• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.210-218
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• 2019

Batch experiment studies were carried out on the adsorption of the major tar compound, 2-picoline, derived from the plant cell cultures of Taxus chinensis, using Sylopute while varying parameters such as initial 2-picoline concentration, contact time and adsorption temperature. The experimental data were fitted to the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. Comparison of results revealed that the Langmuir isotherm model could account for the adsorption isotherm data with the highest accuracy among the four isotherm models considered. From the analysis of adsorption isotherms, it was found that adsorption capacity decreased with increasing temperature and the adsorption of 2-picoline onto Sylopute was favorable. The kinetic data were well described by the pseudo-second-order kinetic model, while intraparticle diffusion and boundary layer diffusion did not play a dominated role in 2-picoline adsorption according to the intraparticle diffusion model. Thermodynamic parameters revealed the exothermic, irreversible and non-spontaneous nature of adsorption. The isosteric heat of adsorption decreased as surface loading ($q_e$) increased, indicating a heterogeneous surface.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.106-112
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• 2007

Ammonia oxidizing bacteria(AOB) oxidize ammonia to nitrite and are important microorganisms which control nitrification. Several environmental factors such as dissolved oxygen(DO), temperature and pH influence the growth of AOB. In this work, to assess the effect of DO concentration on AOB, four aerobic biofilm reactors packed with ceramic media were operated 1, 3, 5 and 7 mgDO/L, respectively. The optimal DO concentration with stable nitrification efficiency in aerobic biofilm reactor was above 5.0 mg/L. To assess the relationship between the DO concentration and the characteristics of AOB in aerobic biofiim reactor, DGGE and cloning based on PCR targeting 16S rRNA and amoA gene were performed. Additionally, INT-DHA activity test was proceeded to estimate the activity of AOB. As the results of DGCE and cloning, the community of AOB and the ratio of Nitrosomonas sp. changed little in spite of different nitrification efficiencies. INT-DHA activity test showed that the activity of AOB decreased as DO concentration decreased. It means that DO concentration does not affect the community of AOB, but the activity of AOB.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.746-752
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• 2005

In this study, the effect of reaction parameters including reaction temperature, time, and pressure on sludge degradation and conversion to intermediates such as organic acids were investigated at low critical wet air oxidation(LC-WAO) conditions. Degradation pathways and a modified kinetic model in LC-WAO were proposed and the kinetics model predictions were compared with experimental data under various conditions. Results in the batch experiments showed that reaction temperature directly affected the thermal hydrolysis reaction rather than oxidation reaction. The efficiencies of sludge degradation and organic acid formation increased with the increase of the reaction temperature and time. The removal of SS at $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ and $240^{\circ}C$ of reaction temperatures and 10 min of reaction time were 52.6%, 68.3%, 72.6%, and 74.4%, respectively, indicating that most organic suspended solids were liquified at early stage of reaction. At $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ and $240^{\circ}C$ of reaction temperatures and 40 min of reaction time, the amounts of organic acids formed from 1 g of sludge were 93.5 mg/g SS, 116.4 mg/g SS, 113.6 mg/g SS, and 123.8 mg/g SS, respectively, and the amounts of acetic acid from 1 g of sludge were 24.5 mg/g SS, 65.5 mg/g SS, 88.1 mg/g SS, and 121.5 mg/g SS, respectively. This suggested that the formation of sludge to organic acids as well as the conversion of organic acids to acetic acid increased with reaction temperature. Based on the experimental results, a modified kinetic model was suggested for the liquefaction reaction of sludge and the formation of organic acids. The kinetic model predicted an increase in kinetic parameters $k_1$ (liquefaction of organic compounds), $k_2$ (formation of organic acids to intermediate), $k_3$ (final degradation of intermediate), and $k_4$ (final degradation of organic acids) with reaction temperature. This indicated that the liquefaction of organic solid materials and the formation of organic acids increase according to reaction temperature. The calculated activation energy for reaction kinetic constants were 20.7 kJ/mol, 12.3 kJ/mol, 28.4 kJ/mol, and 54.4 kJ/mol, respectively, leading to a conclusion that not thermal hydrolysis but oxidation reaction is the rate-limiting step.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.279-290
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• 2016

