• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.127-137
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• 2019

Zr electrorefining is demonstrated herein using Zirlo tubes in a chloride-fluoride mixed molten salt in the presence of $AlF_3$. Cyclic voltammetry reveals a monotonic shift in the onset of metal reduction kinetics towards positive potential and an increase in intensity of the additional peaks associated with Zr-Al alloy formation with increasing $AlF_3$ concentration. Unlike the galvanostatic deposition mode, a radial plate-type Zr growth is evident at the top surface of the salt during Zr electrorefining at a constant potential of -1.2 V. The diameter of the plate-type Zr deposit gradually increases with increasing $AlF_3$ concentration. Scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) and X-ray photoelectron spectroscopy (XPS) analyses for the plate-type Zr deposit show that trace amount of Al is incorporated as Zr-Al alloys with different chemical compositions between the top and bottom surface of the deposit. Addition of $AlF_3$ is effective in lowering the residual salt content in the deposit and in improving the current efficiency for Zr recovery.

• Korean Journal of Microbiology
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• v.55 no.1
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• pp.69-73
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• 2019

During screening of microbes for compounds having cosmetic benefits, we isolated Marinobacter salarius HL2708#2 from lava seawater on Jeju Island, Republic of Korea. The complete genome sequence was determined. Strain HL27080#2 features a circular chromosome of 4,304,603 bp with 57.21% G+C content and a 244,163 bp plasmid with 53.14% G+C. There were 4,180 protein coding sequences identified, along with 49 transfer RNA and 18 ribosomal RNA noncoding genes. The genome harbored genes for the utilization of alcohol, maltose/starch, and monosaccharide as sole carbon sources. Genes responsible for halophilic characteristics and heavy metal resistance could be annotated, as well as aromatic and alkane hydrocarbons. Contrary to the prior report that M. salarius is negative for nitrate and nitrite reduction, nitrate/nitrite reductase along with nitrate/nitrate transporters and nitronate monooxygenase were evident, suggesting that strain HL2708#2 may be able to denitrify extracellular nitroalkenes to ammonia.

• Korean Journal of Heritage: History & Science
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• v.52 no.3
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• pp.240-251
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• 2019

This study examined the manufacturing technology used for the flat iron axes excavated from Ulsan Hadae. Their microstructures were analyzed using metallurgical methods. In addition, a variety of manufacturing technologies were examined and compared using existing research materials on flat iron axes. As a result of analyzing ten flat iron axes, which were excavated in the order that they were laid out in a row in one of the wooden coffin tombs at Ulsan Hadae, Tomb No. 44, it was possible to classify the flat iron axe manufacturing technology and system into three types: 'pure iron - shape processing', 'pure iron - shape processing - carburizing', and 'pure iron - shape processing - carburizing - decarburizing.' All of the flat iron axes were produced by forging, and most of them were made by beating the pure iron into their shapes. In particular, a number of the flat iron axes were reinforced through a carburizing process after shaping the iron. This appears as steel products forming the basis of the steel industry at the time were commonly used as an intermediary material or currency. On the other hand, it was commonly found in all samples that the hardening was not performed after shaping or carburizing. Since the microstructure of the flat iron axes made of pure iron contained a large number of impure inclusions and the result of analyzing the components of the non-metal inclusions showed characteristics of slag which contains a mixture of glass phase and wustite, it is possible that low-temperature reduction was used in the refining process.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.3
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• pp.279-298
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• 2019

This study comprehensively addresses recent progress at KAERI in waste treatment technology to cope with waste produced by pyroprocessing, which is used to effectively manage spent fuel. The goal of pyroprocessing waste treatment is to reduce final waste volume, fabricate durable waste forms suitable for disposal, and ensure safe packaging and storage. KAERI employs grouping of fission products recovered from process streams and immobilizes them in separate waste forms, resulting in product recycling and waste volume minimization. Novel aspects of KAERI approach include high temperature treatment of spent oxide fuel for the fabrication of feed materials for the oxide reduction process, and fission product concentration or separation from LiCl or LiCl-KCl salt streams for salt recycling and higher fission-product loading in the final waste form. Based on laboratory-scale tests, an engineering-scale process test is in progress to obtain information on the performance of scale-up processes at KAERI.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.173-180
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• 2019

