• Title, Summary, Keyword: water vapor adsorption

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Kinetics of water vapor adsorption by vacuum-dried jujube powder

  • Lee, Jun Ho;Zuo, Li
    • Korean Journal of Food Preservation
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    • v.24 no.4
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    • pp.505-509
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    • 2017
  • Water vapor adsorption kinetics of vacuum-dried jujube powder were investigated in temperature and relative humidity ranges of 10 to $40^{\circ}C$ and 32 to 75%, respectively. Water vapor was initially adsorbed rapidly and then reached equilibrium condition slowly. Reaction rate constant for water vapor adsorption of vacuum-dried jujube powder increased with an increase in temperature. The temperature dependency of water activity followed the Clausius-Clapeyron equation. The net isosteric heat of sorption increased with an increase in water activity. Good straight lines were obtained with plotting of $1/(m-m_0)$ vs. 1/t. It was found that water vapor adsorption kinetics of vacuum-dried jujube powder was accurately described by a simple empirical model, and temperature dependency of the reaction rate constant followed the Arrhenius-type equation. The activation energy ranged from 50.90 to 56.00 kJ/mol depending on relative humidity. Arrhenius kinetic parameters ($E_a$ and $k_0$) for water vapor adsorption by vacuum-dried jujube powder showed an effect between the parameters with the isokinetic temperature of 302.51 K. The information on water vapor adsorption kinetics of vacuum-dried jujube powder can be used to establish the optimum condition for storage and processing of jujube.

Kinetics of Initial Water Vapor Adsorption by Inonotus obliquus Mushroom Powders

  • Lee, Min-Ji;Seog, Eun-Ju;Lee, Jun-Ho
    • Preventive Nutrition and Food Science
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    • v.12 no.2
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    • pp.111-114
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    • 2007
  • Water vapor adsorption kinetics of Inonotus mushroom powders were investigated in temperature and water activity ranges of 20 to 40$^{\circ}C$ and 0.30 to 0.81, respectively. Initial water vapor adsorption rate of mushroom powders increased with increases in temperature and water activity. The temperature dependency of water activity followed the Clausius-Clapeyron equation. The net isosteric heat of sorption increased with an increase in water activity. Water vapor adsorption kinetics of the mushroom powders can be well described by a simple empirical model. Temperature dependency of the reaction rate constant followed the Arrhenius relationship. The activation energy ranged from 56.86 to 91.35 kJ/mol depending on water activity. Kinetic compensation relationship was observed between k$_o$ and E$_a$ with the isokinetic temperature of 790.27 K.

Kinetics of Water Vapor Adsorption by Chitosan-based Nanocomposite Films

  • Seog, Eun-Ju;Zuo, Li;Lee, Jun-Ho;Rhim, Jong-Whan
    • Food Science and Biotechnology
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    • v.17 no.2
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    • pp.330-335
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    • 2008
  • Water vapor adsorption kinetics of 3 different types of chitosan-based films, i.e., control chitosan, chitosan/montmorillionite (Na-MMT), and chitosan/silver-zeolite (Ag-Ion) nanocomposite films, were investigated at temperature range of $10-40^{\circ}C$. In all the films, water vapor is initially adsorbed rapidly and then it comes slowly to reach equilibrium condition. Reasonably good straight lines were obtained with plotting of 1/($m-m_0$) vs. l/t. It was found that water vapor adsorption kinetics of chitosan-based films was accurately described by a simple empirical model and the rate constant of the model followed temperature dependence according to Arrhenius equation. Arrhenius kinetic parameters ($E_a$ and $k_o$) for water vapor adsorption by chitosan-based films showed a kinetic compensation effect between the parameters with the isokinetic temperature of 315.52 K.

Water Vapor Adsorption on Soils. -I. Surface areas and adsorption energies as calculated by the BET and a new Aranovich theories (토양에서의 수증기 흡착 -I. BET와 Aranovich식에 의한 한국토양에서의 수증기흡착 등온식으로 토양표면적과 흡착에너지 산정)

  • Jozefaciuk, G.;Shin, Jae-Sung
    • Korean Journal of Soil Science and Fertilizer
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    • v.29 no.2
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    • pp.86-91
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    • 1996
  • Water vapor adsorption isotherms were measured for samples of the A horizons of five typical Korean soils. The experimental data were fitted to the BET and Aranovich adsorption equations. The adsorption isotherms studied followed the BET equation for the relative water vapor pressures in 0.03-0.33 range and the Aranovich equation in 0.03-0.6 range. The calculated surface areas were higher for Aranovich than for BET and opposite relations were found for adsorption energies. For the description of the water adsorption on soils, the use of the Aranovich theory is recommended.