The performance of upflow anaerobic bioelectrochemical reactor (UABE), equipped with electrodes (anode and cathode) inside the upflow anaerobic reactor, was compared to that of upflow anaerobic sludge blanket (UASB) reactor for the treatment of acidic distillery wastewater. The UASB was stable in pH, alkalinity and VFAs until the organic loading rate (OLR) of 4.0 g COD/L.d, but it became unstable over 4.0 g COD/L.d. As a response to the abrupt doubling in OLR, the perturbation in the state variables for the UABE was smaller, compared to the UASB, and quickly recovered. The UABE stability was better than the UASB at higher OLR of 4.0-8.0 g COD/L.d, and the UABE showed better performance in specific methane production rate (2,076mL $CH_4/L.d$), methane content in biogas (66.8%), and COD removal efficiency (82.3%) at 8.0 g COD/L.d than the UASB. The maximum methane yield in UABE was about 407mL/g $COD_r$ at 4.0 g COD/L.d, which was considerably higher than about $282mL/g\;COD_r$ in UASB. The rate limiting step for the bioelectrochemical reaction in UABE was the oxidation of organic matter on the anode surface, and the electrode reactions were considerably affected by the pH at 8.0 g COD/L.d of high OLR. The maximum energy efficiency of UABE was 99.5%, at 4.0 g COD/L.d of OLR. The UABE can be an advanced high rate anaerobic process for the treatment of acidic distillery wastewater.

• Journal of Soil and Groundwater Environment
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• v.6 no.2
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• pp.39-47
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• 2001

According to a series of batch-scale washing tests, SDS+$POE_5$ and $POE_5$+$POE_14$ were determined for the applicable mixed surfactants. Because SDS+$POE_5$ showed slightly negative effects on the microbes in the toxicity tests, $POE_5$+$POE_14$((1:1) 1%) was chosen for this study. In the in-situ flushing experiments, the removal rate of endosulfan was 67% for the injection rate of 1.5L/min/$\textrm{km}^2$. And when methanol and ethanol were added as cosolvent, 75% and 81% removal efficiencies were achieved, respectively. In the tests of bioremediation after the application of in-situ flushing, the removal rates of contaminated soils having 13mg/kg dry soil and 3mg/kg dry soil as initial concentrations were 86% and 81%, respectively. There were no significant degradation after 24 hours. The major rate-limiting factor for the biodegradation of endosulfan might be the mass transfer from soil phase to liquid phase after 24 hours. With the addition of surfactant, 89% removal was achieved after 120 hours. Because the surfactant improved the mass transfer rate, the biodegradation of endosulfan was enhanced. When surfactant and cosolvent were added together, the adaptation period of microorganisms to the surfactant became longer and the removal rates were 84% and 83% for methanol and ethanol, respectively.

• Korean Journal of Materials Research
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• v.4 no.3
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• pp.301-311
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• 1994

The growth of amorphous and first crystalline phase, and phase sequence by solid state reaction were examined in Co/Si multilayer thin films by DSC and XRD. The experimental results were compared with the results expected by effective driving force models, PDF and effective heat of formation models.Amorphous phase growth was not observed in Co/Si system and it was consistent with the predicted result by effective driving force. It was observed that the first crystalline phase is CoSi. According to the PDF and effective heat of formation models, the first crystalline phases were CoSi and $CO_2Si$, respectively. The experiemental results were coincident with the PDF model considering structure factors. In case of the atomic concentration ratios of 2Co : 1Si and 1Co : 2Si, the phases sequences were $CoSi\to Co_2Si$ and $CoSi \to Co_2Si \to CoSi \to CoSi_2$, respectively and it was analysized through the effective heat of formation model. The formations of CoSi, $CO_2Si$ and $COSi_2$ in initial stage were controlled by nucleation and the activation energies for the nucleation of three phases were 1.71, 2.34 and 2.79eV.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.293-298
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• 1999

