• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.137-145
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• 2009

The steady-state kinetics of the selective catalytic reduction (SCR) of $NO_X$ with $NH_3$ has been investigated over a commercial ${V_2}{O_5}/TiO_2$ catalyst. In order to account for the influence of transport effects the kinetics are coupled with a fully transient two-phase 1D+1D monolith channel model. The Langmuir-Hinshelwood (L-H) mechanism is adopted to describe the steady-state kinetic behavior of the ${V_2}{O_5}/TiO_2$ catalyst. The reaction rate expressions are based on previously reported papers and are modified to fit the experimental data. The steady-state chemical reaction scheme used in the present mathematical model has been validated extensively with experimental data of selective $NO_X$ reduction efficiency for a wide range of inlet conditions such as space velocity, oxygen concentrations, water concentration, and $NO_2/NO$ ratio. The parametric investigations are performed to examine how the $NH_3$ slip from a SCR $DeNO_X$ catalyst and the conversion of $NO_X$ are affected by the reaction temperature, $NH_3/NO_X$ feed ratio, and space velocity for feed gas compositions with $NO_2/NO_X$ ratios of 0 and 0.5.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.2
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• pp.27-34
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• 2014

Kinetic and isotherm properties of the cadmium adsorption onto calcium sand and granite soil were evaluated by batch experiments. The pHs of calcium sand and granite soil were 9.51 and 6.33, respectively, showing that the precipitation of heavy metals can be occurred due to the increase of pH when the calcium sand is used as an adsorbent. The pseudo-second-order model described the adsorption kinetics satisfactory with correlation coefficients over 0.999. The equilibrium adsorption capacities of calcium sand and granite soil were 2.10 and 2.16 mg/g, respectively. The adsorption isotherm followed the Freundlich isotherm model, indicating the cadmium adsorbed onto the heterogeneous surfaces of adsorbents.

• Journal of Environmental Science International
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• v.26 no.7
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• pp.859-868
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• 2017

In this study, the reductive dechlorination of triclosan using zero-valent iron (ZVI, $Fe^0$) and modified zero-valent iron (i.e., acid-washed iron (Aw/Fe) and palladium-coated iron (Pd/Fe)) was experimentally investigated, and the reduction characteristics were evaluated by analyzing the reaction kinetics. Triclosan could be reductively decomposed using zero-valent iron. The degradation rates of triclosan were about 50% and 67% when $Fe^0$ and Aw/Fe were used as reductants, respectively, after 8 h of reaction. For the Pd/Fe system, the degradation rate was about 57% after 1 h of reaction. Thus, Pd/Fe exhibited remarkable performance in the reductive degradation of triclosan. Several dechlorinated intermediates were predicted by GC-MS spectrum, and 2-phenoxyphenol was detected as the by-product of the decomposition reaction of triclosan, indicating that reductive dechlorination occurred continuously. As the reaction proceeded, the pH of the solution increased steadily; the pH increase for the Pd/Fe system was smaller than that for the $Fe^0$ and Aw/Fe system. Further, zero-order, first-order, and second-order kinetic models were used to analyze the reaction kinetics. The first-order kinetic model was found to be the best with good correlation for the $Fe^0$ and Aw/Fe system. However, for the Pd/Fe system, the experimental data were evaluated to be well fitted to the second-order kinetic model. The reaction rate constants (k) were in the order of Pd/Fe > Aw/Fe > $Fe^0$, with the rate constant of Pd/Fe being much higher than that of the other two reductants.

