• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.999-1005
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• 1996

Pt catalyst on carbon black was prepared by colloidal method, ion exchanging method and methanol reducing method. The colloidal method has been used generally. At ion exchanging method, $H^+$ of functional group on carbon surface made by oxidation treatment was exchanged with Pt ion. At methanol reducing method, Pt was impregnated on carbon to reduce by methanol contained with surfactants. With TEM and XRD, Pt particle size impregnated on carbon by various methods was $30{\sim}50{\AA}$. Loading yield was about 100%, loading yield of ion exchanging method was 99.92% by DCP analysis and 99.87% by combustion method. Within 60 hour, current density of oxygen reduction was $460mA/cm^2$ at 0.7V(vs. RHE) at colloidal method. It was the better performance than catalyst prepared by ion exchanging, methanol reducing method. But, it was shown some decrease of performance for long operation time(after 100hour), catalyst prepared by methanol reducing method was shown stable performance.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.364-371
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• 2015

For the cost down of polymer concrete, It is very important to reduce the use amount of polymer binder, which occupies most of the production cost of polymer concrete. Fly ash and atomizing reduction steel slag are spherical materials obtained from industrial by-products. Spherical atomizing reduction steel slag was manufactured using steel slag from reduction process of ladle furnace by atomizing technology. To investigate the physical properties of polymer concrete, polymer concrete specimens were prepared with the various proportions of polymer binder and replacement ratios of atomizing steel slag. Results showed that compressive and flexural strengths of the specimens were remarkably increased with the addition amount of polymer binder and the replacement ratios of atomizing steel slag. In the hot water resistance test, compressive strength, flexural strength, bulk density and average pore diameter decreased but total pore volume and pore diameter increased. We found that polymer concrete developed in this study reduced the amount of polymer binder by 18.2% compared to the conventional product because of the remarkable improvement of workability of polymer concrete using spherical fly ash and atomizing reduction steel slag instead of calcium carbonate (filler) and river sand (fine aggregate).

• Korean Journal of Environmental Agriculture
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• v.17 no.3
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• pp.239-245
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• 1998

To investigate the formation of bound residue with soil organic materials by oxidative coupling, nitroaromatics and their reduced metabolites, the insecticide parathion and the herbicide asulam were incubated with oxidoreductase, laccase or horseradish peroxidase, in the presence or absence of humic monomers. Most of aminotoluenes and amino-nitrophenols were completely transformed while most of nitrotoluenes and nitrophenols remained unchanged by a lactase or horseradish peroxidase in the presence or absence of humic monomers. Amino-nitrotoluenes were not transformed without humic monomers, but the addition of various humic monomers caused a considerable difference in the transformation of amino-nitrotoluenes by a lactase or horseradish peroxidase. Amino-nitrotoluenes were most transformed in the presence of catechol, syringaldehyde and protocatechuic acid. The insecticide parathion with nitro group and its metabolite were not mostly transformed in the presence or absence of humic monomers. The herbicide asulam with amino group remained unchanged without humic monomers as well, but the stimulating effect on the transformation of asulam was caused by the addition of catechol, syringaldehyde, protocatechuic acid or caffeic acid with a lactase.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.2
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• pp.110-123
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• 2021

We investigated geochemical constituents of pore-water and sediment, rates of organic carbon (C_org) oxidation and sulfate reduction (SR), and benthic nutrient flux (BNF) to elucidate characteristic of C_org oxidation and its control in the coastal area near Lake Shihwa. The study sites were selected in the vicinity of Soraepogu (E0), Songdo tidalflat (E1) and Oido dock (E3) and in front of floodgate Shihwa tidal plant (E5). The C_org contents in the sediments and concentrations of ammonium and phosphate in pore water exhibited the highest value at EO, and gradually decreased toward the outer sea (E1, E3, E5). Rates of anaerobic C_org oxidation (260.6 mmol C m^-2 d^-1) and SR (91.4 mmol S m^-2 d^-1) at E0 were 4-9 and 6-54 times higher than at the site of outer sea (E1, E3, E5). Rates of SR at E3 and E5 accounted for 11-23% of anaerobic C_org oxidation, whereas it comprised 47-70% of anaerobic C_org oxidation at E0 and E1. Rates of C_org oxidation and SR showed a highly positive correlation with the concentration of dissolved organic carbon (r² = 0.795 and 0.777, respectively). The BNF at E0, E1, and E3 accounted for 120-510% and 26-178%, respectively, of the N and P required for primary production in the water column. Overall results suggest that the C_org oxidation in the sediment controlled by concentration of dissolved organic carbon in the pore water and the excessive C_org oxidation stimulates the benthic nutrient flux, which may cause a phytoplankton bloom in the water column.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.379-384
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• 2017

An electrochemical reduction of a mixture of NiO and rare earth oxides has been conducted to increase the reduction degree of rare earth oxides. Cyclic voltammetry (CV) measurement was carried out to determine the electrochemical reduction behavior of the mixed oxide in molten LiCl medium. Constant voltage electrolysis was performed with various supplied charges to understand the mechanism of electrochemical reduction of the mixed oxide as a working electrode. After completion of the electrochemical reduction, crystal structure of the reaction intermediates was characterized by using an X-ray diffraction method. The results clearly demonstrate that the rare earth oxide was converted to RE-Ni intermetallics via co-reduction with NiO.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.153-157
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• 2004

