• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.703-709
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• 2013

Ozonation was performed under various experimental conditions that $Al_2O_3$ catalysts dosage and temperature for removal of DMP in laboratory scale batch reactor. Flow rate of ozone $1.0Lmin^{-1}$ and ozone concentration of $300{\pm}10mgL^{-1}$ were maintained constantly, and the pH, $COD_{Cr}$ and TOC was measured in 10 min intervals during the 60 min at oxidation processes. As a result, the presence of the $Al_2O_3$ than only ozonation increased the removal efficiency of both $COD_{Cr}$ and TOC in solution. The pseudo first-order rate constants for the elimination of $COD_{Cr}$ and TOC were $3.65{\times}10^{-4}sec^{-1}$, $2.52{\times}10^{-4}sec^{-1}$, and activation energy was $0.75kcal{\cdot}mol^{-1}$ and $0.70kcal{\cdot}mol^{-1}$ at $20^{\circ}C$, respectively.

• Journal of Power System Engineering
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• v.20 no.4
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• pp.69-74
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• 2016

Recently, in order to meet the stricter emission regulations, the proportion of after-treatments for vehicle and vessel is increasing gradually. The purpose of this study is to investigate the de-$CH_4$ characteristics of NGOC in front of proposed combined system according to additive catalyst and support ratio. In the case of Pd addition, the de-$CH_4$ performance of 2Pt-2Pd-3MgO/$Al_2O_3$ NGOC was improved by approximately 10 to 20% for the HC components. The de-$CH_4$ performance of 2Pt-2Pd-3Cr-3MgO/$Al_2O_3$ NGOC was higher compared to five kinds of NGOC catalysts, because Cr particle was smaller and dispersion of Pd was increased. The NGOC(Zeolite:$Al_2O_3$(80%:20%)｝catalyst according to support ratio, was improved performance at low temperature region on CO and NO conversion rate.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2207-2219
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• 2018

Activated carbon (AC) was synthesized from Phoenix dactylifera stones and then modified by $CoFe_2O_4$ magnetic nanocomposite for use as a Cr(VI) adsorbent. Both $AC/CoFe_2O_4$ composite and AC were fully characterized by FTIR, SEM, XRD, TEM, TGA, and VSM techniques. Based on the surface analyses, the addition of $CoFe_2O_4$ nanoparticles had a significant effect on the thermal stability and crystalline structure of AC. Factors affecting chromium removal efficiency like pH, dosage, contact time, temperature, and initial Cr(VI) concentration were investigated. The best pH was found 2 and 3 for Cr adsorption by AC and $AC/CoFe_2O_4$ composite, respectively. The presence of ion sulfate had a greater effect on the chromium sorption efficiency than nitrate and chlorine ions. The results illustrated that both adsorbents can be used up to seven times to adsorb chromium. The adsorption process was examined by three isothermal models, and Freundlich was chosen as the best one. The experimental data were well fitted by pseudo-second-order kinetic model. The half-life ($t_{1/2}$) of hexavalent chromium using AC and $AC/CoFe_2O_4$ magnetic composite was obtained as 5.18 min and 1.52 min, respectively. Cr(VI) adsorption by AC and $AC/CoFe_2O_4$ magnetic composite was spontaneous and exothermic. In general, our study showed that the composition of $CoFe_2O_4$ magnetic nanoparticles with AC can increase the adsorption capacity of AC from 36 mg/L to 70 mg/L.

• Journal of the Korean earth science society
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• v.32 no.7
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• pp.707-718
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• 2011