• Environmental Engineering Research
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• v.23 no.3
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• pp.330-338
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• 2018

This study investigated the possibility of using potassium titanate oxide ($K_2Ti_4O_9$) and acrylic acid-grafted polypropylene fabric (PP-g-AA) as adsorbents capable of removing strontium from aqueous solutions. $K_2Ti_4O_9$ showed the highest rate of strontium removal in the weak alkaline range, while the PP-g-AA increased strontium removal in the neutral range. Moreover, the adsorption capacity of the $K_2Ti_4O_9$ was not affected by the coexistence of K and Na ions, while the adsorption capacity decreased when Ca and Mg ions were present at the same concentration as that of strontium. When coexisted at the same concentration as strontium, Na, K, Ca, and Mg ions strongly reduced the adsorption capacity of the PP-g-AA. The results also indicated that the adsorption of strontium on $K_2Ti_4O_9$ was consistent with both the Langmuir and Freundlich adsorption isotherms. In contrast, the adsorption of strontium on the PP-g-AA was more consistent with the Langmuir isotherm model. Moreover, the adsorption equilibrium time of $K_2Ti_4O_9$ was generally 12 h, while that of the PP-g-AA was 5 h, indicating that the adsorption rates were consistent with the pseudo-second order kinetics model. $K_2Ti_4O_9$ and the PP-g-AA could be regenerated by simple washing with 0.5 N HCl.

• Microbiology and Biotechnology Letters
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• v.16 no.4
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• pp.282-286
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• 1988

Growth kinetic parameters for mass cultivation of Chinese Hamster Ovary (CHO) cells are estimated by measuring oxygen uptake rates. It Is found that there is strong correlation between cell growth and oxygen consumption, showing that correlation factor is 0.83. Derived linear model predicts actual cell density very well. It tells that oxygen uptake rate can play important role in indirectly measuring cell density when conventional method of estimating cell density is no longer meaningful due to heavy cell clumpings. Cell yield per oxygen consumption, $Y_{\chi}o$ and mass transfer coefficient for oxygen, Ka are also estimated as 1.26$\times$10$^4$cells/mmole $O_2$ consumed and 1.01/h, respectively. Average specific growth rate over all runs is 2.891/day for CHO cells with producting 2 grams of tPA per day under continuous perfusion operations.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.199-204
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• 2016

The adsorption of Rhodamine-B dye using granular activated carbon from aqueous solution was investigated. Adsorption experiments were carried out as a function of the adsorbent dose, pH initial concentration, contact time and temperature. The equilibrium adsorption data showed a good fit to Langmuir isotherm model. Based on the estimated Langmuir separation factor ($R_L$ = 0.0164~0.0314), our adsorption process could be employed as an effective treatment method. The kinetics of adsorption followed the pseudo first order model. Also, the negative values of Gibbs free energy (-4.51~-13.44 kJ/mol) and positive enthalpy (128.97 kJ/mol) indicated that the adsorption was spontaneous and endothermic process. The isosteric heat of adsorption increased with increase in the surface loading indicating lateral interactions between the adsorbed dye molecules.

• Food Science and Biotechnology
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• v.17 no.6
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• pp.1316-1321
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• 2008

This study was conducted to develop a model to describe the effect of antimicrobials [potassium sorbate (PS), potassium lactate (PL), and combined PL and sodium diacetate (SDA, PLSDA)] on the growth parameters of Listeria monocytogenes such as specific growth rate (SGR) and lag phase periods (LT) in air-dried raw sausages as a function of storage temperature (4, 10, 16, and $25^{\circ}C$). Results showed that the SGR of L monocytogenes was dependent on the storage temperature and level of antimicrobials used. The most effective treatment was the 4% PLSDA, followed by the 2% PLSDA and 4% PL and 0.2% PS exhibited the least antimicrobial effect. Increased growth rates were observed with increasing storage temperatures from 4 to $25^{\circ}C$. The growth data were fitted with a Gompertz equation to determine the SGR and LT of the L. monocytogenes. Six polynomial models were developed for the SGR and LT to evaluate the effect of PS (0.1, 0.2%) and PL (2,4%) alone and PLSDA (2, 4%) on the growth kinetics of L. monocytogenes from 4 to $25^{\circ}C$.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.493-502
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• 2021

