• Journal of the Korean Chemical Society
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• v.22 no.6
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• pp.380-385
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• 1978

Adsorption isotherms of o-xylene on Spheron 6, a graphitized carbon black, are obtained at various temperatures using a quartz beam microbalance. BET plots are made to estimate the molecular area of o-xylene from these isotherms. On Spheron 6, the molecular area of o-xylene (m.p $-25^{\circ}C$) remains constant until the temperature is increased up to $-15^{\circ}C$, but increases abruptly between $-15^{\circ}C$ and $-14^{\circ}C$, and then again remains constant thereafter. These results are interpreted as implying that the adsorbed o-xylene molecules are flatly localized on Spheron 6 with compact packing below $-15^{\circ}C$ while they gain a rotational degree of freedom around the benzene ring at the higher temperature.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.6
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• pp.463-474
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• 2001

In this study, the concentrations of major anthropogenic volatile organic compounds(VOCs) which include benzene, toluene, m, p-xylene, o-xylene, and ethylbenzene were measured at the Nan-ji-do landfill site during the spring and fall season of 2000. the temporal distribution characteristics of these VOCs were investigated over varying time scale. According to our study, the mean concentration of those species were computed to be 1.65$\pm$2.68(benzene), 9.62$\pm$9.32(toluene), 1.84$\pm$2.90(m, p-xylene), 0.83$\pm$1.43(o-xylene), and 1.17$\pm$1.21 ppb(ethylbenzene). The VOCs levels in the study area are not distinctively higher than the level typically found in urban area that can be subject to the influence of various anthropogenic source processes. Inspection of their temporal trends exhibited various patterns for the diurnal(and seasonal) cycle. Although each species showed distinctive patterns in temporal distribution trends, we were able to find the strong correlations among most concurrently measured VOCs except for benzene.

• Journal of Environmental Science International
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• v.18 no.5
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• pp.479-487
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• 2009

Because of the building is made airtight, Indoor Air Quality(IAQ) is go from bad to worse. There are many source of indoor pollution in any home. These include irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. Such immediate effects are usually short-term and treatable. In this study was measured and analyzed VOCs exposure levels and characteristic of Indoor air pollutant from new apartments in Korea. VOCs were measured indoor pre-residential and residential in new apartment and analyzed GC/MS. The concentration levels of indoor respirable TVOC were found to be higher than those of outdoor TVOC for new apartments. Before occupation, the average indoor and outdoor concentrations were 1498.61 $ug/m^3$ and 468.38 $ug/m^3$, respectively. After being occupied, the average indoor and outdoor concentration were 847.04 $ug/m^3$ and 102.84, respectively. The concentrations of TVOC in new apartments before occupation were shown in the order of Toluene(328.12 $ug/m^3$) > m,p-Xylene(163.67 $ug/m^3$) > Ethy1benzene(80.70 $ug/m^3$>o-XYlene (67.04$ug/m^3$). In addition, the TVOCs concentrations after occupation were also found in the order of Toluene (272.28 $ug/m^3$) > m.p-Xylene(121.79 $ug/m^3$) > Ethylbenzene(53.92 $ug/m^3$)>O-Xylene(24.94 $ug/m^3$). As a result, the concentrations of VOCs in new apartment houses were shown to be affected by indoor environment according activity patterns. So new apartments need to be controled in indoor air quality so that the residents can have more comfortable and healthier living environment.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.80-86
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• 2009

In this study, binderless zeolite BaX granule, an effective adsorbent for the separation of p-xylene was made. This adsorbent which has a sufficient strength, high specific surface area and selectivity to p-xylene was prepared by various steps, such as granulation process, calcination, binderless treatment, ion-exchange, and activation. In the granulation, the concentration of colloidal silica solution was controlled in order to confirm the effect of $SiO_2$ contents after binderless treatment. As a result, we confirmed that the compressive strength of granule after binderless treatment was increasing with increasing proportion of $SiO_2$ in the granule. And then Na-ion in granule was exchanged with Ba-ion by successive batch ion-exchange process. And then prepared adsorbents were tested for p-xylene separation by batch adsorption at $90^{\circ}C$. As a results of batch adsortion test, we confirmed that prepared adsorbents have a high selectivity to p-xylene. Also, it could be conformed that the prepared binderless zeolite BaX has a sufficient compressive strength (0.450 kgf), high specific surface area $(647.57m^2/g)$, high crystallinity (98.5% compared with zeolite NaX powder), and selectivity to p-xylene.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.335-338
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• 2000

To separate BTX degrading microorganisms, four kinds of activated sludges were obtained from waste water treatment plants and VOC generating plants, and adjusted 500 mg/L of BTX for three months. Y consortia degraded benzene and toluene in either individual or mixed compounds fast whereas A consortia degraded p-, m-, o-xylene fast.

• Journal of Environmental Science International
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• v.14 no.6
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• pp.543-553
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• 2005

In recent days, photochemical smog due to the rapid industry development and vehicle increasement has become a critical pollutant in the metropolitan area and the number of ozone alarm signal has increased every year. This research was performed to evaluate VOCs emission source characteristics and concentration of VOCs in Daegu. The site average concentration was observed in the following order: industrial area > commercial area > residential area. Most of the VOCs species except toluene showed variations with higher concentration during nighttime, and lower concentration during the daytime. The major VOCs of stationary emission source were BTEX(benzene, toluene, ethylbenzene. xylene) and methylene chloride, trichloroethene and styrene. Also, those of automobile exhaust were toluene and benzene. Also, the major VOCs concentration emited by the vehicle fuel was observed in the following order: gasoline > light oil > liquefied petroleum gas (L.P.G). Correlation coefficients values were estimated between major VOCs such as toluene, ethylbenzene, m,p-xylene, o-xylene. Results showed that correlation coefficient values were significant magnitude above 0.76. Also, there showed highly significant correlations among ethyl benzene, m,p-xylene, and o-xylene concentration(Pearson correlation coefficients, r=0.868-0.982). Calculated correlation coefficients among commercial area,industrial area and residential area were 0.934-0.981, they showed high correlation. There showed highly correlation between stationary emission source and industrial area, compared with commercial area and residential area. Also, calculated correlation coefficients among commercial area, industrial area, residential area and automobile exhaust were 0.732, 0.725, 0.777, respectively.

