• Journal of Environmental Health Sciences
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• v.19 no.3
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• pp.17-21
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• 1993

Characteristics of a downflow anaerobic packed bed reactor with raschig ring ceramics as a packing were measured and discussed for the basic evaluation of the process. A synthesized glucose substrate wastewater were used as a feed and process characteristics such as pH, biogas production, composition of produced gas, COD removal and VSS were measured with the hydraulic retention time (HRT) changing from 0.25 to 2 days. As a result, this type of reactor was applicable in continuous operation within the given HRT range and the transient period approaching the steady state was about 20 days. The content of methane in produced gas increase with HRT was always high above 50% enough to use as energy source. The COD removal efficiency increased gradually as HRT increased. The axial profile of VSS concentration in the reactor usually showed the maximum at the lower region and the minimum at the middle. The VSS concentration at the upper region and the exit appeared similarly. However, at 0.25 day of HRT, the VSS concentration of effluent became higher than that of the upper region. Therefore the optimum HRT of this reactor occurred about 0.5 day, at which the production of methane began to be just stabilized and loss of VSS and COD removal were resonable.

• Journal of the Korean Applied Science and Technology
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• v.27 no.3
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• pp.318-324
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• 2010

In this study, commercial pellet type sorbents for the collection of $CO_2$ from a local municipal waste incinerator were prepared and characterized in terms of adsorption efficiency by varying the operating conditions of a field process. The concentration of $CO_2$ in the flue gas ranged from 8 to 10%, which entered the test packed bed. As a result of this experiment, the sorbent procured from A-company, which is mainly composed of calcium compounds, showed the highest adsorption efficiency. The regeneration efficiency was fairly low, however. It also was found that based on adsorption breakthrough time, the relatively low flow rate of 10 LPM into the bed allowed higher collection efficiency. The higher flow rate of 40 LPM, on the other hand, tended to decrease the retention of the adsorption.

• Journal of environmental and Sanitary engineering
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• v.5 no.2
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• pp.63-80
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• 1990

A sensitive and simple analytical system for the simultaneous determination of residual oxytetracycline, tetracycline, and doxycycline in honey was described, and that the analytical method for determination of residual propionic acid in honey was established. Experimental subjects were purchased four kinds of honey, native kind honey, acaccia honey, mixed floral honey, chestnut honey in Kyung Sang Nam Do. Several microbiological methods are available to determine tetracycline antibiotecs(TCs) in foods but their precision apears to be variable and the specificity is questionable. These methods are considered to be not suitable for analysis of tetracycline antibiotics in honey because honey itself has bacteriostatic action. For determination of tetracycline antibiotics in honey, therefore the High Performance Liquid Chromatography(HPLC) method was applied, and the propionic acid were determined by Gas Chromatography(5.C). Ethylacetate, as an extract solvent, was found to be suitable for seperation of TCs in honey, but methanol and acetone were not. The recoverly rate of Oxytetracycline(OTC), Tetracycline(TC), Doxycycline(DC) from honey spiked at a level of 10 $\mu $g/g were 97%, 89%, and 91%, respectively. The cailbration curve in TCs was linear expression from 2$\mu $g/ml to 10$\mu $g/ml. As the results of analysis, the residual tetracycline antibiotics were not detected in the 100 samples of honey. The recovery rate of propionic acid from honey spiked at level of 10$\mu $g/g was 98.3% , and the calibra lion curves were linear expression from 21$\mu $g/ml to 101$\mu $g/ml. As the results of analysis, the residual propionic acid was not detected in the 100 samples of honey. Retention time(min) of OTC, DC, and TC were 3.35, 4.61, and 5.30 minutes at the conditions of table 2, respectively, and retention time(min) of propionic acid was 3.50 minutes at the conditions of table 3. The residual TCs and propionic acid were not detected in the 100 samples of honey, but there is a possibility that antibiotics or propionic acid will be to remain in honey if they are used during product period in order to prevent putrefaction of honey-bee.

• Environmental Engineering Research
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• v.21 no.3
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• pp.291-296
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• 2016

Application of photocatalytic nanoparticles has been recently gaining an increased attention as air purifying material for sustainable urban development. The present work reports the photocatalytic removal of gaseous phase nitrogen oxides ($NO_x$) using $TiO_2$-coated zeolite to be applied as a filter media for the urban green infrastructure such as raingardens. The $TiO_2$-coated zeolite was synthesized by simple wet chemistry method and tested in a continuous-flow photo-reactor for its removal efficiency of $NO_x$ under different conditions of the weight percentage of $TiO_2$ coated on the zeolite, and gas retention time. The removal efficiency of $NO_x$ in general increased as the weight percentage of $TiO_2$ coated on the zeolite increased up to 15-20%. Greater than 90% of $NO_x$ was removed at a retention time of one minute using the $TiO_2$-coated zeolite ($TiO_2$ weight percentage = 20%). Overall, $TiO_2$-coated zeolite showed greater efficiency of $NO_x$ removal compared to $TiO_2$ powder probably by providing additional reaction sites from the porous structure of zeolite. It was presumed that the degradation of $NO_x$ is attributed to both the physical adsorption and photocatalytic oxidation that could simultaneously occur at the catalyst surface.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.961-965
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• 2007

