• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.735-740
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• 2002

In order to improve the anti-fogging property of polymer films, organic-inorganic hybrid coating solutions which have good hydrophilic property and transmission in the range of visible light were synthesized by the sol-gel method. The coating solutions were prepared by adding glycidoxypropyl trimethoxysilane(GPS) to a colloidal silica(15 nm) suspension(Ludox). GPS as silane coupling agent forms strong bonds to the colloidal silica and surrounding polymer matrix and links two different materials together. Solutions prepared by addition of GPS at the acidic condition resulted in coatings that were less prone to cracking, while those at the basic condition caused coatings with more cracking. These resulted in better hydrophilic property and transmission in the range of visible light for the solution prepared at the acidic condition(pH 2). Compared with coatings under acidic conditions, coatings prepared at basic conditions showed worse hydrophilic property and transmission in the range of visible light.

• Membrane Journal
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• v.29 no.2
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• pp.80-87
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• 2019

Dye-sensitized solar cells (DSSCs) have attracted great attention as sustainable energy devices. The efficiency and long-term stability of DSSCs are greatly influenced by electrode materials and electrolytes. In this review, we focused on the electrolytes of DSSCs. Polymer electrolyte membranes have been proposed as an alternative to conventional liquid electrolytes in DSSCs. Conventional liquid electrolytes can exhibit a high efficiency, but due to some problems such as poor long-term stability of device and leakage of liquid, much interest in polymer electrolyte membranes continues to rise and the papers on polymer electrolytes membranes have been extensively reported recently. This review covers the concept and development of polymer electrolyte membranes for DSSCs, and discusses the efficiency and electrochemical properties of DSSCs, highlighting the modification of polymer matrix, the introduction of additives such as organic-inorganic plasticizers and ionic liquids.

• Journal of the Korean Chemical Society
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• v.38 no.12
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• pp.898-907
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• 1994

The solvent extraction of an inorganic trace mercury in sea water samples was studied using zinc diethyldithiocabamate $Zn(DDC)_2$ as chelating agent. The $Zn(DDC)_2$ which maintained the stability of DDC- in the acidic aqueous solution in the course of extraction was synthesized from NaDDC and $ZnSO_4$ in this laboratory. The trace of mercury(Ⅱ) was extracted at pH 3.0 from 100 ml of sea water into 10ml of chloroform containing 0.05 M $Zn(DDC)_2$ by shaking for 5 minutes. And from the organic phase, the $Hg(DDC)_2$ was back-extracted into 10ml of 1 to 1 mixed acid of each 3% (v/v) nitric acid and hydrochloric acid by shaking for 25 minutes. The mercury back-extracted was determined by a cold vapor atomic absorption spectrophotometry. The trace mercury(Ⅱ) was so successfully extracted that this procedure could be applied to its determination in the sea water. That is, the recoveries of mercury in two kinds of samples into which as given amount of Hg(Ⅱ) was spiked were 90.0% and 93.3%, respectively.

• The Korean Journal of Ecology
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• v.17 no.3
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• pp.251-260
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• 1994

Nitrification potential bioassay and terpenoid analyses were performed to determine the roles of terpenoid as an inhibitor of nitrification in the Douglas fir (Pseudotsuga menziesii) forests. The effect of terpenoids in the forest floor was also tested by adding $10{\mu}g/ml$ of four terpenoids(${\alpha}-pinene,{\beta}-pinene,{\gamma}-terpinene, and terpinolene) to mineral soils. The amount of terpenoids in the litter was higher than that in the soil and varied over time, but the amount of terpenoids in the soils was relatively constant. The correlation between the amount of terpenoids in the litter and ammonium oxidation was in inverse proportion to that in the mineral layers $(r^2=0.678)$. Inhibition of ammonium oxidation by terpenoids in the litter was always higher than in the mineral layer, but nitrite oxidation was different from the ammonium oxidation. The fact that there was greater nitrate production from ammonium in the mineral layer than in the forest floor layer seems to be due to the less amounts of terpenoids in the mineral layer. The result of the experiment in which four terpenoids were added to the mineral layer suggests that, after some lag time, the four terpenoids were effective in inhibiting ammonium oxidation. However, nitrite oxidation did not appear to be affected by the four terpenoids. Accordingly, all of our results suggested that terpenoids in Douglas fir forests apparently would act as a part of the inhibitors of nitrification.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.135-140
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• 1998

