• 한국산업보건학회지
• /
• 제26권3호
• /
• pp.307-316
• /
• 2016

Objectives: In general, NIOSH method 5506 is most widely used for the occupational exposure measurement of PAHs, but 2-4 ring PAHs have poor desorption efficiency, especially for a filter. The purpose of this study was to determine a method to increase the desorption efficiency of 16-PAHs using an ultrasonic extraction procedure. Methods: Test samples prepared spiked XAD-2 tubes and PTFE filters in the range of $0.01-1.0{\mu}g/mL$ for desorption efficiency study. Four different extraction solvents, acetonitrile, acetone, tetrahydrofuran and dichloromethane, were tested in order to select the most suitable solvent for the extraction of the 16 PAHs. The addition of dimethyl sulfoxide and sonication time were considered in order to determine the method with the highest extraction efficiency. All samples were made in three sets and analysis was replicated seven times by HPLC. Results: Acetonitrile and acetone were the optimized as an extraction solvent and desorption efficiency of 2-ring PAHs such as naphthalene, acenaphthylene were increased 3~19% with dimethyl sulfoxide for XAD-2. Acetone was the best extraction solvent for PTFE filter and the desorption efficiency was increased 3~13% for 2- to 4-ring PAHs. The optimum sonication time was 60 minutes and desorption efficiency increased with extraction time. Conclusions: As a result, the best extraction solvent was acetone with dimethyl sulfoxide for ultrasonic extraction procedure and the desorption efficiency of this method was better than NIOSH 5506's. This study could be applied as a method for occupational exposure measurement of PAHs.

• 한국응용과학기술학회지
• /
• 제19권2호
• /
• pp.108-116
• /
• 2002

Experimental Study was carried out for benzene desorption by purge gas or evacuation in an activated carbon bed. As purge gas flow rate increased, desorption rate increased due to the higher interstitial linear gas velocity. For various purge gas flow rates, desoption curves almost got together if they were plotted against dimensionless time. At a higher flow rate, mass transfer zone became narrower. Temperature drop in the bed was more fast and severe at higher flow rates and higher outer temperature. It was found out that desorption was almost completed when the temperature in the drop of the bed returned to the initial temperature before temperature drop. Desorption by vacuum purge was completed in shorter time than desorption by purge gas. Countercurrent purge was more effective than cocurrent purge.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2000년도 추계학술대회
• /
• pp.107-118
• /
• 2000

For the last several decades, the fate of organic pollutants has been extensively studied in natural environments with emphasis on sorption and desorption phenomena. Although the mechanisms involved are not clear yet there is a consensus about the existence of hysteresis in the sorption and desorption of organic pollutants. Furthermore, it is found that hysteresis is the outcome of slow nonequilibrium sorption of organic pollutants, which results in the formation of desorption-resistant fractions of the pollutants. Desorption-resistant fractions may increase as a function of the residence time of the pollutants in the environments. Field monitoring data show a slow but continuous decline of chemicals applied to soil, followed by little or no subsequent disappearance. One plausible explanation for such resistance to biodegradation, desorption, or extraction can be attributed the gradual movement of organic pollutants to less accessible remote sites inside the matrix with time. This phenomenon has been termed sequestration or aging. The fact that some pollutants are sequestered in soil with time may have a great impact on bioremediation and risk assessment, Some portion of the resistant pollutants may still be present in the environments after bioremediation. It requires vigorous means to completely remove the aged portion that may not be further bioavailable. However, precaution should be taken since aging is not always evident. Aging seems to be soil and chemical specific.

• 한국산업융합학회 논문집
• /
• 제27권4_2호
• /
• pp.981-989
• /
• 2024

In recent years, there has been a growing focus on preserving the global environment and utilizing resources efficiently. The significance of energy conservation has led to the development of systems that recycle waste heat from factories and use eco-friendly refrigerants. This study aims to enhance the performance of adsorption-desorption systems using thermoelectric devices, which are known for their ability to convert temperature differences into electrical energy. The research focuses on improving the efficiency of these systems by integrating thermoelectric modules to cool the adsorption side and heat the desorption side, thus enhancing overall system performance. The experiments utilized a typical thermoelectric device and silica gel as the adsorbent. Key experimental parameters included varying the inlet air temperature and relative humidity on the desorption side. The results indicated that increasing the relative humidity of the inlet air on the desorption side significantly enhanced the overall mass transfer coefficient while reducing the completion time of the process. Similarly, higher inlet air temperatures led to an increase in the mass transfer coefficient and a decrease in process completion time. These findings suggest that optimizing the operational conditions of thermoelectric devices can substantially improve the performance of adsorption-desorption systems, offering potential benefits for applications in ventilation systems and other related fields.