We study the natural background and geochemical characteristics on geological groups of stream sediment in the Boseong-Hwasun area. We collected 186ea stream sediment samples along the primary channels and dried them naturally in laboratory. The contents of major, trace and rare earth elements were determined by XRF, ICP-AES and NAA analysis methods. In order to know the natural background and geochemical characteristics of geological groups, we classified the studied area into granitic gneiss (GGn) area and porphyroblastic gneiss (PGn) area. The contents range of major elements for GGn area is $SiO_2$ 45.5-73.09 wt.%, $Al_2O_3$ 12-20.76 wt.%, $Fe_2O_3$(T) 3.72-8.85 wt.%, $K_2O$ 2.38-4.2 wt.%, MgO 0.75-2.77 wt.%, $Na_2O$ 0.78-1.88 wt.%, CaO 0.27-2.1 wt.%, $TiO_2$ 0.56-1.72 wt.%, $P_2O_5$ 0.06-0.73 wt.% and MnO 0.03-0.95 wt.%, and for PGn area it is $SiO_2$ 43.74-70.71 wt.%, $Al_2O_3$ 11.54-25.05 wt.%, $Fe_2O_3$(T) 3.44-13.46 wt.%, $K_2O$ 2.08-3.86 wt.%, MgO 0.65-2.99 wt.%, $Na_2O$ 0.63-1.7 wt.%, CaO 0.35-2.07 wt.%, $TiO_2$ 0.68-4.17 wt.%, $P_2O_5$ 0.1-0.31 wt.% and MnO 0.07-0.33 wt.%. The contents range of hazard elements for GGn area is Cr 41.7-242 ppm, Co 7.6-25.1 ppm, Ni 12-61 ppm, Cu 10-47 ppm, Zn 48.5-412 ppm, Pb 17-215 ppm, and for PGn area, it is Cr 29.6-454 ppm, Co 5.9-53.7 ppm, Ni 8.7-287 ppm, Cu 6.4-134 ppm, Zn 43.6-370 ppm, Pb 15-37 ppm area. There is a good correlation between Cr and MgO and Co among $Al_2O_3$, $Fe_2O_3$(T), MgO and Ni among $Fe_2O_3$(T), CaO, MgO whereas Cu, Zn and Pb have a low correlation for major elements in GGn area. Generally Cr, Co, Ni, and Cu have a good correlation with major elements, but a low correlation with Zn and Pb in PGn area.

• Applied Chemistry for Engineering
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• v.2 no.3
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• pp.279-288
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• 1991

Mg- and Zn-ferrites having spinel structure, a kind of complex oxides showing the advantageous properties of constituent single metal oxides, were selected to find a relationship between their catalytic activities in the dehydrogenation of ethylbenzene to styrene and the catalytic properties. For the structural and physical analyses of ferrites, XRD, BET, TG/DTA, ESCA, TEM, and TPD methods were employed. The effects of Cr-substitution were intensively studied by the experimental methods mentioned above. Chromium which showed a preferential tendency to diffuse to the surface acted as a structural promoter by increasing surface area and stability of catalyst structure. In the dehydrogenation of ethylbenzene, catalytic activity, and the effects of Cr-substitution were investigated. Oxygen mobility was decreased with the amount of Cr-substitution in $MgCr_xFe_{2-x}O_4$, which resulted in the increase of selectivity to styrene and the suppression of total oxidation.

• Journal of Environmental Health Sciences
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• v.19 no.3
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• pp.29-35
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• 1993

This study was performed to obtain optimal conditions for reduction of color in dye wastewaters using coagulation-sedimentation processes with redox reactions. The reduction of color as well as organic matters variation was observed after coagulation-sedimentation processes using FeSO$_4$ $\cdot$ 7H$_2$O and NaOCl. Coagulation-redox reaction was done with the dose of Coagulant and oxidant at various pH values. Redox reaction was done through jar-mixing and aeration. The results of study were as follows: 1. In the coagulation-sedimentation processes using FeSO$_4$ $\cdot$ 7H$_2$O, color reduction was heigher at pH 3. With variance of dosage of FeSO$_4$ $\cdot$ 7H$_2$O, color reduction was higher at 250 mg/l. When coagulation-sedimentation using FeSO$_4$ $\cdot$ 7H$_2$O 250 mg/l was added at pH 3, the reduction of color, COD$_{Mn}$, and COD$_{Cr}$ showed 47.6%, 21.3% and 22.1%, respectively. 2. When NaOCI was added at level of 100 ppm in raw wastewater at pH 3, the reduction of color, COD$_{Mn}$, and COD$_{Cr}$ showed 30.2%, 5.5% and 6.2%, respectively. 3. After coagulation-sedimentation processes by addition of FeSO$_4$ $\cdot$ 7H$_2$O, when NaOCl was added at level of 250 mg/l in supernant, color reduction was 47.8% in aeration and 37.5% in jar-mixing. 4. Color reduction by aeration was higher than that by jar-mixing.

