• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1113-1118
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• 2008

Characteristics of reduction properties and carbon deposition of $CuFe_2O_4$ and $Fe_3O_4$ were investigated by using TGA, XRD, SEM, TEM and gas analysis at $900^{\circ}C$. XRD analyses indicated that the reduced $Fe_3O_4$ was composed of Fe, graphite and $Fe_3C$ phases. In contrast, the reduced $CuFe_2O_4$ did not show the graphite or $Fe_3C$ phases. It was observed by SEM analysis that the surface of the $Fe_3O_4$ was completely covered with carbon, after methane partial oxidation. From gas analysis, $CuFe_2O_4$ showed much higher methane conversion and reduction kinetics as compared to the $Fe_3O_4$ under the same reaction conditions and the estimated carbon deposition amounts on the reduced $CuFe_2O_4$ was much lower than those on the reduced $Fe_3O_4$ during the syngas production process. It was found by TEM that carbon on the reduced $Fe_3O_4$ particles has a platelet shape.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1101-1109
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• 2010

We investigated the combustion rate and kinetic rate of char when burning in oxygen-enriched atmospheres with either an $N_2$ or $CO_2$ bath gas in a drop tube furnace. The experiments were performed with sub-bituminous coal (Adaro) and bituminous coal (Coal valley) under atmospheric pressure conditions. Two different coals were investigated over 12 to 30 vol% oxygen and furnace temperatures of 900, 1100, and $1300^{\circ}C$. For both coals, the particle temperature and overall reaction rate are lower in the $CO_2$ bath gas. However, analysis of single-particle data shows that the surface-specific burning rate of char oxidation is similar in both gases. In addition, the kinetic rate and activation energy for each coal were similar for both gases. Generally, the particle temperature and overall reaction rate of sub-bituminous coal are higher than those of bituminous coal.

• Resources Recycling
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• v.30 no.4
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• pp.11-19
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• 2021

Arsenic (As) oxidation followed by precipitation from a high-As(III)-containing leaching solution derived from a sulfidic ore was investigated in this study to remove aqueous As from the solution using activated carbon (AC) with air injection as an oxidant. To obtain the initial leaching solution, a domestic sulfidic ore was leached in a sulfuric acid solution at pH 1 and 50℃ for 95 h, and approximately 7 g/L of Fe and 3 g/L of As were leached out. To determine the effect of the oxidative reaction utilizing AC with air injection, the leaching solution was tested under the following five oxidative conditions at an initial pH of 1 and 90℃ for 72 h: air-only injection; air injection with 1, 5, and 10 w/v% of AC addition; and H₂O₂ addition. The tests in the presence of both air and AC revealed that the oxidation kinetics and As removal were improved by the reaction between the metallic species and the surface group formed on the AC surface. In addition, the greater the amount of AC added, the better was the reaction efficiency, removing 93-94% of As with more than 5 w/v% of AC addition. Finally, X-ray diffraction analysis confirmed that the precipitate formed from the oxidative reaction was scorodite (FeAsO₄·2H₂O).

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.259-267
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• 2010

The catalytic wet oxidations of the wastewater containing azo dye Reactive Black 5(RB5) with heterogeneous catalyst of CuO have been carried out to investigate the effects of temperature($190{\sim}230^{\circ}C$) and catalyst concentration(0.00~0.20 g/l) on the removals of colour and total organic carbon TOC. The wastewater colour was measured with spectrophotometer, and the oxidation rate was estimated with TOC. About 90% of colour was removed during 120 min in thermal degradation of the RB5 wastewater at $230^{\circ}C$, while TOC was not removed at all. As increasing reaction temperature and catalyst concentration, the removal rates of colour and TOC increased in the catalytic wet oxidations of RB5 wastewater. The effects of catalyst were already considerable even at 0.01 g CuO/l, while the removal rates of colour and TOC increased negligibly with increasing the catalyst concentration above 0.05 g CuO/l. The initial destruction rates of the wastewater colour have shown the first-order kinetics with respect to the wastewater colour. TOC changes during catalytic wet oxidations have been well described with the global model, in which the easily degradable TOC was distinguished from non-degradable TOC of the wastewater. The impacts of reaction temperature on the destruction rate of the wastewater colour and TOC could be described with Arrhenius relationship. Activation energies of the colour removal reaction in thermal degradation, wet oxidation, and catalytic wet oxidation(0.20 g CuO/l) of the RB5 wastewater were 108.4, 78.3 and 74.1 kJ/mol, respectively. The selectivity of wastewater TOC into the non-degradable intermediates relative to the end products in the catalytic wet oxidations of RB5 wastewater was higher compared to that in phenol wet oxidations.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.602-609
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• 1997

The seed formation and growth of $\alpha$-ferric oxyhydroxide with aerial oxidative precipitation from aqueous solution of ferrous sulfate with KOH, NaOH, $Na_2CO_3$ and $K_2CO_3$ as precipitants have been studied by free pH drift experiment. It has been shown that all precipitants give same particle formation and growth path, and average particle length from KOH and NaOH as precipitants was about 1.5 times shorter than that of $K_2CO_3$ and $Na_2CO_3$. When initial mole ratio, $R_o=[Fe^{2+}]_o/[OH^-]_o$ of KOH was decreased the particle was grown oxyhydroxide seed growth from aqueous solution of ferrous sulfate with KOH has been studied. The influence of the air flow rate, reaction temperature and initial mole ratio, $R_o=[Fe^{2+}]_o/[OH^-]_o$, on the kinetics of seed growth are investigated by static pH experiment. The oxidation rate of seed growth increased with increase in the air low rate, reaction temperature and initial mole patio. The activation energy of seed growth is 16.16 KJ/mol and the rate equation of seed growth can be written as follows: $-\frac{d[Fe^{2+}]}{dt}=1.46{\times}10^4[P_{o2}]^{0.66}[OH^-]^{2.19}exp(-\frac{16.16}{dt})$.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1869-1879
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• 2000

