Papers by Keyword: BTEX

Abstract: Carbon (C)-doped TiO₂ nanospheres were produced using a solvothermal method, and then characterised with transmission electron microscopy, powder X-ray diffraction pattern and X-ray photoelectron spectroscopy. The C was doped into the TiO₂ nanosphere as planned, and the photocatalytic oxidations were studied in environmental chambers under simulative conditions. C-doped TiO₂ nanospheres' photocatalytic performance was evaluated by removing benzene, toluene, ethylbenzene, xylenes (BTEX) of paint thinners via the illumination of visible light. A degradation ratio of 93.4% in 90 min exhibited high photocatalytic activity.

Abstract: S-doped TiO₂ nanoparticles were fabricated by hydrothermal process and post-calcination, and their morphology, crystalline phase and chemical composition were characterized with transmission electron microscopy, powder X-ray diffraction and selected area electron diffraction. The results showed that S was successfully doped into the TiO₂. We investigated the photocatalytic reactions in a simulated environment in tandem with thermal desorption-gas chromatography-mass spectrometry determinations. The catalytic activity of S-doped TiO₂ was evaluated by monitoring the photodegradation of BTEX from wood-based panels, and 95% degradation rate in 75 min demonstrated efficient visible-light catalytic performance.

Abstract: Dense membranes made of polybenzodioxane (PIM-1) were developed for pervaporation of toluene/TEG mixtures. The effect of experiment time on membrane characteristics such as flux and separation factor was investigated. The neat PIM-1 membranes showed high toluene flux of 2.45 kg/m²∙h, but low separation factor of 4. The cross-linking of PIM-1 using AlCl₃ leads to an increase in the separation factor up to 20, with some compromise of toluene flux down to 0.76 kg/m²∙h.

Abstract: The volatile organic compounds (VOCs) contribute to serious air pollution problems in Viet Nam. Many studies have investigated in air quality monitoring and treatment, in order to determine the average concentrations of Benzene, Toluene, Ethylbenzene and Xylene (BTEX). Carbon nanotubes (CNTs) have been widely used as adsorbent in environmental treatment, especially for VOCs. This paper aims to determine the adsorption capacity of multiwalled carbon nanotubes for removal of BTEX from air samples. In preliminary study, the effects of various parameters during adsorption experiments were monitored such as flow rate, temperature and BTEX concentrations in air samples. The equipment for BTEX removal was developed by our research team consisting of filter columns, air sample bags, adsorption cartridge. The air samples containing BTEX were conducted directly through a cartridge packed with adsorbent. The adsorption experiments were carried out under various operating conditions such as temperature (30 - 40°C), gas concentration (0,57 - 4,77 mg/L) and the gas flow rate (10 - 90 mL/min). In addition, isotherm studies of CNTs for BTEX removal were achieved by using Langmuir and Freundlich models. The results showed that the experimental parameters were optimized at a flow rate of 30 mL/min and an ambient temperature at 30°C. The adsorption capacity of CNTs increased proportionally with BTEX concentrations. The specific affinity of CNTs for BTEX from air samples was in order of X > E > T > B. The experimental isotherm data were well-fit with the Langmuir model for Benzene and Xylene removal, and the Freundlich model for Toluene and Ethylbenzene adsorption. The CNTs presented highly potential application for BTEX adsorption thanks to their microporous structure and high surface area.

Abstract: Vehicles are the dominant source of many air pollutant emissions in urban areas. The effects caused by vehicle emissions have been receiving increasing attention, and recent epidemiological studies show elevated risks of cardiovascular morbidity, cancer, allergic diseases for drivers, commuters and individuals living near roadways. During the experimental research conducted in this paper, emission characteristics of Otto 1.1 EFI engine were investigated in varying operating modes in order to adequately simulate the movement of the Fiat Punto Classic (FPC) passenger car in city driving conditions in line with the New European Driving Cycle (NEDC). The NEDC is a stylized cycle, with periods of constant acceleration, deceleration and constant speed, and it is supposed to represent the typical usage of a passenger car in Europe. The analysis of exhaust gas samples was conducted by using the gas chromatography technique in combination with the photoionization detector (GC/PID). The results of emission tests indicate high concentration levels of toluene in the exhaust gas mixtures, ranging from 7.07 to 116.87 ppm. The total mass of the emitted toluene after 100 km of driving in accordance with the NEDC was 7.7647 g.

