• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1137-1144
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• 2013

$TiO_2$ composites with seven different carbon materials (activated carbons, graphite, carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene oxides, and reduced graphene oxides) that are virgin or treated with nitric acid are prepared through an evaporation method. The photocatalytic activities of the as-prepared samples are evaluated in terms of $H_2$ production from aqueous methanol solution (photo-catalytic reduction: PCR) and degradation of aqueous pollutants (phenol, methylene blue, and rhodamine B) (photocatalytic oxidation: PCO) under AM 1.5-light irradiation. Despite varying effects depending on the kinds of carbon materials and their surface treatment, composites typically show enhanced PCR activity with maximum 50 times higher $H_2$ production as compared to bare $TiO_2$. Conversely, the carbon-induced synergy effects on PCO activities are insignificant for all three substrates. Colorimetric quantification of hydroxyl radicals supports the absence of carbon effects. However, platinum deposition on the binary composites displays the enhanced effect on both PCR and PCO reactions. These differing effects of carbon materials on PCR and PCO reactions of $TiO_2$ are discussed in terms of physicochemical properties of carbon materials, coupling states of $TiO_2$/carbon composites, interfacial charge transfers. Various surface characterizations of composites (UV-Vis diffuse reflectance, SEM, FTIR, surface area, electrical conductivity, and photoluminescence) are performed to gain insight on their photocatalytic redox behaviors.

• Journal of the Korean Electrochemical Society
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• v.3 no.3
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• pp.141-145
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• 2000

Anodically Polymerized conducting Polypyrrole film electrode was employed to Pick up uranyl ion with the type of Gr/ppy, xylenol orange modified electrode. To have Porous and oriented ppy film, NBR was applied as precoating agent. The rate constant of polymerization was $3.22\times10^{-3}s^{-1}$ which was 1.6 times smaller value than bare graphite surface. The deposited amount of uranyl iou on $1.70Ccm^{-2}$ of ppy was $1.55\times10^{-4}g$. The matrix effect in artificial seawater was $6.8\%$. The polymer film electrode has a diffusion controlled process in conduction, but the modified Gr/ppy, $X.O^{4-}UO^+$ type was influenced on the ion doping and electronic conduction of film itself owing to increasing of impedance. The capacitance of electrical double layer was respectively enhanced to 56 and 130 times in Gr/ppy, $X.O.^{4-}$ and Gr/ppy, $X.O^{4-}UO^+$ than Grippy type electrode.

• Journal of the Korean Chemical Society
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• v.38 no.9
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• pp.667-675
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• 1994

The precipitate flotation using $La(OH)_3$ as a coprecipitant was studied for the simultaneous determination of trace three elements in a sea water. Several experimental conditions such as pH, coprecipitant and surfactant were investigated with an artificial sea water. To remove the influence of Cr(VI) the Cr(VI) was reduced to Cr(III) using $NaBH_4$ prior to the flotation. Trace amounts of Cu(II), Co(II) and total Cr in 1.0 l sea water was coprecipitated together with the precipitation of $La(OH)_3$ in the solution of pH 9.8 adjusted with 3.OM NaOH solution. The precipitate was floated by using a mixed surfactant (1 to 8 of each 0.5% ethanolic sodium oleate and sodium dodecylsulfate solution) by bubbling a nitrogen gas. The floats was separated and filtrated from the mother liquor by suction. The precipitate was dissolved in 7.0 M $HNO_3$ solution and then marked to 25.0 ml with a deionized water. These elements were determined by graphite fumace atomic absorption spectrophotometry. This method was applied to determine the elements in the sea water of the Eastern and Western coasts. And the recoveries were over 90.0% in the samples into which given amounts of the analyte elements were spiked.

• Tunnel and Underground Space
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• v.33 no.6
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• pp.483-494
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• 2023

Measurement of the physical properties of rocks or minerals is an important factor in determining the distribution of the underground medium as well as mineral resource investigations. Resistivity and induced polarization, which are widely used in Korea, are methods for measuring electrical properties, which are representative properties of obtaining subsurface information. In order to precisely analyze the exploration data obtained from various sites, it is important to accurately measure the material properties. Electrical properties of rock is measured using two-electrode or four-electrode method. Compared to the four-electrode method, the two-electrode method is generally used because it is very easy to contact the sample and the electrode, but there is a problem in that the impedance of the electrode and the sample is measured together. In this study, the time-domain the induced polarization effects were measured using the 2-electrode method and the 4-electrode method for artificial samples mixed with graphite and cement having induced polarization characteristics, and the results were compared. Although the 4-electrode method has difficulties in installing potential electrodes, it was confirmed that it is effective in measuring electrical properties because it can reduce the problem caused by the impedance of potential electrodes compared to the 2-electrode method.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.418-428
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• 2007

Physical and chemical properties of the aggregate by-products including sludge and crushed dust samples collected from the 21 private companies throughout the country were analyzed to evaluate possible usage of the by-products as artificial soil materials for plantation. The pH of the materials ranged from 8.0 to 11.0. The organic matter content was $2.85g\;kg^{-1}$, and the total nitrogen content and available phosphate content were low as 0.7 percents and $12.98mg\;kg^{-1}$, respectively. Exchangeable $Ca^{2+}$, $Mg^{2+}$, $K^+$, and $Na^+$ were 2.29, 0.47, 0.02 and $0.05cmol\;kg^{-1}$, respectively. Heavy metal contents were lower than the limits regulated by environmental law of Korea. Textural analysis showed that most of the materials were silt loam with low water holding capacity ranged from 0.67 to 7.41 percents, and with low hydraulic conductivity ranged from 0.4 to $2.8m\;s^{-1}$. Mineralogical analysis showed that the aggregate by product materials were mostly composed of silicate, alumina and ferric oxides except calcium oxide dominant materials derived from limestones. The primary minerals were quartz, feldspars and dolomites derived from granite and granitic gneiss materials. Some samples derived from limestone material showed calcite and graphite together with the above minerals. According to the result, it can be concluded that the materials could be used as the artificial soil material for plantation after proper improvement of the physico-chemical properties and fertility.