• 한국지반환경공학회 논문집
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• 제15권12호
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• pp.61-69
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• 2014

Carboxymethyl-${\beta}$-cyclodextrin(${\beta}$-CMCD)은 소수성과 친수성의 성질을 모두 가지고 있는 생분해성 계면활성제로 복합오염토양의 동시 처리에 적용이 가능한 장점이 있다. 본 연구에서는 코발트(Co), 스트론튬(Sr) 및 세슘(Cs) 등의 방사성 핵종 중금속으로 오염된 토양에서 이들의 탈착 거동을 살펴보고, 탈착제로서 CMCD의 효과를 평가하였다. 탈착속도 실험에서 Co, Sr 및 Cs 모두 1~3시간 이내에 탈착평형에 도달하였으며, 카올린에서의 탈착률이 자연토양에서 보다 높게 나타났다. 또한 탈착용액으로 CMCD를 2 g/L를 첨가한 경우 탈착률이 5~20 %가량 증가하였으며, 핵종 중금속별 탈착률은 Co > Cs > Sr 순으로 나타났다. 탈착실험 결과를 다양한 탈착속도 모델에 적용한 결과, pseudo-second order kinetic model을 가장 잘 따르는 것으로 나타났으며, 탈착속도는 Cs > Co > Sr 순으로 나타났다. 흡/탈착 간 이력현상은 Sr > Co > Cs 순으로 탈착속도가 느릴수록 이력현상이 커지는 것으로 나타나, 탈착속도가 흡/탈착 간 이력현상을 야기하는 주요 요인 중 하나로 판단되었다. CMCD의 주입으로 탈착량이 증가하고 흡/탈착 간 이력현상이 감소하는 효과를 보였으나, 과량 주입 시에도 토양에 흡착된 핵종 중금속을 완전히 탈착시키지는 못하는 것으로 평가되었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권6호
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• pp.79-94
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• 2011

Black carbon (BC), a kind of high surface area carbonaceous material (HSACM), was isolated from Andong lake sediment. Sorption and desorption kinetics of naphthalene (Naph) and phenanthrene (Phen) in organic carbon (OC) and BC in the Andong lake sediment were investigated. Several kinetic models such as one-site mass transfer model (OSMTM), two-compartment first-order kinetic model (TCFOKM), and a newly proposed modified two-compartment first-order kinetic model (MTCFOKM) were used to describe the sorption and desorption kinetics. The MTCFOKM was the best fitting model. The MTCFOKM for sorption kinetics showed that i) the sorbed amounts of PAHs onto BC were higher than those onto OC, consistent with BET surface area; ii) the equilibration time for sorption onto BC was longer than those onto OC due to smaller size of micropore ($11.67{\AA}$) of BC than OC ($38.18{\AA}$); iii) initial sorption velocity of BC was higher than OC; and iv) the slow sorption velocity in BC caused the later equilibrium time than OC even though the fast sorption velocity was early completed in both BC and OC. The MTCFOKM also described the desorption of PAHs from the OC and BC well. After desorption, the remaining fractions of PAHs in BC were higher than those in OC due to stronger PAHs-BC binding. The remaining fractions increased with aging for both BC and OC.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권4호
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• pp.38-52
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• 2011