• Journal of the Korea Organic Resources Recycling Association
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• v.13 no.4
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• pp.107-117
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• 2005

The objective of this study was to investigate the proper operation conditions of fenton oxidation such as initial pH, $H_2O_2/Fe^{2+}$ ratio, $H_2O_2/Fe^{2+}$ dosage amount, and neutralizing agent for pretreatment of the livestock wastewater. Fenton oxidation reagents were reacted with the livestock wastewater for 2 hours at 120 rpm and the settling was performed for 2 hours using jar-tester apparatus under the different experimental conditions. And then the supernatant was sampled and measured for the residual $H_2O_2$, $COD_{Cr}$, and SS. The results are as follows; optimum initial pH=4, optimum $H_2O_2/Fe^{2+}$ ratio=10:1, optimum $H_2O_2/Fe^{2+}$ dosage amount=5,000/500 mg/L and $Ca(OH)_2$ as proper neutralizing agent. The removal efficiency of $COD_{Cr}$ and SS were 43% and 84% under those optimal fenton oxidation conditions.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.10
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• pp.731-738
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• 2011

In this study AOPs of $O_3/UV$ radiation, $O_3/Mg(OH)_2/UV$ radiation and $O_3/MgO/UV$ radiation system for phenol treatment in aqueous solution was performed in a laboratory scale circulating batch reacter. Flow rate of ozone 1.0 L/min, ozone concentrations $150{\pm}10mg/L$ was maintained constantly at the above-mentioned oxidation processes. During the oxidation processes the $COD_{Cr}$ and TOC was measured in the composition. The pseudo first-order rate constants of the processes was $5.12{\times}10^{-5}$, $1.19{\times}10^{-4}$ and $1.79{\times}10^{-4}sec^{-1}$, and the activation energy was 3.03, 1.79 and $2.32kcal{\cdot}mol^{-1}$ at $20^{\circ}C$, respectively. It was found that both $Mg(OH)_2$ and MgO had remarkable accelerations on degradation of phenol and removal of COD in water. On this basis, $O_3/MgO/UV$ system is an effective and feasible routes for catalytic ozonation of phenol in water.

• Journal of the Korean institute of surface engineering
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• v.36 no.5
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• pp.413-417
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• 2003

The effect of 0-0.7 ㏖% addition of $Cr_2$$O_3$on the dielectric, pyroelectric, and piezoelectric properties were studied in the (Mg$0.7Pb_{1}$$3/Nb_{2}$3/)$O_3$-$0.3PbTiO_3$(0.7PMN-0.3PT) ceramics with composition near the morphotropic phase boundary. The dielectric constant and loss of the ceramics samples were measured as a function of temperature at various frequencies (0.1-100 KHz). The pyroelectric coefficient was measured by using the Byer-Roundy method as a function of temperature. Dielectric, pyroelectric, and piezoelectric constant achieved the maximum values of 0.4 ㏖% $Cr_2$$O_3$The transition temperature is continuously shifted to lower temperature with an increase of a small amount of $Cr_2$$O_3$.

• Journal of the Korean Ceramic Society
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• v.15 no.2
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• pp.72-78
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• 1978

The vapor pressure of the high melting point oxides, MgO, $Cr_2O_3$, and $MgCr_2O_4$ were measured over the temperature range 1300 to 175$0^{\circ}C$ under vacuum <$10^{-5}$ torr by the Langmuir and the Knudsen method. The Langmuir vapor pressure was increased with elevating temperature and with increasing porosity of the specimen. The difference between the vapor preseures measured by the Langmuir and the Knudsen method was decreased with elevating temperature and the Langmuir vapor pressure finally reached the Knudsen vapor pressure at the melting point when extrapolated. The vapor pressure of other important oxides with high melting points, i.e., $Al_2O_3$, $ThO_2$, $Yb_2O_3$ and $Y_2O_3$ were cited from the references. The Langmuir and the Knudsen vapor pressure of these oxides also showed the same results, i.e., they showed the same value at their melting points.