In this study, degradation of carbohydrates and composition of fermentative products were investigated in semi-continuous acid fermenter varying hydraulic retention time (HRT). Rice soup was used as a sole substrate for the acid fermentation. Solubilization efficiency of the substrate was higher than 70% for all HRT, however the gas conversion was ignorable implying that most of organic contents in the influent remained in the form of volatile fatty acids (VFAs) and ethanol after acid fermentation. The VFAs were the predominant product and the VFAs conversion increased as the HRT decreased. The VFAs conversion reached the maximum value at 12 hr HRT accounting for 70% of the influent COD. Similar to VFAs, ethanol conversion was increased with the decrease of HRT and the maximum ethanol conversion efficiency was 8% at the HRT of 12 hr. Composition of VFAs was markedly dependent on HRT. As HRT increased, the composition of acetic acid was increased as a product of acetogenesis from butyrate, valerate and ethanol. This study demonstrated that HRT affected acid fermentation of a carbohydrate containing organic wastes producing VFAs and ethanol which could be effectively used to compensate the lack of carbon in wastewater for biological nutrient removal.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.121-128
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• 1998

In fields of operating or handling a hydrogen isotope facility, and of the technology for nuclear fusion source management, gas chromatography has been used as one of the practical techniques lot separation and enrichment of hydrogen isotopic gases including tritium. Chromatographic separation experiments of the hydrogen isotope mixture (hydrogen, deuterium and tritium) were carried out by use of a commercially available gas chromatograph. An aliquot of gas sample was injected by a specially designed vacuum sampler into the stream of inert carrier gas which went through the separation column under liquid nitrogen temperature. The complete separation of hydrogen isotopic molecules was observed with an alumina adsorbent partially deactivated by coating with 10% manganese chlorine. In addition, fairly good separation conditions were obtained without any appearance of nuclear spin isomers with shorter retention time, which would be available for the practical applications of the hydrogen isotope separation and enrichment.

• The Korean Journal of Ecology
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• v.20 no.6
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• pp.397-403
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• 1997

The monoterpenes and sesquiterpenes are analysed in the leaf and stem of Chrysanthemum boreale using gas chromaltography-mass spectrometry (GC-MS). The total amount of sesquiterpenes are always higher than monoterpenes in both leaf (2.0-3.4 times) and stem (1.6-8.3 times). The mono- and sesquiterpenes yields of the leaf are higher than the stem. There was no significant difference among the leaf developmental stages, while those of stem were varied. Seventeen monoterpenes and 9 sesquiterpenes compound in this plants comprised more than 5% of the mean total monoterpenes and the total sesquiterpenes in each dates. Among leaf monoterpenes, the concentration of (+)-Limonene and unknown compound no. 13 (Retention time, R.T.=17.28) varied significantly during leaf growing season, and the concentrafion of unknown compound no. 7 (R.T.=35.04) and no. 9(R.T.=35.71) varied in the leaf sesquiterpenes. Similarly the results from the leaf, the concentration of five monoterpenes in stem also varied significantly during maturing period, and much varied in seven compounds of stem sesquiterpene. The major sesquiterpenes of leaf and stem were ${\alpha}-Humulene$ and compound no. 2(R.T.=26.19).

• The Korean Journal of Food And Nutrition
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• v.12 no.2
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• pp.119-123
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• 1999

Test of the optimum condition of solid phase micro extraction(SPME) was performed by use of 5 vol-atile components in dilute aqueous solution. Volatile components of Sancho(Zanthoxylum schinifolium) were isolated by SPME method and were analyzed by GC/MSD and compared with volatile compone-nts isolated by simultaneous distillation extraction (SDE) method. Total 31 components were identified by comparing gas chromatography retention time and mass spectral data. The major compounds were limonene geranyl acetate $\beta$-phellandrene phellandral mycene linalool rose oxide caproic acid and caprylic acid SPME sampling procedure was found to be a good method for qualitative analysis of the volatile components.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.E1
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• pp.13-20
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• 2002

The electrical and chemical properties of the dielectric barrier discharge (DBD) process for the benzene removal were investigated. The benzene removal was initiated with the applied voltage higher than the discharge onset value. The removal efficiency over 95 % was obtained at approximately 1.6 kJ lite $r^{r-1}$ of the electrical energy density. The increase of the inlet concentration decreased the removal efficiency. However, the benzene decomposition rate increased with the inlet concentration . While the increase of the gas retention time enhanced the removal efficiency, the decomposition rate decreased. Identification of the optimum condition between the decomposition rate and the removal efficiency is required for field applications of the DBD process.s.

• Environmental Analysis Health and Toxicology
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• v.15 no.1_2
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• pp.45-51
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• 2000

Analytical method of 4-nitrotoluene (4-NT) in water was developed by 9as chromatography/mass selective detector/selected ion monitoring (GC/MSD/SIM). 4-NT was extracted with diethyl ether. Organic layer was washed with 5 % sodium chloride solution. The influence of solvent and evaporation condition on extraction of 4-NT were examined. The retention time of 4-NT peak was 7.72 min. Coefficient of variation (CV) of 4-NT (ng) within day and day-to-day was ranged from 7.0 to 14.6% and from 7.7 to 20.8%, respectively. Recovery of 4-NT was ranged from 84 to 109%, and detection limit of 4-H was lese than 1 ng/㎖.