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Adsorption Characteristics of Water Vapor on Zeolite (Zeolite의 수증기 흡착특성)

  • Lee, Song-Woo;Na, Young-Soo;An, Chang-Doeuk;Lee, Min-Gyu
    • Journal of Environmental Science International
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    • v.20 no.5
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    • pp.667-672
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    • 2011
  • The purpose of this work is to present the experiment results by a dynamic adsorption of water vapor on pelletized zeolites (ADZ300, ADZ400, and ADZ500) in fixed bed. The breakthrough curves of water vapor with several different concentrations and temperature in the range of 25~45 $^{\circ}C$ on zeolite bed were investigated. In the same conditions, the breakthrough time on ADZ400 and ADZ500 were little longer than ADZ300, and the equilibrium adsorption capacity on ADZ500 was highest. The higher the concentration of water vapor was, the faster the breakthrough time was, and the slope of breakthrough curves showed a tendency to increase. The faster the flow rate of water vapor was, the faster the breakthrough time was relatively, but variations between flow rate and breakthrough time did not have a proportional relationship. The breakthrough curve maintained constant gradient in spite of variation of flow rate in the same concentration. The temperature rise in zeolite bed by adsorption heat was occurred in the early stage of adsorption. After water molecule layers were formed on the surface of zeolite, the temperature was slowly cooled by water vapors continuously flowed in as constant temperature. The greater the concentration of water vapor and adsorption temperature were, the temperature difference in zeolite bed was increased.

Water Vapor Adsorption on Soils II. Estimation of Adsorption Energy Distributions Using Local BET and Aranovich Isotherms (토양에서의 수증기 흡착 II. BET와 Aranovich 등온식을 이용한 한국토양에서 수증기 흡착에너지 분포의 추정)

  • Jozefaciuk, G.;Shin, Jae-Sung
    • Korean Journal of Soil Science and Fertilizer
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    • v.29 no.3
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    • pp.218-225
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    • 1996
  • Using water vapor adsorption data foe some typical Korean soils. we calculated the adsorption energy distribution functions and average adsorption energies for these soils using theory of adsorption on hetergeneous surfaces. As a local adsorption models the BET and a new Aranovich equations were applied. The distribution functions were broad, indicating rather high energetic inhomogeneity of the surface.

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Comparison of Adsorption Characteristics on Zeolite 13X and Silica-aluminar (제올라이트 13X와 실리카-알루미나의 흡착특성 비교)

  • Lee, Song-Woo;Na, Young-Soo;An, Chang-Doeuk;Lee, Min-Gyu
    • Journal of Environmental Science International
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    • v.20 no.6
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    • pp.729-736
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    • 2011
  • This work is to compare the experiment results by a continuous fixed-bed adsorption of water vapor, acetone vapor, and toluene vapor on zeolite 13X (SAU) and silica-alumina (SAK). SAU and SAK have very different pore structure but similar composition as inorganic adsorbent. The relationship between the equilibrium adsorption capacity and specific pore size range were studied. Adsorption of water vapor was more suitable on SAU than SAK because SAU has relatively more developed pores around $5\;\AA$ than SAK in the pore range of $10\sim100\;\AA$. Adsorption of acetone vapor was more suitable on SAK than SAU because SAK has relatively more developed pores around $5\sim10\;\AA$ than SAK in the pore range of less than $10\;\AA$. Adsorption of toluene vapor was more suitable on SAK than SAU because SAK has relatively more developed pores in the pore range of $10\sim100\;\AA$ than SAK. Adsorption capacity of the adsorbent was closely related to the surface area generated in the specific pore size region. But it was difficult to distinguish the relationships between adsorption capacity and micro area, and the external surface area of adsorbent.