Abstract: The determination of volatile organic compounds (VOCs) at selected pump stations in Skudai, Johor Bahru was investigated. About 27 chemicals substances in petrol and 24 chemicals substances in diesel with different concentration have been identified in each pump station. Benzene, toluene, ethylbenzene and xylene (BTEX) and MTBE have been chosen as VOCs of interests because of their toxicity properties that can gives hazardous to human health. The exposures of benzene at all three pump stations during refuelling the liquid fuel have potential to cause cancer riskwhile, ethylbenzene stated as acceptable risk to the people health.As for non-carcinogenic substances, the exposure of toluene, xylene and MTBE were recorded as acceptable risk to the people health at all the studied pump stations. Besides, there is a great correlation between physical environment factors; temperature, relative humidity and wind speed typically with total volatile organic compounds that evaporate into the ambient air during refuelling activities.

Abstract: Adsorptive biological reactive barrier comprising medium sand-bentonite-microorganism for removing simulated groundwater BTEX (benzene, toluene, ethyl benzene, xylene) of different concentrations has been investigated with the variance of filling media ratio, and the dependence of BTEX removal efficiency in groundwater on electron acceptor was also studied through adding nitrate. The results show that the optimum volume ratio of bentonite-medium sand is 20:80, with a permeable reactive barrier permeability coefficient of 2.01 × 10^-5 m/s and effective porosity of 16.71%. The addition of nitrate to biological reactive barrier stabilized BTEX removals under different concentrations, comparatively, while the control group without nitrate exhibited volatile BTEX removal efficiency. Under conditions of influent concentrations of 6, 8 and 10 mg/L, the BETX removal rates of biological reactive barrier with/without the addition of nitrate and the control group are about 94%/91%, 96%/90%, and 97%/87%, respectively. The adsorptive biological reactive barrier shows significant performance on BTEX removal, especially with the aid of nitrate additive.

Abstract: The content of characteristic pollutants including methyl tert-butyl ether (MTBE) and benzene, toluene, ethyl benzene, p-xylene, m-xylene and o-xylene (BTEX) were determined by head-space-GC. A HP-FFAP capillary column was used in this method. In the mass concentration range of 14.8μg·L^-1~1760μg·L^-1, there were good linearity relationships between the GC peak areas and the mass concentrations of components with correlation coefficient above 0.999.The detection limits were in the rage of 2.0μg·L^-1~2.3μg·L^-1. Tests for recoveries and precision were made by standard addition method, values of recoveries and RSDs (n=6) found were in the range of 95%~105% and 0.8%~5.5%.

Abstract: An indigenous Pseudomonas sp., isolated from the heavily petroleum-contaminated soil and identified as Pseudomonas plecoglossicida, was evaluated for its aerobic cometabolic removal of mixture of two representative chlorinated aliphatic hydrocarbons (CAHs), cis-1,2-dichloroethylene (cis-DCE) and trichloroethylene (TCE), with BTEX/toluene provided as substrate in a laboratory-scale soil slurry. The aerobic simultaneous bioremoval of the cis-DCE/TCE/BTEX mixture was studied under different conditions. Results showed that the increased BTEX concentration from 400 to 600 mg/kg prolonged the bioremoval of BTEX. The cometabolism of cis-DCE and TCE was significantly greater when toluene was provided as growth substrate compared to the BTEX mixture as substrates. Additionally, the bioremoval of toluene in the treatment with toluene as sole growth substrate was higher compared to the treatment with BTEX mixture as substrate. Results would enhance the applicability of bioremediation technology to the mixed wastes-contaminated sites.

Abstract: This study is aimed at examining environmental impacts of exhaust emissions imposed by various alcohol blending fuels. The tested fuels are 0%, 5%, 10%, 15% and 20% blending of methanol, ethanol or butanol alone. Rotation speeds of engine tests were controlled at 1500, 2500 and 3500 rpm to simulate slow, normal and fast speeds of vehicle driving. Gaseous emissions from engine exhaust were collected to determine the concentrations of CO, NO_x, HC, BTEX, formaldehyde and acetaldehyde. Most alcohol blending fuels were found able to lower regulated emission of CO, NO_x and HC as well as toxic constituents of BTEX more or less. Adversely, alcohol combustion in the engine could result in the formation of formaldehyde and acetaldehyde. Environmental impact on the release of formaldehyde should be aware and carefully controlled with the use of various alcohol blending fuels.