Reaction mechanism was elucidated and reaction condition were optimized for the catalytic reaction synthesizing 2-methyl-4-methoxy-diphenylamine (MMDPA) which is an intermediate of Fluoran heat-sensitive dyestuff. Reactants consisted of 2-methyl-4-methoxyaniline (MMA), 3-methyl-4-nitroanisole (MNA), and cyclohexanone, and 5 wt % Pd/C was used as a catalyst. Experiments were run in an open slurry reactor equipped with reflux condenser, and products were analyzed by means of GC/MS and NMR. MMDPA yield of 90 mole % could be obtained after reaction time of 8~10 hours under the optimal reaction conditions comprising the reaction mass composition of MMA : MNA : cyclohexanone = 1 : 2 : 150 based on MMA input of 0.01 gmoles in xylene solvent, reaction temperature of $160^{\circ}C$, and catalyst amount of 0.5 g. It was found that the rate-determining step of overall reaction was dehydrogenation of the intermediate product obtained from condensation of MMA and cyclohexanone. Overall reaction rate and MMDPA yield were enhanced owing to hydrogen transfer reaction by introducing MNA together with MMA in the reaction mass. Excess cyclohexanone in the reaction mass played an important role of promoting the condensation of MMA and cyclohexanone.

• Journal of the Korean Chemical Society
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• v.44 no.5
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• pp.453-459
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• 2000

FED has deserved an intensive attentioD as a new flat panel display. The present investigationaims at undemtanding the photoluminescence and cathodoluminescent properties of hGaO$_3$: $Eu^{3+}$ phosphor bytaking into account the possibility that this phosphor could be applied for FED. In onler to investigate on.sucha detailed behavior; 8everM experimental skil18 Je conducted to the LaGaO$_3$:$Eu^{3+}$ phosphoL The excimtion srectrum artd emission spectmn were rnezsured in the UV range and then decay curve of $^5D_0$+$^7F_j$transitions\vas examined. The decay behavior of $^5D_0$ emission was anMyzed by a newly Iuoposed cross-relaxation mech-ani8In in asswiation with inteFwnter di1ffision (or migration). The cross-mlaxation from $^5D_0$ to CTB (Cha'geTransfer Band) wuld be a quite retsonable by considering the excitation spectrum. It could be also found thatthe quenching type was changed from ditfrsion controlled process to the direct quenching process -s inJeasing $Eu^{3+}$ oncntration.

• Nuclear Engineering and Technology
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• v.17 no.3
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• pp.211-215
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• 1985

The effects of temperature and strain rate on the I-SCC behaviors of Zircaloy-4 were investigated by constant load test at 30$0^{\circ}C$ and constant elongation rate test at 300, 350 and 40$0^{\circ}C$ in 3.34mg $I_2$/㎤. The results showed that I-SCC susceptibility increased as the strain rate decreased or the temperature increased. The empirical relation between the stress and the time to failure at 30$0^{\circ}C$ was given by 1/ $t_{f}$∝exp (0.3$\sigma$/$\sigma$$_{UTS}$-31.5) When the I-SCC susceptibility was expressed by the ratio of fracture energy in iodine atmosphere to that in the inert atmosphere, severe I-SCC susceptibility was found near 7.6$\times$10$^{-6}$ sec at 30$0^{\circ}C$ and the maximum point of I-SCC susceptibility tended to shift to the higher strain rate with increasing the temperature. The quasi-cleavage fracture was observed in I-SCC fracture surface. From these results, it was certain that the film repture step was involved as an important process in the I-SCC mechanism of Zircaloy-4.4.