Sorption and sequential desorption experiments were conducted for Zn using a natural soil (NS) in background status by aging (1, 30 and 100 days). The sorption isotherm showed that Zn had high sorption capacity but low sorption affinity in NS. Sequential desorption was biphasic with appreciable amount of sorbed Zn residing in the desorption-resistant fraction after several desorption steps. The biphasic desorption behavior of Zn was characterized by a biphasic desorption model that includes a linear term to represent labile or easily-desorbing fraction and a Langmuirian-type term to represent desorption-resistant fraction. The biphasic desorption model indicated that the size of the maximum capacity of desorption-resistant fraction ($q^{irr}_{max}$) increased with aging in NS. Desorption kinetics and desorption-resistance of Zn in the soils collected from mine tailings (MA, MB and MC collected from surface, subsurface soils and mine waste, respectively) were investigated and compared to the bioavailability to earthworm (Eisenia fetida). Desorption kinetic data of Zn were fitted to several desorption kinetic models. The ratio ($q_{e,d}/q_0$) of remaining Zn at desorption equilibrium ($q_{e,d}$) to initial sorbed concentration ($q_0$) was in the range of 0.53~0.90 in the mine tailings which was higher than that in NS, except MA. The sequential desorption from the mine tailings with 0.01M Na$NO_3$ and 0.01M $CaCl_2$ showed that appreciable amounts of Zn are resistant to desorption due to aging or sequestration. The SM&T (Standard Measurements and Testing Programme of European Union) analysis showed that the sum of oxidizable (Step III) and residual (Step IV) fractions of Zn was linearly related with its desorption-resistance ($q^{irr}_{max}$) determined by the sequential desorption with 0.01M Na$NO_3$ ($R^2$= 0.9998) and 0.01M $CaCl_2$ ($R^2$= 0.8580). The earthworm uptake of Zn and the desorbed amount of Zn ($q_{desorbed}$ = $q_0-q_{e,d}$) in MB soil were also linearly related ($R^2$ = 0.899). Our results implicate that the ecological risk assessment of heavy metals would be possible considering the relation between desorption behaviors and bioavailability to earthworm.

• 한국환경과학회지
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• 제28권6호
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• pp.561-570
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• 2019

A zeolitic material (Z-Y2) was synthesized from Coal Fly Ash (CFA) using a fusion/hydrothermal method under low-alkali condition (NaOH/CFA = 0.6). The adsorption performance of the prepared zeolite was evaluated by monitoring its removal efficiencies for Sr and Cs ions, which are well-known as significant radionuclides in liquid radioactive waste. The XRD (X-ray diffraction) patterns of the synthesized Z-Y2 indicated that a Na-A type zeolite was formed from raw coal fly ash. The SEM (scanning electron microscope) images also showed that a cubic crystal structure of size $1{\sim}3{\mu}m$ was formed on its surface. In the adsorption kinetic analysis, the adsorption of Sr and Cs ions on Z-Y2 fitted the pseudo-second-order kinetic model well, instead of the pseudo-first-order kinetic model. The second-order kinetic rate constant ($k_2$) was determined to be $0.0614g/mmol{\cdot}min$ for Sr and $1.8172g/mmol{\cdot}min$ for Cs. The adsorption equilibria of Sr and Cs ions on Z-Y2 were fitted successfully by Langmuir model. The maximum adsorption capacity ($q_m$) of Sr and Cs was calculated as 1.6846 mmol/g and 1.2055 mmol/g, respectively. The maximum desorption capacity ($q_{dm}$) of the Na ions estimated via the Langmuir desorption model was 2.4196 mmol/g for Sr and 2.1870 mmol/g for Cs. The molar ratio of the desorption/adsorption capacity ($q_{dm}/q_m$) was determined to be 1.44 for Na/Sr and 1.81 for Na/Cs, indicating that the amounts of desorbed Na ions and adsorbed Sr and Cs ions did not yield an equimolar ratio when using Z-Y2.

• 산업기술연구
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• 제1권
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• pp.47-51
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• 1981

A Kinetic model of desorption of hydrogen in $Dy_2Co_7-H$ system has been suggested and rate equation of each step of the model has been compared with experimental results. The reat controlling step was hydrogen recombination in metal surface. The activation energy of over-all reaction was about 23kcal/mole.

• Journal of the Korean Wood Science and Technology
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• 제47권5호
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• pp.557-566
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• 2019

Radial and tangential water diffusion in Eucalyptus globulus wood was investigated using three mature trees from a forest in Khemis Sahel (North Morocco). Absorption and desorption kinetics experiments were conducted at ambient temperature ($25^{\circ}C$) and $30^{\circ}C$, respectively, and a relative humidity of 60%. The diffusion coefficients in the two directions were determined under imposed hygrothermal conditions; they were greater in the radial direction for the absorption as well as desorption processes. Convective drying under load, preceded by reconditioning and followed up by balancing, revealed the drying conditions that corresponded to the appropriate drying schedules for E. globulus wood. This was verified by measuring the cracks and bowsbefore and after drying of boards.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.125-132
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• 2006

