Amir Shojaei; Hossein Ghafourian; Linda Yadegarian; Kamran Lari; Mohammadtaghi Sadatipour
Abstract
Abstract Background and Aim :The release of volatile organic compounds from stationary and mobile sources increases the concentration of these compounds in the environment. These compounds are potentially hazardous to the environment and human health. The selection of management and engineering systems ...
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Abstract Background and Aim :The release of volatile organic compounds from stationary and mobile sources increases the concentration of these compounds in the environment. These compounds are potentially hazardous to the environment and human health. The selection of management and engineering systems has become essential for controlling the release of these pollutants. The aim of this study was to use an advanced catalytic ozonation process to reduce the concentration of these pollutants in industrial emissions. Materials and Methods:In this experimental study, the ozonation process in the presence of a catalyst bed containing ZnO nanocomposites coated on zeolite was used to treat the air contaminated with BTEX compounds as indicators of volatile organic compounds on a laboratory scale. In this study, the synthesis of nanocomposites was done using the chemical co-deposition method. SEM, XRD, BET, and FT-IR analyses were performed to investigate the structural properties of the nanocomposites. The initial concentrations of BTEX (50-200 ppm), the flow of the polluted air (5-20 l/h), humidity (0-75%), and ozone dose (0.25-1 g/h) were studied. The concentration of the BTEX compounds was measured by a Gas Chromatography (GC) device according to the NIOSH Guideline 1501. Results:The results of SEM, XRD, BET, and FT-IR indicated the proper synthesis of nanocomposites. Based on the laboratory results, the optimal process conditions were the initial concentration of pollutants equal to 50 ppm, the inlet flow rate of polluted air equal to 5 l/h, relative humidity of 25-35%, and the inlet concentration of ozone equal to 1 g/h. Under these conditions, the removal efficiencies of benzene, toluene, ethylbenzene, and xylene were 98, 96, 92, and 91%, respectively. Simple ozonation and adsorption processes had lower efficiencies than catalytic ozonation and the synergistic effect of the process was evident. Conclusion:Based on the obtained results, the process has the ability to reduce the concentration of BTEX compounds to the specified standards. This process can be used to treat polluted air in BTEX emitting industries that threaten human health and the environment. Article type:Research article Keywords: Volatile Organic Compounds; BTEX; Nanocomposite; Zinc Oxide; Ozone; Polluted Air
faezeh borhani; Mohsen Mirmohammadi; Alireza Aslemand
Abstract
Back ground: Urbanization and development has always been led to air pollution. Volatile organic compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX) are known as one of the most important groups of air pollutants. The present study aims to measureand investigate the outdoor concentrations ...
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Back ground: Urbanization and development has always been led to air pollution. Volatile organic compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX) are known as one of the most important groups of air pollutants. The present study aims to measureand investigate the outdoor concentrations of BTEX in Tehran, Iran. Methods and Materials: The National Institute for Occupational Safety and Health (NIOSH)'s methods were applied to measure the concentrations of BTEX in winter and spring of 2015 at 46 stations as well as in July 2003 at 19 stations. Sample preparation and extraction were accomplished by CS2 solvent. Sample and data analysis were performed by Gas Chromathography (GC) and SPSS-16 software respectively. Results: In 2003, The BTEX pollutants were more observed in the eastern, central and southern zones of Tehran, respectively. The average concentrations of BTEX were 238, 130, 69 and 118 ppb, respectively. The benzene to toluene (B/T) ratios were between 0.8 to 3.2, which indicated the poor quality of gasoline. In 2015, the BTEX concentrations in District 19 (south of Tehran) were higher than eastern and central regions, which located in traffic zones with extensive development in public transportations. Conclusions: Improvement of gasoline quality, renewal of private cars and development of subway and public transportation till 2015 can be considered as the most important factors in decreasingBTEX concentrations to allowable amounts. During this year, thehe average concentrations of BTEX were 5.3 ppb, 9.2 ppb, 1.5 ppb and 2.6 ppb, respectively. The B/T ratio was fluctuated between 0.39 to 0.76, which depicted the remarkable role of vehicle traffic in BTEX pollution.
Ismael Javadi; Yosef Mohammadian; Behzad heybati; Sima Elyasi
Abstract
Background and Aims: ٌWith increasing the number of motor vehicles that causes increasing the fuel production and sale, the ambient air quality has been worse. BTEX is one group of the important pollutants that release from gasoline and its burning. The aim of this study is evaluation of BTEX level ...
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Background and Aims: ٌWith increasing the number of motor vehicles that causes increasing the fuel production and sale, the ambient air quality has been worse. BTEX is one group of the important pollutants that release from gasoline and its burning. The aim of this study is evaluation of BTEX level in refueling station ambient air. Methods: In this cross-sectional study, the air samples were taken from 24 workers’ breathing zones in 12 gasoline and CNG refueling stations. Samples were analyzed according to NIOSH1501 method and using GC-FID technique. SPSS-v.16 is used to analyze data with t-test and Linear Regression (p<0.05). Result: The mean concentration of benzene, toluene, ethyl-benzene and xylene in gasoline stations was 1787±327, 914±141, 973.4±183 µg/m3 and 476.1±123 respectively, and about CNG stations, there were 1142/9±863, 507.6±458, 694.9±514 and 296±245.6 µg/m3, in that order. The CNG station’s workers, who exposed to benzene, have cancer risk about 15.8×10-6 and the highest HQ index was related to xylene (i.e. 8.656). The cancer risk of gasoline station workers and HQ index were 21.6×10-6 and 16.19 respectively. Conclusion: Gasoline stations had the highest concentration of benzene that exceeded the OEL-TWA. Cancer and non-cancer risk is in high levels that require decisions to control the condition. Improvement of fuel quality, implementation of vapor recovery systems, smarting the refuel instruments, utilization of plants for purification of BTEX and using of personal protective equipment are our recommendation for improvement of condition.