispersed nanoparticles through hydrothermal method and assembled a sensor based on micro-electro-mechanical system (MEMS) to detect toluene. Compared with the pure SnO2, the 2.92 wt% Pt-loaded SnO2 sensor exhibits a 2.75 times higher gas sensitivity to toluene at about 330 °C. Meanwhile, the 2.92 wt% Pt-loaded SnO2 sensor also has a stable and good response to 100 ppb of toluene. Its theoretical detection limit is calculated as low as 12.6 ppb. Also, the sensor has a short response time of ∼10 s to different gas concentrations, as well as the excellent dynamic response—recovery characteristics, selectivity, and stability. The improved performance of Pt-loaded SnO2 sensor can be explained by the increase of oxygen vacancies and chemisorbed oxygen species. The electronic and chemical sensitization of Pt to SnO2-based sensor, together with small size and fast gas diffusion of the MEMS design ensured fast response and ultra-low toluene detection. This provides new ideas and decent prospect for developing miniaturized, low-power-consumption, and portable application of gas sensing devices.

Study on catalytic degradation of toluene by copper manganese composite oxide

AbstractHerein, Cu–Mn catalysts were used to study the catalytic oxidation system of toluene, revealing the optimal preparation conditions for catalytic oxidation of toluene and the effects of other factors on catalytic performance (oxygen concentration, toluene concentration, temperature, humidity, space velocity). The as‐synthesized Cu2Mn1Ox exhibited the best catalytic activity and stability. The BET, XRD, and O2‐TPD results indicated that the synthesized Cu2Mn1 catalyst can effectively form the Cu1.4Mn1.6O4 phase at the optimal calcination temperature (500–600°C) and accelerate the toluene degradation at 220°C. Although water vapor can promote the progress of catalytic reactions, excessive water vapor tends to form competitive adsorption at active sites, inhibiting the progress of catalytic reactions. In addition, oxygen concentration plays a key role in catalytic reactions. Based on the results, it was found that at lower oxygen concentrations or higher toluene concentrations, the catalyst was easy to react with toluene to generate Cu and MnO, resulting in catalyst deactivation.

Application of Co-Mn-Al sheet-like metal oxide catalysts in the liquid phase conversion of toluene to benzaldehyde

The main problems of liquid-phase oxidation of methylarenes to benzaldehydes are that the catalytic reaction rate is slow, benzaldehydes are easily over-oxidized to form benzoic acids, and a large amount of solvent is required. These problems make it difficult to realize the liquid phase catalytic oxidation of methylarenes to benzaldehydes in industrial production. Here, we report the catalytic oxidation of toluene to form benzaldehyde, by using N-hydroxyphthalimide (NHPI) as the radical catalyst, sheet-like Co-Mn-Al oxides (CMA-n) as the redox catalyst, and 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) as the solvent. CMA-n/NHPI was found to be highly active in catalyzing the oxidation of toluene to benzaldehyde. The use of HFIP as the solvent prevents the over-oxidation of benzaldehyde to benzoic acid. In addition, the reaction proceeded at a high concentration of toluene. The conversion rate of toluene reached 5826 μmol g−1 h−1, and the generation rate of benzaldehyde reached 4049 μmol g−1 h−1.

Features of C60 fullerene in the toluene-hexane solvent system

he behaviors of self-aggregation of C60 molecules in solution of C60/toluene/hexane were studied by the methods of refractometry, ultraviolet-visible spectroscopy, dynamic light scattering (DLS) and electron microscopy. It has been experimentally shown that with a slight increase in both the concentration of C60 fullerene and the volume fraction of toluene in a C60/toluene/hexane solution, a change in the refractive index of the medium and in the behavior of the optical spectrum is observed. An increase in the content of toluene in the solution manifests both a positive solvatochromic effect and a hyperchromic effect in the intense absorption band at 328.8 nm. At the same time, it was established by DLS that with an increase in the mole fraction of toluene in the C60/toluene/hexane system, the size of nanoclusters synthesized inside the solution decreases. After evaporation of hexane/toluene from fullerene solution droplets transferred to a heated substrate (up to 30°C), filamentary crystalline nanostructures based on C60 fullerene are formed on the substrate surface.