Transient kinetics of $NH_3$ adsorption/desorption and of SCR(selective catalytic reduction) of NO with $NH_3$ were studied over vanadium based catalysts, such as $V_2O_5/TiO_2$ and $V_2O_5-WO_3/TiO_2$. In the present catalytic reaction process, NO adsorption is neglected while $NH_3$ is strongly chemisorbed on the catalytic surface. Accordingly, it is ruled out the possibility of a reaction between strongly adsorbed $NH_3$ and NO species in line with the hypothesis of an Eley-Rideal mechanism. The present kinetic model assumes; (1) non-activated $NH_3$ adsorption, (2) Temkin-type $NH_3$ coverage dependence of the desorption energy, (3) non-linear dependence of the SCR reaction rate on the $NH_3$ surface coverage. Thus, the surface heterogeneity for adsorption/desorption of $NH_3$ is taken into account in this model. The present study extends the pure chemical kinetic model based on a powdered-phase catalytic system to the chemico-physical one applicable to a realistic monolith reactor.

• 청정기술
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• 제16권1호
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• pp.33-38
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• 2010

시화/반월 산단 내 활성탄 흡착탑을 사용하는 대표적인 업체에서 수거한 폐활성탄의 탈착특성 및 열량특성을 조사하였다. 열중량분석기를 이용하여 폐활성탄의 탈착반응특성을 조사하였다. 탈착특성 데이터를 바탕으로 탈착반응특성 비교에 중요한 요소인 반응차수 및 활성화에너지를 구하기 위하여 Freeman-Carroll법을 사용하여 반응차수와 활성화에너지 값을 구하였다. 또한 폐활성탄에 흡착되어 있는 휘발성 유기 화합물의 총탄화수소 배출특성을 이용하여 톨루엔을 기준으로 한 휘발성 유기 화합물의 열량을 계산하였다. 본 연구에서 는 반응차수가 0.1~0.8, 활성화에너지가 6.8~26.4 kJ/mol로 나타났으며, 열량은 업체별로 0.4~10.7 kcal/kg으로 나타났다.

• Mass Spectrometry Letters
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• 제15권1호
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• pp.54-61
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• 2024

An improved voltage modulation method (VMM) was used to control the heat release and adsorption properties of the adsorbent. In this work, the voltage and flux modulation methods were considered under unified experimental conditions of dissociative surface ionization (SI) of polyatomic organic molecules, the criteria were found when under VMM conditions the current relaxation of SI carries information about the kinetic properties of thermal desorption of ionizable dissociation particles arriving on the surface of polyatomic molecules. Conditions were found under which the relaxation of the ionic current in the flux modulation method is determined by the kinetics of the heterogeneous dissociation reaction of the original polyatomic molecules. The values of the thermal desorption rate constant K⁺ and the activation energy E⁺ obtained with VMM for desorption of (CH₃)₂NCH⁺₂ ions with m/z 58 by adsorption of imipramine and amitriptyline molecules agree well with each other and with the results for the desorption of the same ions by adsorption of other molecules. This confirms one of the basic conditions for the equilibrium process SI - the a degree (β coefficient) of the same particles SI on the same emitter surface is the same and does not depend on the way these particles are formed on the emitter surface.

• Advances in environmental research
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• 제1권3호
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• pp.223-236
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• 2012

Biosorption of methylene blue (MB) from aqueous solution was studied with respect to the point of zero charge of coconut husk, dye concentration, particle size, pH, temperature, as well as adsorbent and NaCl concentration using coconut husk biomass. Amongst Langmuir and Freundlich adsorption isotherms studied, Langmuir adsorption isotherm showed better agreement. Pseudo second order kinetics model was found to be more suitable for data presentation as compared to pseudo first order kinetics model. Also, involvement of diffusion process was studied using intraparticle diffusion, external mass transfer and Boyd kinetic model. Involvement of intraparticle diffusion model was found to be more relevant (prominent) as compared to external mass transfer (in) for methylene blue biosorption by the coconut husk. Moreover, thermodynamic properties of MB biosorption by coconut husk were studied. Desorption of methylene blue from biomass was studied with different desorbing agents, and the highest desorption achieved was as low as 7.18% with acetone, which indicate stable immobilization. Under the experimental conditions MB sorption was not significantly affected by pH, temperature and adsorbent concentration but low sorption was observed at higher NaCl concentrations.