Effect of Hydrophobic Coating on Silica for Adsorption and Desorption of Chemical Warfare Agent Simulants Under Humid Condition

  • Park, Eun Ji;Cho, Youn Kyoung;Kim, Dae Han;Jeong, Myung-Geun;Kim, Young Dok
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.148.2-148.2
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    • 2013
  • We prepared hydrophobic PDMS-coated porous silica as pre-concentration adsorbent for chemical warfare agents (CWAs). Since CWAs can be harmful to human even with a small amount, detecting low-concentration CWAs has been attracting attention in defense development. Porous silica is one of the promising candidates for CWAs pre-concentration adsorbent since it is thermally stable and its surface area is sufficiently high. A drawback of silica is that adsorption of CWAs can be significantly reduced due to competitive adsorption with water molecule in air since silica is quite hydrophilic. In order to solve this problem, hydrophobic polydimethylsiloxane (PDMS) thin film was deposited on silica. Adsorption and desorption of chemical warfare agent (CWA) simulants (Dimethylmethylphosphonate, DMMP and Dipropylene Glycol Methyl Ether, DPGEM) on bare and PDMS-coated silica were studied using temperature programed desorption (TPD) with and without co-exposing of water vapor. Without exposure of water vapor, desorbed amount of DMMP from PDMS-coated silica was twice larger than that from bare silica. When the samples were exposed to DMMP and water vapor at the same time, no DMMP was desorbed from bare silica due to competitive adsorption with water. On the other hand, desorbed DMMP was detected from PDMS-coated silica with reduced amount compared to that from the sample without water vapor exposure. Adsorption and desorption of DPGME with and without water vapor exposing was also investigated. In case of bare silica, all the adsorbed DPGME was decomposed during the heating process whereas molecular DPGME was observed on PDMS-coated silica. In summary, we showed that hydrophobic PDMS-coating can enhance the adsorption selectivity toward DMMP under humid condition and PDMS-coating also can have positive effect on molecular desorption of DPGME. Therefore we propose PDMS-coated silica could be an adequate adsorbent for CWAs pre-concentration under practical condition.

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Adsorption Characteristics of Toluene Vapor According to Pore Size Distribution of Activated Carbon (활성탄의 세공분포에 따른 Toluene Vapor의 흡착특성)

  • Lee Song-Woo;Kwon Jun-Ho;Kang Jeong-Hwa;Na Young-Soo;An Chang-Doeuk;Yoon Young-Sam;Song Seung-Koo
    • Journal of Environmental Science International
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    • v.15 no.7
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    • pp.695-699
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    • 2006
  • This study is to investigate the relationship between pore structures of activated carbons and adsorption characteristics of toluene vapor using dynamic adsorption method. The surface areas of below $10{\AA}$ in the pore diameter of activated carbons used in this experiment were in the range of 72 -93 % of total cumulative surface area and the toluene vapor equilibrium adsorption capacities were in the range of 350 - 390mg/g. Activated carbons having larger toluene adsorption capacity than the compared activated carbons had relatively pores in the pore diameter range of $7-10{\AA}$. Linear relationship between equilibrium adsorption capacity and cumulative sur- face area was in the diameter range of over $7{\AA}$. It was thought that toluene vapor was relatively well adsorbed on surfaces of pores of over $7{\AA}$.

Water Vapor Adsorption and Hydrogen Peroxide Decomposition on Date Pit Carbonization Products

  • Youssef, A.M.;El-Nabarawy, Th.;Ahmed, S.A. Sayed;Rashwan, W.E.
    • Carbon letters
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    • v.6 no.4
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    • pp.227-233
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    • 2005
  • Carbonization products C1, C2, C3, C4 and C5 were prepared by the carbonization of date pit in limited air, at 500, 600, 700, 800 and $1000^{\circ}C$, respectively. C1-V-600, C3-V-600, C1-V-1000 and C3-V-1000 were prepared by thermal treatment of C1 and C3 under vacuum at 600 and $1000^{\circ}C$. The textural properties were determined from nitrogen adsorption at 77 K and from carbon dioxide adsorption at 298 K. The surface pH, the FTIR spectra and the acid and base neutralization capacities of some carbons were investigated. The amounts of surface oxygen were determined by out-gassing the carbon-oxygen groups on the surface as $CO_2$ and CO. The adsorption of water vapor at 308 K on C1, C2, C3 and C4 was measured and the decomposition of $H_2O_2$ at 308 K was also investigated on C1, C2, C3, C4 and C5. The surface area and the total pore volume decreased with the rise of the carbonization temperature from 500 to $1000^{\circ}C$. The adsorption of water vapor is independent on the textural properties, while it is related to the amount of acidic carbon-oxygen groups on the surface. The catalytic activity of $H_2O_2$ decomposition does not depend on the textural properties, but directly related to the amount of basic carbon-oxygen complexes out-gassed as CO, at high temperatures.

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