This study was conducted to understand factors affecting TSS and heavy metals transport on the road, parking lot and roof. During storm events, heavy metals, which were mostly attached to TSS, were also transported when TSS was washed off in the road, parking lot and roof. This finding may be supported by the significant correlations between TSS load and total and soluble heavy metals load including Cr, Fe, Cu, and Pb (Pearson r value: 0.52 to 0.73; probability p value<0.01). Generation and transport of TSS and heavy metals were greater in the road and parking lot compared to the roof due to vehicular activities, slope and greater catchment areas of these sites. It was found that TSS transport during peak flows of storm events ranges from 65% to 75% implying that by controlling peak flows, TSS transportation to nearby water bodies may be decreased. Depending on the target TSS and heavy metal reduction, sizing of low impact development (LID) technologies and green infrastructures (GI) such as infiltration trench, tree box filter, and rain garden may be calculated. Future researchers were recommended to assess the limitations of the systems and determine the design considerations for these types of facilities.

• Korean Journal of Metals and Materials
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• v.56 no.12
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• pp.885-892
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• 2018

Molybdenum disulfide ($MoS_2$) based electrocatalysts have been proposed as substitutes for platinum group metal (PGM) based electrocatalyst to hydrogen evolution reaction (HER) in water electrolysis. Here, we studied $MoS_2/CNFs$ hybrid catalyst prepared by electrospinning method with heat treatment for polymer electrolyte membrane(PEM) water electrolysis to improve the HER activity. The physicochemical and electrochemical properties such as average diameter, crystalline properties, electrocatalitic activity for HER of synthesized $MoS_2/CNFs$ were investigated by the Scanning Electron Microscope (SEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), Raman Spectroscopy (Raman) and Linear Sweep Voltammetry (LSV). The as spun ATTM/PVP nanofibers were prepared by sol-gel and electrospinning method. Subsequently, the $MoS_2/CNFs$ was dereived from reduction heat treatment of ATTM at the ATTM/PVP nanofibers and carbonization heat treatment. Synthesized $MoS_2/CNFs$ electrocatalyst had an average diameter of $179{\pm}30nm$. We confirmed that the $MoS_2$ layers in $MoS_2/CNF$ electrocatalyst consist of 3~4 layers from the Raman results. In addition, We confirmed that the $MoS_2$ layers in $MoS_2/CNF$ catalyst consist of 7.47% octahedral 1T phase $MoS_2$, 63.77% trigonal prismatic 2H phase $MoS_2$ with 28.75% $MoO_3$ through the XRD, Raman and XPS results. It was shown that $MoS_2/CNFs$ had the overpotential of 0.278 V at $10mA/cm^2$ and tafel slope of 74.8 mV/dec in 0.5 M sulfuric acid ($H_2SO_4$) electrolyte.

• Clean Technology
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• v.26 no.4
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• pp.286-292
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• 2020

This study confirmed the effect of the Cu/CeO2-X catalyst on the CO oxidation activity at low temperature through the catalyst's structure and reaction characteristics. The catalyst was prepared by the wet impregnation method. Cu/CeO2_X catalysts were manufactured by loading Cu (active metal) using CeO2 (support) formed at different calcination temperatures (300-600 ℃). Manufactured Cu/CeO2_X catalysts were evaluated for the low-temperature activity of carbon monoxide. The Cu/CeO2_300 catalyst showed an activity of 90% at 125 ℃, but the activity gradually decreased as the calcination temperature of the CeO2-X and Cu/CeO2_600 catalysts showed an activity of 65% at 125 ℃. Raman, XRD, H2-TPR, and XPS analysis confirmed the physicochemical properties of the catalysts. Based on the XPS analysis, the lower the calcination temperature of the CeO2 was, the higher the unstable Ce3+ species (non-stoichiometric species) ratio became. The increased Ce3+ species formed a solid solution bond between Cu and CeO2-X, and it was confirmed by the change of the CeO2 peak in Raman analysis and the reduction peak of the solid solution structure in H2-TPR analysis. According to the result, the formation of the solid solution bond between Cu and Ce has been enhanced by the redox properties of the catalysts and by CO oxidation activity at low temperatures.

• Clean Technology
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• v.26 no.4
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• pp.239-250
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• 2020

Biomass is an abundant renewable energy resource that can replace fossil fuels for the reduction of greenhouse gas (GHG). