• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.537-541
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• 2010

Pt-Sn with various ratios was supported on carbon black after pretreatment in an acidic solution by a reduction method. The Pt/Sn ratio was controlled by varying the concentration of each component in the solution, and the influence of the composition on the electrocatalytic activities was investigated. The crystallinity of the synthesized materials was investigated by XRD (X-ray Diffraction), and the oxidation states of both the platinum and tin were determined by XPS (X-ray Photoelectron Spectroscopy). SEM (Scanning Electron Microscopy)-EDS (Energy Dispersive Spectroscopy) was utilized to examine the morphology and composition of the synthesized electrode, and the particle size of the Pt-Sn was analyzed by TEM (Transmission Electron Microscopy). The electrocatalytic activity for oxygen reduction was evaluated in a 0.5 M $H_2SO_4$ solution using a rotating disk electrode system. The activity and stability were found to be strongly dependent on the electrode composition (Pt/Sn ratio). The catalytic activity and stability for methanol oxidation were also measured using cyclic voltammetry (CV) in a mixture of 0.5 M $H_2SO_4$ and 0.5 M $CH_3OH$ aqueous solution. The addition of proper amount of Sn was found to significantly improve both catalytic activity and stability for methanol oxidation.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.3
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• pp.204-214
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• 1993

The purpose of this study was to elucidate the chemical changes and formation of sulfur minerals following reduction and subsequent oxidation of the acid sulfate soils derived from the fluvio-marine plains in Gimhae area. Changes in pH, Eh and water soluble $SO_4$, Fe, Al, K, na and Ca were determined in the soil under the reduced and oxidized conditions. These chemical properties were related to the formation of the pyrite and jarosite, the major sulfur minerals in the acid sulfate soils. On incubation, suspension pH tended to increase with decreaseing Eh in the reduction periods. Jarosite formation was favored by maintaining continuous low pH(below 4.0) and high Eh(above 400mV) during the oxidation periods, however, the conditions were not favorable for the soils with $Ca(OH)_2$. Water soluble K increased by reduction but decreased by oxidation, while the jarosite of the soil with $Ca(OH)_2$ was dissolved even under the oxidation conditon, resulting in rapid increase of water soluble K. The water soluble Ca decreased rapidly, indicating that gypsum was formed with $Ca(OH)_2$ during the oxidation periods. The formation of jarosite was favored by the oxidation condition, and hindered by the reduction condition. But the formation of pyrite was favored by reduction and hindered by oxidation. When the troll was treated with $Ca(OH)_2$, Jarosite was dissolved in both oxidized and reduced conditions.

• Journal of Life Science
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• v.18 no.1
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• pp.9-15
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• 2008

Sulfur containing compounds in garlic have all be used as one of the traditional folk medicine as well as food source. The present study was performed to investigate the antioxidative compounds of 1-methyl-1-cysteine, dimethyl trisulfide and 2-vinyl-4H-1,3-dithiin. The antioxidative activity of sulfur containing compounds on human LDL was investigated by monitoring a thiobarbituric acid substances (TBARS). Sulfur containing compounds inhibited on oxidation of LDL mediated by $CuSO_4$ and macrophages in dose dependent manner with almost completely inhibition at $80{\mu}g/ml$. Antioxidant activities of sulfur containing compounds on LDL oxidation were 2-vinyl-4H-1,3-dithiin, 1-methyl-1-cysteine, and dimethyl trisulfide in order. Inhibitory effects of sulfur containing compounds on oxidation of LDL mediated by $CuSO_4$ and macrophages were degraded at much greater rate than native LDL, the LDL oxidation process was arrested as shown by the lower conjugated dienes formation at the concentration of $60{\mu}g/ml$. Sulfur containing compounds in garlic revealed at high antioxidative activity at low physiological concentration for human LDL oxidation in vitro specially, it was indicated that the antioxidative activity of 3-viny l-4H-1,2-dithiin was higher than that of the other sulfur containing compounds.

• New & Renewable Energy
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• v.4 no.2
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• pp.39-44
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• 2008

Partial oxidation of methane was carried out by ceria-promoted Ni-substituted hydrotalcite-derived catalysts ($Ce_xNi_3$-HTlc ; x=$0.3{\sim}1.2$) in a fixed-bed reactor. The Ce/Ni ratio of 0.3/3 in the catalyst showed the best catalytic activity but the Ce/Ni ratio became higher above 0.3/3, the catalyst became less active in short-term tests. No ceria promoted catalyst was started to decrease $CH_4$ conversion after 20 h but the Ce/Ni ratio 0.3/3 catalyst was kept its stability in long-term tests.

• Journal of Ginseng Research
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• v.5 no.2
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• pp.108-113
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• 1981

Major quality indices for deterioration of red ginseng including oxidation of lipids and change of brown color intensity were periodically investicated during storage of Red Ginseng under various water activity conditions at 3$0^{\circ}C$. The results obtained were summarized as follows. 1. The monolayer moisture contents were 3.25% and 6.3% for red ginseng and red ginseng powder, respectively, and the corresponding water activities were 0.14 and 0.16, respectively. 2. Oxidation of lipids as measured by TBA value increased with an increase in relative humidity and storage period 3. Under storage conditions above 42% R H., brown color intensity also increased in similar fashion to that of oxidation of lipids as relative humidity and storage Period increased 4. It was concluded from above results that water activity of Red Ginseng should be kept less than 0.57 so that red ginseng could Preserve stable qualify.

• Journal of the Korean Chemical Society
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• v.58 no.1
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• pp.80-84
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• 2014

The process of petroleum involves in a large amount of oily wastewater that contains high levels of chemical oxygen demand (COD) and toxic compounds. So they must be treated before their discharge into the receptor medium. In this paper, wet peroxide oxidation (WPO) was adopted to treat the oily wastewater. Central composite design, an experimental design for response surface methodology (RSM), was used to create a set of 31 experimental runs needed for optimizing of the operating conditions. Quadratic regression models with estimated coefficients were developed to describe the COD removals. The experimental results show that WPO could effectively reduce COD by 96.8% at the optimum conditions of temperature $290^{\circ}C$, $H_2O_2$ excess (HE) 0.8, the initial concentration of oily wastewater 3855 mg/L and reaction time 9 min. RSM could be effectively adopted to optimize the operating multifactors in complex WPO process.

• Journal of Korean Society on Water Environment
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• v.18 no.2
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• pp.169-187
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• 2002

The effects of important parameters such as reaction time and pH on the Fenton's process were evaluated using a batch reactor. It was proven that organic materials and heavy metals in leachate could be successfully removed by Fenton's reagent. Favorable operation conditions were investigated. It was observed that the reaction between ferrous iron and hydrogen peroxide with the production of hydroxyl radical was almost complete in 10 minutes. That is, the oxidation of organic materials by Fenton's reagent was so fast that it was complete in 30 minutes with batch experiments. With the formation of carbonic acid, pH of the batch reactor decreased to favorable acidic conditions without acid addition. The oxidation of organic materials in the leachate showed a pH dependence and was most efficient in the pH range of 2-3.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.594-599
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• 2022

In the study, NH₃-SCO (selective catalytic oxidation) reaction activity accodrding to vanadium loading amount were compared when preparing Pt/V/TiO₂. Considering both NH₃ conversion rate and N₂ selectivity, V 2 wt% loading of the catalyst showed the best activity. When the correlation between physical/chemical characteristics and reaction activity was confirmed, it was confirmed that the increase in lattice oxygen and (V³⁺ + V⁴⁺) ratios were active factor. In addition, when the SO₂ durability experiment was conducted using the best catalyst, it was confirmed that the influence was insignificant even if the high concentration of SO₂ was injected.

• KSBB Journal
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• v.5 no.1
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• pp.81-85
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• 1990

Lignin was extracted from the rice straw by using the solvent mixture of buthyl alcohol and distilled water. And the experiment of vanillin production from extracted lignin was performed with the oxidation catalysts; CuO, Cu(OH)2 and CuSO4.5H2O. The optimum conditions of lignin extraction are the reaction temperature 12$0^{\circ}C$ and the mixture of 250mL buthyloloohol, 250mL, distilled water and 25g rice straw in the presence of 2.5g p-toluenesulfonic acid. The yield of vanillin from extracted lignin increased linearly with the increase of reaction temperature. And it increased with the order of Cu(OH)<$_2$ CuO$_4\cdot \;5H_2$Oas oxidation catalysts. The maximum yield of vanillin was 9% in the presence of 2.5%(w/v) CuSO$_4\cdot \;5H_2$O under the following conditions: temperature, 18$0^{\circ}C$; pressure, 13atm; pH 4.0 and reaction time, two hours.

• Analytical Science and Technology
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• v.22 no.2
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• pp.186-190
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• 2009

The oxidation studies of a sulfur to a sulfate ion by various oxyhalide oxidants in organic (thiourea, methionine) and inorganic (sulfate, thiophosphate) compounds were carried out in an acidic solution. The optimized result of the oxidation reaction was obtained when a bromate compound (${BrO_3}^-$) as an oxidant and a 3 M $HNO_3$ solvent were used. The chemical yield for the oxidation of the organic and inorganic sulfur compounds to a sulfate ion was monitored as 80% for thiophosphate, 87% for methionine, and 100% for thiourea and sulfate within 5% RSD. The oxidations of thiourea required at least 1.6 equivalents of the bromate in an acidic solution. In the case of the oxidation of methionine and thiophosphate, the oxidation yields were above 80% if the bromate was used at 20 times higher than that of the substrates. The sulfate ion was quantitatively measured by using a GPC counting of $^{35}S$ followed by precipitates of $BaSO_4$. A quenching correction curve for the $^{35}S$ counting was obtained to use the difference via the precipitate weight result.