We prepared and investigated a biosynthesized nanoparticulate system with high adsorption and release capacity of letrozole. Silver nanoparticles (AgNPs) were biosynthesized using olive leaf extract. Cysteine was capped AgNPs to increase the adsorption capacity and suitable interaction between nanoparticles and drug. Morphology and size of nanoparticles were confirmed using transmission electron microscopy (TEM). Nanoparticles were spherical with an average diameter of less than 100 nm. Cysteine capping was successfully confirmed by Fourier transform infrared resonance (FTIR) spectroscopy and elemental analysis (CHN). Also, the factors of letrozole adsorption were optimized and the linear and non-linear forms of isotherms and kinetics were studied. Confirmation of the adsorption data of letrozole by cysteine capped nanoparticles in the Langmuir isotherm model indicated the homogeneous binding site of modified nanoparticles surface. Furthermore, the adsorption rate was kinetically adjusted to the pseudo-second-order model, and a high adsorption rate was observed, indicating that cysteine coated nanoparticles are a promising adsorbent for letrozole delivery. Finally, the kinetic release profile of letrozole loaded modified nanoparticles in simulated gastric and intestinal buffers was studied. Nearly 40% of letrozole was released in simulated gastric fluid with pH 1.2, in 30 min and the rest of it (60%) was released in simulated intestinal fluid with pH 7.4 in 10 h. These results indicate the efficiency of the cysteine capped AgNPs for adsorption and release of drug letrozole for breast cancer therapy.

• Korean Journal of Materials Research
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• v.29 no.7
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• pp.412-424
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• 2019

Global fitting functions for Fe-selective chlorination in ilmenite($FeTiO_2$) and successive chlorination of beneficiated $TiO_2$ are proposed and validated based on a comparison with experimental data collected from the literature. The Fe-selective chlorination reaction is expressed by the unreacted shrinking core model, which covers the diffusion-controlling step of chlorinated Fe gas that escapes through porous materials of beneficiated $TiO_2$ formed by Fe-selective chlorination, and the chemical reaction-controlling step of the surface reaction of unreacted solid ilmenite. The fitting function is applied for both chemical controlling steps of the unreacted shrinking core model. The validation shows that our fitting function is quite effective to fit with experimental data by minimum and maximum values of determination coefficients of $R^2$ as low as 0.9698 and 0.9988, respectively, for operating parameters such as temperature, $Cl_2$ pressure, carbon ratio and particle size that change comprehensively. The global fitting functions proposed in this study are expressed simply as exponential functions of chlorination rate(X) vs. time(t), and each of them are validated by a single equation for various reaction conditions. There is therefore a certain practical merit for the optimal process design and performance analysis for field engineers of chlorination reactions of ilmenite and $TiO_2$.

• Korean Journal of Environmental Agriculture
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• v.40 no.4
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• pp.239-247
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• 2021

BACKGROUND: Enormous amounts of the wood biomass wastes have been produced through various wood processing. This study characterizes the surface characteristics of biomass powders of Cornus controversa (CC) and Quercus mongolica (QM) and investigates their removal efficiency and mechanism for Pb (II) in aqueous solution on which to base potential recycling alternative of the wood biomass. METHODS AND RESULTS: Batch experiments were conducted under different conditions of Pb concentrations, temperatures, time and solid/solution ratios. Adsorption isotherm of Pb by CC and QM biomass was explained significantly by the Langmuir model, indicating Pb was likely adsorbed on the monolayer of the surfaces. The adsorption kinetics were fitted significantly to the double first-order model consisting of rapid and slow steps. The respective rate constants (k1) of CC and QM for the rapid adsorption kinetic steps were 0.051 and 0.177 min^-1, and most of the sorption reactions proceeded rapidly within 6-20 minutes. The maximum adsorption quantities (q_max) of Pb were 17.25 and 23.47 mg/g for CC and QM, respectively. Thermodynamic parameters revealed that adsorption of Pb on the biomass of CC and QM was a spontaneous endothermic reaction. CONCLUSION(S): Results demonstrate that biomass wastes of CC and QM can be used as Pb adsorbents judging from adsorption isotherm, kinetics, and thermodynamic parameters.