Pyrolysis of different types of waste cooking oil in the presence/absence HZSM-5 catalyst: Influence of feedstock characteristics on aromatic formation

In this study, aromatics were prepared by continuous microwave pyrolysis experiment in the presence and absence of HZSM-5 using different types of waste cooking oil (corn oil, rice oil, rapeseed oil, sunflower seed oil, soybean oil, blending oil, peanut oil, palm oil), and the effects of raw material characteristics on pyrolysis products were compared. The results showed that the fatty acid composition of waste cooking oil affects the composition of pyrolysis products. For example, linoleic acid promotes naphthene and inhibits olefin formation; oleic acid is easy to form C9 and C10 compounds; compared with oleic acid and linoleic acid, palmitic acid is not conducive to deoxidation. In addition, the deoxidation degree of waste cooking oil is related to the raw material H/Ceff, and the order from high to low is corn oil > rapeseed oil > sunflower seed oil > peanut oil > soybean oil. The yield of the oxygen-containing compounds is inversely proportional to it. With the use of HZSM-5 catalyst, the content of toluene and xylene in liquid products is significantly increases, especially the content of xylene. The catalytic effect of rice oil is the most significant, with xylene content increased by 19.2% compared with the non-catalytic pyrolysis. This provides a reference for the efficient treatment of waste oil and the production of aromatics in the future.

Emission Ratios and Diurnal Variability of Volatile Organic Compounds and Influence of Industrial Emissions in Two Texas Cities

Changing urban emission landscapes and increasing population make it imperative to understand the driving forces for air quality in growing urban areas. Recent field studies in an industrial area in Houston and a semiurban area in San Antonio reveal unique emission signatures for these two growing Texas cities. A comparison of benzene, toluene, xylenes, isoprene, and methyl ethyl ketone (MEK) was conducted for these two Texas locations and previous studies in other megacities. It was found that San Antonio had similar emission ratios as these megacities for benzene, toluene, and xylenes (1.10, 4.57, and 3.60 pptv ppbv−1 of CO, respectively), likely indicating a similar traffic emission source. Isoprene and MEK were of biogenic origin in San Antonio. However, analysis of emission ratios, diurnal trends, and comparison with emission inventories indicated that benzene, toluene, and MEK were likely associated with fugitive and stack emissions in the industrial corridor in Houston. Isoprene in Houston appeared to have mixed fugitive and biogenic sources in Houston, based on diurnal trends and emission ratio. The peak nighttime concentrations for benzene, toluene, xylene, isoprene, and MEK observed during the campaign were 66, 533, 21, 138, and 731 ppbv, respectively, in the Houston site. The emission ratio for xylenes (3.37 pptv ppbv−1 of CO) for the Houston site was similar to Paris, London, and Mexico City, despite emission inventories indicating high fugitive and stack emissions. The conditional probability function (CPF) analysis closely matched the direction of the industrial sources with the highest recorded emission levels as listed in the emission inventory for the Houston site. The estimated ozone production efficiency (OPE) for the industrial area in Houston indicated volatile organic compound (VOC)–limited conditions in the morning, which transitioned to nitrogen oxide (NOx)–limited conditions in the afternoon. Texas cities have complex emission scenarios, and future efforts to mitigate ozone and particulate matter may have to consider a variety of emission reduction strategies.

Gas-particle two-phase adsorption of toluene and ultrafine particles on activated carbon studied by molecular simulation

Adsorption is regarded as the most reliable technology for gaseous pollutant removal. Activated carbon is a widely used adsorbent due to its good adsorption capacity and low price. However, substantial ultrafine particles (UFPs) in the air cannot be effectively removed even if a high-efficiency particulate air filter is located before the adsorption stage. The adhesion of UFPs to the porous surface of activated carbon affects the removal of gaseous pollutants and shortens its service life. So, we adopted molecular simulation to explore the gas-particle two-phase adsorption and analyze the effects of the properties of UFPs such as concentration, shape, size and chemical composition on the toluene adsorption. The parameters of equilibrium capacity, diffusion coefficient, adsorption site, radial distribution function, adsorption heat and energy distribution were used to evaluate the gas adsorption performance. The results showed that the equilibrium capacity of toluene was decreased by 16.51 % compared to that of only toluene adsorption at the toluene concentration of 1 ppb and UFPs concentration of 1.81 × 10−5/cm3. Compared with cubic and cylindrical particles, the particles in spheres were more likely to hinder the pore channels from reducing gas capacity. Larger UFPs in the selected particle size range (1–3 nm) had a greater impact. Carbon black UFPs themselves could adsorb toluene, so the amount of toluene adsorbed was not significantly decreased.