• Journal of Environmental Science International
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• v.12 no.4
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• pp.487-496
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• 2003

The purpose of this study was to develop the preliminary source fingerprints of volatile organic compounds (VOC). The source categories studied were vehicles, gasoline vapor, gasoline storage tank, coating, dry cleaning and road covering. The source samples were collected using 6L electro-polished stainless steel canisters for about 20 seconds. From this study, the main component emitted from VOC sources in Korea was toluene. The toluene proportion for road covering, vehicles, coating and gasoline vapor were 35, 18, 16 and 5%, respec- tively. The C$_2$-C$\sub$5/ alkane and alkene compounds were mainly emitted from vehicles, gasoline vapor and gasoline storage tank. The main compounds of coating were m/p-xylene(34%), toluene(16%), 1,2,4-TMB(10%) and o-xylene(9%), which are aromatic hydrocarbons. In the case of dry cleaning, nonane(41%), 1,2,4-TMB (22%) and 1,3,5-TMB(13%) were mainly emitted.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.5
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• pp.491-502
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• 2003

In the present work, the distribution characteristics of ambient volatile organic compounds (VOCs) were investigated at high temporal resolution from a monitoring station located in a mid-eastern area of Seoul. A total number of 587 samples were collected during December 2002 to January 2003. The measurements of VOC were conducted by a combination of on-line air sampling and thermal desorption unit (TDU) coupled with capillary GC/FID analysis. A total of five aromatic compounds (BTEX: benzene, toluene, ethylbenzene, m, p-xylene, and o-xylene) were measured routinely at hourly intervals during the whole study period. The mean concentrations of BTEX measured in our study period were found in the order: toluene (8.99 $\pm$5.38 ppb) > benzene (0.92$\pm$0.52 ppb) > m, p-xylene (0.51$\pm$0.34 ppb) > 0- xylene (0.48$\pm$0.35 ppb) > ethyl benzene (0.43$\pm$ 0.32 ppb). The BTEX concentrations were generally higher during the daytime than the nighttime, exhibiting certain patterns on a weekly basis. Results of our analysis indicate that the unusually high concentrations of toluene, while showing good correlations with other VOCs, can be a good indicator of air pollution in the study area.

• Journal of the Korean Society of Safety
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• v.21 no.3 s.75
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• pp.45-52
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• 2006

The AITs(autoignition temperatures) describe the minimum temperature to which a substance must be heated, without the application of a flame or spark, which will cause that substance to ignite. The AITs are often used as a factor in determining the upper temperature limit for processing operations and conditions for handling, storage and transportation, and in determining potential fire hazard from accidental contact with hot surfaces. The measurement AITs are dependent upon many factors, namely initial temperature, pressure, volume, fuel/air stoichiometry, catalyst material, concentration of vapor, time lag. Therefore, the AITs reported by different ignition conditions are sometimes significantly different. This study measured the AITs of benzene, toluene and xylene isomers from time lag using AS1M E659-78 apparatus. The experimental ignition delay times were a good agreement with the calculated ignition delay times by the proposed equations wtih a few A.A.D.(average absolute deviation). Also The experimental AITs of benzene, toluene, o-xylene, m-xylene and p-xylene were $583^{\circ}C,\;547^{\circ}C,\;480^{\circ}C,\;587^{\circ}C,\;and\;557^{\circ}C$, respectively.

• Journal of Preventive Medicine and Public Health
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• v.37 no.4
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• pp.321-328
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• 2004

Objectives : The purpose of this study was to investigate the effect of genetic polymorphism of cytochrome P450 2E1 (CYP2E1) and aldehyde dehydrogenase 2 (ALDH2) on the xylene metabolism. Methods : Among 247 workers, 116 were occupationally exposed to xylene and 131 were not. Workers exposed to xylene had different work such as spray, touch-up, mix & assist, and pre-treat. Questionnaire variables were age, sex, use of personal protective equipment, smoking, previous night's drinking and work duration. The urinary methylhippuric acid was measured in the urine collected in the afternoon and corrected by urinary creatinine concentration. The genotypes of CYP2E1 and ALDH2 were investigated by using PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) methods with DNA extracted from venous blood. Results : 1. The urinary concentrations of o-, m-, and p-methylhippuric acid and total methylhippuric acid in the exposed group were significantly higher than those in the non-exposed group (p<0.001). 2. In multiple regression analysis, the urinary methylhippuric acid concentration was significantly influenced by exposure grade (Job-exposure matrixes), smoking, drug use and kind of protective equipment (p<0.1). 3. Genetic polymorphism of CYP2E1 and ALDH2 did not affect urinary methylhippuric acid level in the exposed group (p>0.05). Conclusions : Exposure grade, smoking, drug use and kind of protective equipment affected urinary methylhippuric acid level, whereas genetic polymorphism of CYP2E1 and ALDH2 did not. However, further investigation for the effect of genetic polymorphism on the metabolism of xylene with a larger sample size is needed.