• 한국환경과학회지
• /
• 제11권9호
• /
• pp.961-969
• /
• 2002

This study was performed : 1) to establish the experimental analysis conditions for the sorption and desorption of toxic organic contaminants to/from the activated sludge, sediment, and clay, and 2) to determine the sorption and desorption equilibrium coefficients of some representative halogenated aliphatic compounds. Through the preliminary sorption test using Azo dye, a setting of quantitative experimental conditions to determine the sorption and desorption characteristics was decided as follows; equilibration time of 180 minutes, centrifuge for 15 minutes at 5000$\times$g, and 500mg/$\ell$ of TOC concentration. The sorption and desorption characteristics of halogenated aliphatic compounds onto activated sludge, sediment and clay could be described very well using the Freundlich isotherm. The preference of the average sorption capacity of the overall compounds showed in the sequence sediment 0.26mg/g, clay 0.23mg/g, and activated sludge 0.11 mg/g. The desorption rate of the sorbed compounds onto activated sludge, sediment and clay was approximately 89.8%, 35.3%, and 66.4%, respectively.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
• /
• pp.191-194
• /
• 2005

Characteristics of sorption and desorption in soils affect chemical fate, soil-remediation time, and selection of remediation technology. The sorption and desorption behavior of atrazine and naphthalene on soils was studied. Six soils collected at Gwangju area were used as sorbents and the organic matter contents ranged from 1.28 to 5.21%. Sorption and desorption experiments were conducted and sorption distribution coefficients(Kd) of atrazine and naphthalene were nearly linear$(R^2=0.93{\sim}0.97)$. Desorption parameters were evaluated using three site desorption model included equilibrium, nonequilibrium and nondesorption sites. Non-desorbable site fraction for atrazine was evaluated, but for naphthalene it was not enumerated during the experimental period. Through the series dilution desorption experiments, non-desorpbable sites were observed for both chemicals.

• 분석과학
• /
• 제8권4호
• /
• pp.753-758
• /
• 1995

Thermal desorption/gas chromatography/mass selective detection method using Tenax cartridges for the determination of gaseous polycyclic aromatic hydrocarbons(PAH) is described. Glass fiber filter can collect only PAH in particulate. Gaseous PAH may penetrate the filter. Glass cartridge packed Tenax-GC was uses fur adsorption of gaseous PAH. The air of inhalation zone was collected fur 2-10 hours. Cartridges were thermally desorbed in the reverse direction to sample flow. The desorption conditions were as follows; desorption temperature; $300^{\circ}C$; desorption time; 20min; column head pressure; 30psi; inlet split vent; closed during desorption.

• 한국환경과학회지
• /
• 제11권7호
• /
• pp.737-742
• /
• 2002

Sorption and desorption is an important phenomenon to determine the fate of halogenated aliphatic hydrocarbons in the aqueous phase. This study was conducted to develope a predictive equation capable of estimating the sorption and desorption potentials of halogenated aliphatic hydrocarbons onto the sludge from activated process, sediment, and clay. It has shown that the sorption and desorption parameters can be accurately estimated using Quantitative Structural Activity Relationship(QSAR) models based on molecular connectivity indexes of test compounds. The QSAR model could be applied to predict the sorption and desorption capacity of the other halogenated aliphatic hydrocarbons. The QSAR modeling would provide a useful tool to predict the sorption and desorption capacity without time-consuming experiments.

• 한국광물학회지
• /
• 제22권4호
• /
• pp.289-295
• /
• 2009

카올리나이트 KGa-1b (표준 점토)의 인산염 탈착 특성을 규명하기 위하여 벳치(batch) 흡착-탈착 실험을 실시하였으며, 탈착 과정은 연속추출법에 따라 pH 4에서 시행하였다. 인의 함량은 UV 분광분석기를 시용하여 측정하였으며, 이 때 파장은 820 nm를 이용하였다. 카올리나이트의 인산염 흡착-탈착 반응은 비가역적으로 일어나며, 흡착된 대부분의 인산염은 고착되는 경향을 나타낸다. 인산염 탈착 등온선은 반응 시간이 짧은 경우 프로인드리히 등온선에, 반응 시간이 긴 경우 탬킨 등온선에 더 일치하는 경향을 보인다. 인산염 탈착 반응은 초기의 빠른 반응과, 후기의 느린 반응으로 구분된다. 흡착된 인산염의 농도가 높아질수록 탈착률은 감소하는 경향을 보이며, 탈착 시간이 길어지면 탈착률은 감소하는 경향을 보여준다.

• Carbon letters
• /
• 제2권1호
• /
• pp.44-54
• /
• 2001

The characteristics of adsorption and desorption of benzene and toluene were investigated at a fixed bed packed with the activated carbon and activated carbon fiber. Through breakthrough experiments under various feed concentration conditions, it was found that the slope of mass transfer zone and the tailing in the breakthrough curves were different from the feed conditions due to different heats of adsorption. In hot nitrogen desorption, the regeneration time and mass transfer zone of the toluene desorption curve were longer than those of the benzene desorption curve because of the difference in adsorption affinity. With an increase in the regeneration temperature, the height of roll-up and the sharpness of desorption curves increased but the regeneration times decreased. The adsorption capacities of the activated carbon and activated carbon fiber after three-time thermal regenerations decreased about 25% and 37% for benzene and 18% and 25% for toluene, respectively. To investigate the effect of the regeneration temperature on the energetic efficiency, the characteristic desorption temperatures of toluene and benzene were investigated by calculating purge gas consumption and temperature.