• 한국세라믹학회지
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• 제29권2호
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• pp.89-94
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• 1992

The kinetics of volatilization of phosphorous oxide from phosphosilicate glassceramic powders prepared by a sol-gel process were investigated at a given temperature. The rate of P2O5 vaporization increased with the P2O5 concentration in the phosphosilicate powder. Vaporization from the powder containing 46% P2O5 was analyzed using a kinetic model for diffusion limited evaporation. The diffusion through phosphosilicate glass in the surface of each particle in the temperature range 800~85$0^{\circ}C$ are presented.

• 한국환경과학회지
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• 제27권2호
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• pp.83-90
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• 2018

In this study, zeolite (Z-C2) was synthesized using a fusion/hydrothermal method on coal fly ash (FA) discharged from a thermal power plant in the Ulsan area and then analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Z-C2 was characterized in terms of mineralogical composition and morphological analysis. The XRD results showed that its peaks had the characteristics of Na-A zeolite in the range of $2{\theta}$ of 7.18~34.18. The SEM images confirmed that the Na-A zeolite crystals had a chamfered-edge crystal structure almost identical to that of the commercial zeolite. The adsorption kinetics of Cu, Co, Mn and Zn ions by Z-C2 were described better by the pseudo-second-order kinetic model more than by the pseudo-first-order kinetic model. The Langmuir model fitted the adsorption isotherm data better than the Freundlich model did. The maximum adsorption capacities of Cu, Co, Mn and Zn ions obtained from the Langmuir model were in the following order : Cu (94.7 mg/g) > Co (77.7 mg/g) > Mn (57.6 mg/g) > Zn (51.1 mg/g). These adsorption capacities are regarded as excellent compared to those of commercial zeolite.

• The Korean Journal of Ceramics
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• 제2권4호
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• pp.181-183
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• 1996

We found that our initial model agrees with most of the recent reports; however, it does not agree with some of them with respect to the kinetics of nucleus formation. This disagreement stems from the question of whether or not a nucleus precursor should be treated as an embryonic cluster.

• Food Science and Biotechnology
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• 제15권5호
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• pp.664-671
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• 2006

Modeling the growth kinetics of lactic acid bacteria (LAB), one of the most valuable microbial groups in the food industry, has been actively pursued in order to understand, control, and optimize the relevant fermentation processes. Most modeling approaches have focused on the development of single population models. Primary single population models provide fundamental kinetic information on the proliferation of a primary LAB species, the effects of biological factors on cell inhibition, and the metabolic reactions associated with cell growth. Secondary single population models can evaluate the dependence of primary model parameters, such as the maximum specific growth rate of LAB, on the initial external environmental conditions. This review elucidates some of the most important single population models that are conveniently applicable to the LAB fermentation analyses. Also, a well-defined mixed population model is presented as a valuable tool for assessing potential microbial interactions during fermentation with multiple LAB species.

• Environmental Engineering Research
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• 제14권3호
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• pp.153-157
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• 2009

Arsenic at abandoned mine sites has adversely affected human health in Korea. In this study, the feasibility of using cationic surfactant-modified activated carbon (MAC) to remove As(V) was evaluated in terms of adsorption kinetics, adsorption isotherms, and column experiments. The adsorption of As(V) onto MAC was satisfactorily simulated by the pseudo-second-order kinetics model and Langmuir isotherm model. In column experiments, the breakthrough point of AC was 28 bed volumes (BV), while that of MAC increased to 300 BV. The modification of AC using cationic surfactant increased the sorption rate and sorption capacity with regard to As(V). As a result, MAC is a promising adsorbent for treating As(V) in aqueous streams.

• Environmental Engineering Research
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• 제16권2호
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• pp.55-60
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• 2011

The removal of hexavalent chromium from aqueous solutions onto modified holly sawdust was studied at varying initial hexavalent chromium concentrations, adsorbent doses, pHs and contact times. The removal of hexavalent chromium from aqueous solutions increased with increasing adsorbent dosage and contact time. The percentage of hexavalent chromium removed from the aqueous solutions decreased with increasing hexavalent chromium concentration and pH of the solution. The kinetics of the adsorption of hexavalent chromium onto modified holly sawdust was analyzed using pseudo first-order and pseudo second-order models. The pseudo second-order model described the kinetics of adsorption of hexavalent chromium. The Langmuir and Freundlich isotherm models were used for modeling of the adsorption equilibrium data. The Langmuir isotherm model well described the equilibrium data for the removal of hexavalent chromium by modified holly sawdust. The obtained maximum adsorption capacity was 18.86 mg/g at pH 7. The results showed that modified holly sawdust can be used as a low cost adsorbent for the treatment of aqueous solutions containing chromium.