The constituents of deposits on paper machine and holes/spots in paper have been analyzed by a combination of analytical techniques, such as FTIR, Py-GC-MS, and EDS. FTIR spectroscopy was used prior to Py-GC-MS and EDS analysis, as a preliminary analysis. The analysis of organic components was carried out with a pyrolysis unit connected to a GC-MS, and inorganic components in ash were analyzed by SEM equipped with an EDS analyzer after pyrolysis at $590^{\circ}C$. The deposits on the dryer section were complex pitch, which was the mixture of the organic components of fatty acid ester and starch, and the inorganic components of talc, clay, and calcium carbonate. The complex pitch was estimated to come from the coated broke. We knew the deposits on the metering rod of sym-sizer were associated with the interaction of unstable alkyl keten dimer(AKD) and $CaCO_3$. The compositions of holes or spots varied considerably and were associated with chemical interaction within the system. The holes, spots, and blotches in the finished paper were PE and PP from pulp sources, complex pitch that were caused by the interaction of the different additives in the system, polymer such as flexible PVC that was used for the prop of palette, and hot melt as adhesives that came from the inadequate handling of broke. In addition, we identified that poly(caprolactam) which is used for forming fabrics or press felts, could be mixed with the raw materials by accident and results in streaks on coating.

• Resources Recycling
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• v.33 no.3
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• pp.30-37
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• 2024

In this study, we investigated the separability of vanadium and tungsten from spent SCR (Selective Catalytic Reduction) catalyst leach solution by reduction of vanadium and solvent extraction using Alamine 336 and conducted experiments to optimize process conditions. It is difficult to separate vanadium and tungsten due to their similar chemical behavior, but tungsten can be selectively extracted from acidic solution when vanadium extraction is prevented by reducing anionic pentavalent vanadium to cationic tetravalent vanadium. The results showed that NaHSO₃ was most suitable as a reducing agent, and the extraction efficiency of vanadium decreased and the separation efficiency increased as the amount of reducing agent added, reaction time, and temperature increased. When reducing NaHSO₃ 1.5 eq, 60 min, and 60℃, which are optimal conditions of reduction, vanadium and tungsten were effectively separated with vanadium extraction efficiency of 5.8%, tungsten extraction efficiency of 99%, and separation factor of vanadium and tungsten of 7,564.

• Korean Journal of Food Science and Technology
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• v.35 no.1
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• pp.15-22
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• 2003

Nutritional compositions of three Tochukaso species (Paecilomyces tenuipes hosted by Larva and pupa, Cordyceps militaris, C. sinensis) were compared. Fruiting body and host fractions were separately analyzed. Fruiting body fraction of P. tenuipes (36.6%) hosted by larva was higher than that hosted by pupa (10.2%), an indication that the quality of the former is superior to the latter. Carbohydrate content of C. sinensis (39.6%) was $2.5{\sim}7$ times higher than those of others, probably due to the presence of polysaccharides. Protein and crude lipid contents of C. sinensis and C. militaris were 25.8 and 10.3%, and 75.1 and 3.9%, respectively. C. sinensis showed the lowest Ca content and $30{\sim}75$ times higher Fe content among the samples tested. Vitamin A content of C. militaris was 308.9 IU/100g, two fold higher than those of the other species. Saturated fatty acid content was the highest in P. tenuipes (pupa, 27.7%), whereas unsaturated fatty acid was the highest in P. tenuipes (larva, 83.3%). Aspartic acid, glutamic acid, and glycine were abundant in all species. Cordycepin content of C. militaris was $20{\sim}50$ times higher than those of the other species.