Multicomponent Gas Detection Method via Dynamic Temperature Modulation Measurements Based on Semiconductor Gas Sensor

Leakage of organic gas in industrial environment can easily cause fire and explosion accidents. Rapid detection of gases type and concentration is the premise for emergency treatment of these situations. Typically, the single semiconductor sensor cannot detect multi-component gas. Here, a new multi-component gas detection method was proposed based on the temperature-response relationship of sensor. This method has low power consumption, low cost and long-term monitoring, which can guide the future exploration of deployable sensors. Firstly, the parameters were optimized according to cosine distance to reflect the maximum difference of temperature-response relationship. Then coordinate system transformation was carried out to further magnify the difference between gases. Finally, the multi-component gas was recognized by using rational taylor function fitting. As a proof-of-concept, we measured the type and concentration of toluene and butanone multi-component gas with mean error of 6.34&#x0025; and 4.32&#x0025; respectively. We analyzed the gas-sensing response mechanism, the theoretical support of the optimized parameters and the causes of local errors. As a universal method, binary component gas detection was <b>explored</b> containing toluene, butanone, acetic anhydride, acetone and diethyl ether.

Volatile Organic Compounds (VOCs) and Interleukin-23 Levels in Lung Cancer: A Future Biomarker

Introduction: Lung cancer (LC) is the world's second leading cause of death due to malignancy. In Indonesia, LC is one of the top three malignancies. Volatile organic compounds (VOCs) from the respiratory reflect changes in metabolism caused by disease and may be a biomarker of LC. Interleukin-23 (IL-23) has been known as a pro-inflammatory cytokine in the development and progression of cancer. This study aimed to identify levels of IL-23 and VOCs in LC patients. Methods: This study involved 40 LC patients and 42 controls. VOCs were taken by the subject exhaling their third deep breath into the sample bag, which was immediately analyzed using an E-nose-based device. As for the IL-23, the cytokine was taken from the blood serum and then analyzed using the ELISA method. Kolmogorov-Smirnov and Shapiro-Wilk tests were performed to test data normality. Mann-Whitney and Kruskal Wallis tests were conducted for variables. Spearman correlation and heat map were used to find the correlation between the observed gases and IL-23. Results: The concentration of ozone (p = 0.000), ethanol (p = 0.000), formaldehyde (p = 0.000), toluene (p = 0.000), acetone (p = 0.000), ammonia (p = 0.000), ammonium (p = 0.001), nitrogen (p = 0.001) and methane (p = 0.000) in LC group differed with controls. The same outcome was also observed in comparing LC patients and control groups of IL-23 (p = 0.000). Spearman correlation analysis revealed a positive correlation between serum IL-23 with formaldehyde (p = 0.029), toluene (p = 0.014), and ammonia (p = 0.028) and a negative correlation with nitrogen (p = 0.011). Compared to the control group, all types of LC were observed to have higher levels of IL-23. A weak positive correlation was found in formaldehyde (Cv = 0.23), toluene (Cv = 0.23), and ammonia (Cv = 0.13). A weak negative correlation was obtained in acetone (Cv = -0.12), ammonium (Cv = -0.11), and nitrogen dioxide (Cv = 0.23). Conclusion: Weak linear correlations were obtained between the cytokine and formaldehyde, toluene, ammonia, ammonium, and nitrogen dioxide. A higher IL-23 concentration was observed in the LC group than in the control group. The volatile concentration was significantly different between LC and control groups.