• Environmental Engineering Research
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• 제25권2호
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• pp.205-211
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• 2020

Chlorhexidine digluconate (CHD) in the aquatic environment causes irreversible change to microbes, making them resistant to biodegradation, which needs remediation other than biological process. Adsorption study was performed for the removal of CHD on fly ash (FA) as a function of pH and ionic strength. Experimental result has been validated by characterization using Scanning electron microscopy, Fourier Transform-Infrared Spectroscopy and Brunauer-Emmett-Teller. CHD adsorption with FA showed an increasing trend with an increase in pH. Variation in pH proved to be an influential parameter for the surface charge of adsorbent and the degree of ionization of the CHD molecules. The adsorption capacity of CHD decreased from 23.60 mg g-1 to 1.13 mg g-1, when ionic strength increased from to M. The adsorption isotherms were simulated well by the Freundlich isotherm model having R2 = 0.98. The Lagergren's model was incorporated to predict the system kinetics, while the mechanistic study was better explained by pseudo-second order for FA. On the basis of operational conditions and cost-effectiveness FA was found to be more economical as an adsorbent for the adsorption of CHD.

• Journal of Microbiology and Biotechnology
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• 제17권7호
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• pp.1191-1197
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• 2007

The detection and kinetics of mucosal pathogenic bacteria binding on polysaccharide ligands were studied using a surface plasmon resonance biosensor. The kinetic model applied curve-fitting to the experimental surface plasmon resonance sensorgrams to evaluate the binding interactions. The kinetic parameters for the mucosal pathogenic bacteria (Pseudomonas aeruginosa, Pseudomonas fluorescens, Serratia marcescens) with the alginate ligand were determined from a kinetic model. In addition, the binding interactions of the mucosal pathogenic bacteria with polysaccharide binding pairs (Pseudomonas aeruginosa/alginate, Streptococcus pneumoniae/pneumococcal polysaccharide, Staphylococcus aureus/pectin) were also compared with their kinetic parameters. The rate constants of association for Pseudomonas aeruginosa with the alginate ligand were higher than those for Pseudomonas fluorescens. Serratia marcescens had no detectable interaction with the alginate ligand. The adhesion affinity of Pseudomonas aeruginosa with alginate was higher than that for the other binding pairs. The binding affinities of the pathogenic bacteria with their own polysaccharide were higher than that of Staphylococcus aureus with pectin. Measuring the contact angle was found to be a feasible method for detecting binding interactions between analytes and ligands.

• 한국표면공학회지
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• 제34권3호
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• pp.231-239
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• 2001

The structure and composition of Cr-nitrides formed on an electroplated hard Cr layer during an ionnitriding process was analyzed, and the growth kinetics of the Cr-nitrides was examined as a function of the ion-nitriding temperature and time in order to establish a computer simulation model prediction the growth behavior of the Cr-nitride layer. The Cr-nitrides formed during the ion-nitriding at $550~770^{\circ}C$ were composed of outer CrN and inner $Cr_2$N layers. A nitrogen diffusion model in the multi-layer based on fixed grid FDM (Finite Difference Method) was applied to simulate the growth kinetics of Cr-nitride layers. By measuring the thickness of each Cr-nitride layer as a function of the ion-nitriding temperature and time, the activation energy for growth of each Cr-nitride was determined; 82.26 KJ/mol for CrN and 83.36 Kj/mol for $Cr_2$N. Further, the nitrogen diffusion constant was determined in each layer; $9.70$\times$10^{-12}$ /$m^2$/s in CrN and $2.46$\times$10^{-12}$ $m^2$/s in $Cr_2$N. The simulation on the growth kinetics of Cr-nitride layers was in good agreements with the experimental results at 550~72$0^{\circ}C$.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.150-153
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• 2006

액체 로켓 엔진의 가스발생기는 터빈 블레이드의 열적 손상을 막기 위해 온도의 제한이 있으며 이를 위해 농후 또는 희박 연소를 하게 된다. 따라서 비평형 화학 반응이 주로 발생하며 이를 해석하는 것은 매우 어렵다. 본 연구에서는 케로신과 액체산소를 추진제로 하는 가스발생기에 대하여 Dagaut이 제안한 상세 화학 반응 단계를 사용하여 완전 혼합 반응기 연소 모델의 수정을 통해 계산하였으며, Frenklach의 soot 모델을 적용하여 예측 결과의 몰 분율, 가스 물성치 등의 결과에 대한 개선 방향을 제시하였다.