다양한 혐기성 조건에서 다환방향족탄화수소(PAHs)로 오염된 토양의 미생물 분해 연구를 수행하였다. 대표적인 다환방향족탄화수소인 phenanthrene과 fluorene을 토양과 물에 오염시켜서 약 100일 동안 저감정도를 관찰하였고, 실제 다환방향족탄화수소로 오염된 현장 토양을 이용 혐기성하에서 다환방향족탄화수소의 생분해 가능성을 확인하였다. 미생물 접종원은 혐기성 조건에서 다환방향족탄화수소에 노출시킨 슬러리가 사용되었다. 황산염 환원조건, 질산염 환원조건, 메탄생성조건 등의 다양한 혐기성 조건에서 실험을 수행한 결과, 메탄생성조건 > 질산염 환원조건 > 황산염 환원조건의 순서로 분해가 잘 일어났다. 또한 현장오염토양의 경우 34일간 처리 후 메탄생성조건에서 최대 72%의 분해율을 보였다.

• 한국전기화학회:학술대회논문집
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• 2001.06a
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• pp.231-236
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• 2001

용융탄산염 연료전지용 anode의 creep 현상을 개선하기 위해 $Ni-5wt.\%Al$ green sheet를 사용하여 다양한 소결조건을 적용, $Al_2O_3$를 형성시킨 전극을 제조하고 그 $Al_2O_3$의 형태에 따른 creep 특성에 대해 연구하였다. 소결은 각각 환원분위기, 완전산화-환원분위기, 부분 산화-환원분위기의 서로 다른 분위기에서 진행하였는데, 부분산화-환원분위기로 소결한 경우 Ni-Al 고용체 네트워크를 깨드리지 않고 $A1_2O_3$를 미세한 입자형태로 분산시킬 수 있었다. 그리고, 상기의 방법으로 제조된 anode를 $650^{\circ}C$에서 100psi로 가압하면서 creep test를 실시한 결과 약 $2.3\%$의 변형율을 나타내었다.

• Korean Journal of Environmental Agriculture
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• v.24 no.3
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• pp.203-209
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• 2005

Objective of this research was to assess the effectiveness of the different sources of the zero-valent irons (ZVIs) on the reduction of the toxic Cr(VI) to the nonhazardous Cr(III) in an aqueous solution. The physical and chemical properties of the six ZVIs were determined. Particle size and specific surface area of the ZVIs were in the ranges of $85.55{\sim}196.46{\mu}m\;and\;0.055{\sim}0.091m^2/g$, respectively. Most of the ZVIs contained Fe greater than 98% except for J (93%) and PU (88%). Reduction efficiencies of the ZVI for Cr(VI) reduction were varied with kinds of ZVIs. The J and PU ZVIs reduced 100% and 98% of Cr(VI) in the aqueous solution, respectively, within 3 hrs of reaction. However, PA, F, Sand J1 reduced 74, 65, 29 and 11% of Cr(VI), respectively, after 48 hrs. The pH of the reacting solution was rapidly increased from 3 to $4.34{\sim}9.04$ within 3 hrs. The oxidation-reduction potential (Eh) of the reacting solution was dropped from 600 to 319 mV within 3 hrs following addition of ZVIs to the Cr(VI) contaminated water. The capability of ZVIs for Cr(VI) reduction was the orders of PU > J > PA > F > S > J1, which coincided with the capacities to increase the pH and decrease the redox potentials. Results suggested that the reduction of Cr(VI) to Cr(III) was derived from the oxidation of the ZVI in the aqueous solution.

• Journal of the Korea Organic Resources Recycling Association
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• v.4 no.1
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• pp.13-21
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• 1996

For treating tannery wastewater containing high sulfate and heavy metals, test was performed to assess their performance, competition between SRB (sulfate reducing bacteria) and MPB (methane producing bacteria), and the activity of MPB according to change of chromium concentrations. COD removal efficiency was above 70% at VLR (volumetric loading rate) of 2.0 gCOD/I.day and HRT (hydraulic retention time) of 18hrs at $35^{\circ}C$. In the competition between SRB and MPB, about 15% of the removed COD was utilized by SRB in the begining, but it became 43% at the end. It indicated that MPB was strongly suppressed by the occurrence of significant sulfate reduction since a large electron flow was uptaken by SRB. For the entire experiment, removal efficiencies of chromium concentration were more than 90%. Despite high removal efficiencies of chromium concentration, performance of reactor did not change significantly during the experimental periods. Expecially, chromium (III) is tannery wastewater is less toxic than chromium (VI).

• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.279-285
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• 2017

In this study, the study of the selective catalytic oxidation (SCO) for controlling the $NH_3$ at $200{\sim}350^{\circ}C$ range was investigated. Physicochemical properties of the catalysts were determined using XRD and XPS analysis. In the case of catalytic activity according to thermal treatment condition, the reduction catalyst showed better activity than that of using the calcination catalyst. It was confirmed that the valence state of reduction catalyst was mainly $Pt^{2+}$ and $Pt^0$ as analyzed by XPS. Also, when comparing the reaction activities of $Pt/TiO_2$ catalysts according to the reduction temperature, the $NH_3$ conversion of the catalyst reduced at $700^{\circ}C$ showed the most excellent activity. However, the best activity of $NH_3$ conversion to $N_2$ was obtained for the catalyst reduced at $600^{\circ}C$.