WRF-Chem quantification of transport events and emissions sensitivity in Korea during KORUS-AQ

To quantify the relative roles of long-range transport (LRT) versus locally emitted aerosol and ozone precursors during polluted periods in Korea, high-resolution (4 km) Weather Research and Forecasting with Chemistry model simulations were performed. The model was evaluated using surface and airborne observations collected during the KORea and United States Air Quality campaign. Ozone above 40 ppb had mean bias of −5.9 ppb. PM2.5 was biased high (8.2 µg/m3), with a relative bias of 30% given the mean observed value of 26.8 µg/m3. The absolute amounts and shifts between phases for all PM2.5 species except nitrate reasonably match observations across all 4 phases. Notable limitations include an underestimation of nighttime planetary boundary layer height. Transport versus domestic emissions influence was studied by model runs with perturbed emissions and by comparing east-west fluxes over the Yellow Sea to Korean emissions and other normalization metrics. Domestic anthropogenic emission contributions to surface air quality were quantified by location across Korea, segregated by synoptic meteorological phase. The largest contributions from Korean emissions were found under high-pressure stagnant conditions and the smallest for conditions with strong westerly winds. For example, at Seoul, domestic contributions of PM2.5 averaged 49% and 29% in the aforementioned meteorological phases, respectively. Surface concentrations of NOx and toluene in Seoul were over 85% due to domestic emissions. CO and black carbon had both local and remote contributions. Nitrate and ammonium contributions varied greatly by phases in Seoul, with 7%–51% nitrate and 42%–70% of ammonium from remote sources. Variation in direction (west-to-east vs. east-to-west) and magnitude of fluxes support the model sensitivity results. Analysis using fluxes facilitates the quantification of source contributions for secondary species and, in many cases, can be done using a single model run or reanalysis result. The analysis presented shows the importance of using models with high spatial resolution to capture pollutant transport and mixing around Korea. However, there remain uncertainties in secondary aerosol production mechanisms and indications that local production at times could be higher than those modeled in this analysis. Therefore, the results presented here should be viewed as an upper limit on the importance of LRT.

Assessment of health risk and burden of disease induced by exposure to benzene, toluene, ethylbenzene, and xylene in the outdoor air in Tehran, Iran.

The health risk and burden of disease induced by exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) in the outdoor air in Tehran, 2019 were assessed based on the data of five fixed stations with weekly BTEX measurements. The non-carcinogenic risk, carcinogenic risk, and disease burden from exposure to BTEX compounds were determined by hazard index (HI), incremental lifetime cancer risk (ILCR), and disability-adjusted life year (DALY), respectively. The average annual concentrations of benzene, toluene, ethylbenzene, and xylene in the outdoor air in Tehran were 6.59, 21.62, 4.68, and 20.88 μg/m3, respectively. The lowest seasonal BTEX concentrations were observed in spring and the highest ones occurred in summer. The HI values of BTEX in the outdoor air in Tehran by district ranged from 0.34 to 0.58 (less than one). The average ILCR values of benzene and ethylbenzene were 5.37 × 10-5 and 1.23 × 10-5, respectively (in the range of probable increased cancer risk). The DALYs, death, DALY rate (per 100,000 people) and death rate (per 100,000 people) induced by BTEX exposure in the outdoor air in Tehran were determined to be 180.21, 3.51, 2.07, and 0.04, respectively. The five highest attributable DALY rates in Tehran by district were observed in the districts 10 (2.60), 11 (2.43), 17 (2.41), 20 (2.32), and 9 (2.32), respectively. The corrective measures such as controlling road traffic and improving the quality of vehicles and gasoline in Tehran could reduce the burden of disease from BTEX along with the health effects of other outdoor air pollutants.

Identify Primary Air Pollution Sources of BTEX by Using Positive Matrix Factorization (PMF): A Case Study of Ho Chi Minh City, Vietnam.

Ho Chi Minh City (HCMC) is one of the main socioeconomic and financial centers of Vietnam. The city also faces serious air pollution. However, the city polluted with benzene, toluene, ethylbenzene, and xylene (BTEX) has rarely been studied. We used positive matrix factorization (PMF) to analyze BTEX concentrations measured at two sampling locations to identify the main sources of BTEX in HCMC. The locations represented residential area (i.e., To Hien Thanh) and industrial area (i.e., Tan Binh Industrial Park). At the To Hien Thanh location, the average concentrations of benzene, ethylbenzene, toluene, and xylene were 6.9, 14.4, 4.9, and 12.7µg/m3, respectively. At the Tan Binh location, the average concentrations of benzene, ethylbenzene, toluene, and xylene were 9.8, 22.6, 2.4, and 9.2µg/m3, respectively. The results showed that PMF was a reliable model for source apportionment in HCMC. Traffic activities were the main sources of BTEX. Besides, industrial activities also contributed to BTEX emissions, especially the location near the industrial park. The majority of BTEXs at the To Hien Thanh sampling site come from traffic sources accounting for 56.2%. Activities from traffic and photochemical reactions (42.7%) and industrial sources (40.5%) were the main sources affecting BTEX emissions at the sampling site of Tan Binh Industrial Park. This study can be used as a reference for mitigation solutions to reduce the BTEX emission in HCMC.