• Applied Biological Chemistry
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• v.11
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• pp.83-88
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• 1969

94 Cellulase producing strains were isoated from soils, composts, rotten woods and straws, and gastric contents and feces of herbivorous animals in various places. Among them, the strain MC-9, MC-10, MC-53 and MC-61 were found to be highly active in the degradation of carboxy methyl cellulose. Their cultural conditions adequate for the cellulase formation and effects of inorganic salts and various organic substances added to the wheat bran media were investigated. The results obtained are as follows; 1. Optimum conditions for the cellulase formation were MC-9: pH 5.5, temp. $35^{\circ}C$, incubation time 5 days, MC-10: pH 5.5-6.0, temp. $30^{\circ}C$, incubation time 5 days, MC-53: pH 3.5, temp. $30^{\circ}C$, incubation time 5 days, MC-61: pH 3.5-4.0, temp. 30-$35^{\circ}C$, incubation time 5 days. 2. Their cellulase activity in their optimum conditions were MC-9: CMC-LP(liquefying power). 87.7%, CMC-SP(saccharifying power) 3.20 glucose mg./gm. of the cultures/min., MC-10: CMC-LP 82.9%, CMC-SP 2.48 glucose mg./gm. of the cultures/min., MC-53: CMC-LP 72.4%, CMC-SP 1.76 glucose mg./gm. of the cultures/min., MC-61: CMC-LP 87.1%, CMC-SP 2.08 glucose mg./gm. of the cultures/min. 3. Additions of inorganic salts to the wheat bran media were not significant for the cellulase formation, but additions of soybean film and orange-peel pomace promoted the CMC-liquefying power 3 to 5 percent in wheat bran cultures of the strains.

• Journal of the Korean Ceramic Society
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• v.39 no.5
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• pp.503-510
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• 2002

Silicon carbide candle filters for the pressurized fluidized bed combustion system were fabricated by extrusion process. Carbon black was added to control the porosity. Inorganic additives such as clay and calcium carbonate were added to exhibit appropriate strength. Silicon carbide layer with a finer pore size (mean pore diameter ~$10{\mu}m$) was coated on the silicon carbide support layer (mean pore diameter ~$47{\mu}m$, porosity ∼40%). After that, the filter was sintered at 1400${\circ}C$ in air. We evaluated the filtration performances of the filter at 500${\circ}C$ and $5kgf/cm^2$ of pressure. As a result, high separation efficiency, >99.999% was measured. It is expected that silicon carbide candle filter can be successfully used for the pressurized fluidized bed combustion system.

• Korean Journal of Materials Research
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• v.25 no.2
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• pp.75-80
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• 2015

The carbon dioxide($CO_2$) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical method to reducing $CO_2$ for building materials is the addition of slag and fly ash, like pozzolan material, while another method is reducing $CO_2$ production by carbon negative cement development. The MgO-based cement was from the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements could improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, the basic research for magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as main starting materials, as well as silica fume, fly ash and blast furnace slag for the mineral admixture, were carried out for industrial waste material recycling. In order to increase the hydration activity, $MgCl_2$ was also added. To improve hydration activity, $MgCO_3$ and serpentinite were fired at $700^{\circ}C$ and autoclave treatment was conducted. In the case of $MgCO_3$ as starting material, hydration activity was the highest at firing temperature of $700^{\circ}C$. This $MgCO_3$ was completely transferred to MgO after firing. This occurred after the hydration reaction with water MgO was transferred completely to $Mg(OH)_2$ as a hydration product. In the case of using only $MgCO_3$, the compressive strength was 3.5MPa at 28 days. The addition of silica fume enhanced compressive strength to 5.5 MPa. In the composition of $MgCO_3$-serpentine, the addition of pozzolanic materials such as silica fume increased the compression strength. In particular, the addition of $MgCl_2$ compressive strength was increased to 80 MPa.