A series of experiments were conducted for modeling the fate and effect of the coupled oxidation reduction reaction of ethanol and propionate recognized as important intermediates in anaerobic degradation metabolism. Anaerobic kinetics for conversion of propionate and the interaction with ethanol were investigated using the model of specific substrate priority utilization effect. Seed cultures for the experiment were obtained from an anaerobically enriched steady-state propionate master culture reactor (HPr-MCR), ethanol-propionate master culture reactor (EtPr-MCR) and glucose master culture reactor (Glu-MCR). Experiments were consisted of four phases. Phase I, II and III were conducted by fixing the propionate organic loading as 1.0 g COD/L with increasing ethanol loading of 0, 100, 200, 400 and 1,000 mg/L, to find metabolic interaction of ethanol and propionate degradation by each enriched anaerobic culture. In phase IV, different mixing ratios of Glu-MCR and HPr-MCR cultures with fixed propionate organic loading, 1.0 g COD/L, were applied to observe the propionate degradation metabolic behavior. In the results of this study, different pathways of propionate and ethanol conversion were found using a modified competitive inhibition kinetic model. Increase of $K_{s2}$ value reflected the formation of acetate followed by ethanol degradation. In addition. $K_3$ value was increased slightly as the reactions of acetate formation and degradation were occurred in acetoclastic methanogenesis.

• Polymer(Korea)
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• v.36 no.6
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• pp.712-720
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• 2012

Thermal degradation for glass fiber-reinforced polyamide 66 composite (PA 66) with respect of thermal exposure time has been investigated using optical microscopy, scanning electron microscopy and Fourier transform infrared spectroscopy. As the thermal exposure time was prolonged, a slight increase in tensile strength for only initial stage and afterward, a proportional decrease of tensile strength was observed. These results can be explained by the increase of crystallinity, followed by the increase of crosslinking density, chain scission and the decrease in chain mobility, due to thermal oxidation with the exposure time. Fourier transform infrared spectroscopy results showed the increase of ketone peak and silica peak on the surface of thermally exposed PA 66. In addition, the thermal decomposition kinetics of PA 66 was analyzed using thermogravimetric analysis at three different heating rates. The relationship between activation energy and lifetime-prediction of PA 66 was investigated by several methodologies, such as statistical tool, UL 746B, Ozawa and Kissinger. The activation energy determined by thermogravimetric analysis had a relatively large value compared with that from the accelerated test. This may result in over-estimating the lifetime of PA 66. In this study, a master curve of exponential fitting has been developed to extrapolate the activation energy at various service temperatures.

• Journal of the Korean Society of Combustion
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• v.18 no.4
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• pp.37-43
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• 2013

The effects of preferential diffusion of hydrogen in interacting counterflow $H_2$-air and CO-air premixed flames were investigated numerically. The global strain rate was varied in the range $30-5917s^{-1}$, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures for a mixed average diffusivity with those where the diffusivities of H, $H_2$ and $N_2$ were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of $H_2$ and CO as a function of the strain rate. The main oxidation route for CO is $CO+O_2{\rightarrow}CO_2+O$, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely $CO+OH{\rightarrow}CO_2+H$, can be significant, provided that hydrogen from the $H_2$-air flame is penetrated and then participates in the CO-oxidation. This modifies the flame characteristics in the downstream interaction between the $H_2$-air and CO-air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to depend on chemical interaction between the two flames. Such anomalous behaviors include a partial opening of the upper lean extinction boundary in the interaction between a lean $H_2$-air flame and a lean CO-air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich $H_2$-air flame and a lean CO-air flame. At large strain rates, there are two islands where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.6000-6007
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• 2013

Cr(VI)-heterocyclic complex[Cr(VI)-isoquinoline] was synthesized by the reaction between of heterocyclic compound(isoquinoline) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using Cr(VI)-isoquinoline in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order : cyclohexene$CH_3$, m-Br, m-$NO_2$). Electron- donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.69(308K). The observed experimental data have been ratiolized. The hydride ion transfer causes the prior formation of a chromate ester in the rate-determining step.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.597-600
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• 2017

$(C_{10}H_8N_2H)_2Cr_2O_7$ was synthesized by reacting 4,4'-bipyridine and chromium (VI) trioxide. The structure of the product was characterized with FT-IR (infrared spectroscopy) and elemental analysis. The oxidation of benzyl alcohol using $(C_{10}H_8N_2H)_2Cr_2O_7$ in various solvents showed that the reactivity increased with the increase of the solvent dielectric constant, in the order of DMF (N,N'-dimethylformamide) > acetone > chloroform > cyclohexane. In the presence of DMF, an acidic catalyst such as $H_2SO_4$ $(C_{10}H_8N_2H)_2Cr_2O_7$ oxidized benzyl alcohol (H) and its derivatives ($p-OCH_3$, $m-CH_3$, $m-OCH_3$, m-Cl, $m-NO_2$). Electron donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. Hammett reaction constant (${\rho}$) was -0.70 (308 K). The observed experimental data were used to rationalize the hydride ion transfer in the rate determining step.