Decreasing Asphaltene Precipitation and Deposition during Immiscible Gas Injection Via the Introduction of a CO2-Soluble Asphaltene Inhibitor

Summary In this study, the ability of dilute concentrations of toluene to act as a CO2-soluble asphaltene stabilization agent capable of inhibiting asphaltene precipitation during immiscible CO2 injection was assessed. Phase behavior results indicated that 1,000 to 20,000 ppm toluene could readily dissolve in CO2 at cloudpoint pressures that are well below the formation pressure and typical CO2 minimum miscibility pressure (MMP) values during gas-based enhanced oil recovery (EOR). Single-phase solutions of the modified gas (CO2/toluene) were then combined with asphaltenic oils in oil swelling phase behavior tests to demonstrate that the presence of toluene increased the amount of CO2 that dissolved into reservoir crude oil at a specified temperature and pressure. However, asphaltene precipitation diminished, apparently because the effect of the increased asphaltene solvent strength of toluene was more significant than the increased amount of CO2 (an asphaltene antisolvent) that entered the oil-rich phase. During the injection of CO2/toluene solution into cores initially saturated with crude oil and brine, compared to the injection of pure CO2, asphaltene deposition declined during the injection of CO2/toluene mixtures for asphaltenic volatile and intermediate oils from 3.7 wt% to 0.7 wt% and 5.9 wt% to 1.7 wt%, respectively. Based on the asphaltene particle-size analysis, the CO2/toluene mixtures can stabilize oil particles and simultaneously reduce asphaltene aggregation more effectively than pure CO2.

Regulating side chain of flexible polyacrylate resins for efficient removal of trace dissolved organics with moderate polarity

Efficient removal of trace amounts of dissolved organics with moderate polarity (DOMP) in water via adsorption method is a challenge. Most typical adsorption materials such as activated carbon exhibits poor selectivity and few polymers can remove DOMP in water. Herein, four polyacrylate resin (PAR)-based materials with different side chain are successfully fabricated, which can selectively adsorb pure organics with moderate polarity (dielectric constant ranging from 2.21 to 21). Interestingly, PARs can also selectively remove low concentration of toluene (5 ppm) and chloroform (1 ppm) in water with maximum removal efficiencies of 98.16% and 95.65%, respectively. Molecular dynamic (MD) simulations reveals that the driving force and selectivity of the adsorption behaviors can be attributed to the van der Waals interactions between the side chain of PARs and organics. Our study provides a designing strategy and novel material for efficient removal of organic pollutants with trace amounts in water.

Effect of nitrogen source and spray conditions on the integral biotrickling filter operation for hydrophobic volatile organic compounds

A nutrient solution containing major and trace elements plays a crucial role in biotrickling filter (BTF) operation in practical applications. This study conducted a series of experiments on the BTF packed with integral filters using two types of nitrogen sources under different spray conditions. The rapid start-up was observed in the BTF feeding with ammonium tartrate-N (AT-N) nutrient solution. Heterotrophic nitrification and denitrification were observed by monitoring the concentration of ammonia-N, nitrite-N, nitrate-N, PO43− and SO42− in the nutrient solution. The BTF performance under two different types of the nutrient solutions were detected up to ∼90% at the inlet toluene concentration of 300–700 mg∙m−3. The BTF packed with integral filters exhibited the stable performance with the change of nitrogen source and could be steadily operated at a wide pH range of 5.5–8.5. To illustrate the effect of the two types of nitrogen sources on the biofilm, metagenomic sequencing was used to assess the microbial diversity and functional genes of biofilm on the integral filters. The results showed that the application of AT-N nutrient solution increased the functional genes of denitrification in the microorganisms on the filters. Furthermore, the more stable performance of BTF was achieved by using the AT-N nutrient solutions, which might be beneficial to the long-term operation of BTF packed with honeycomb integral packing.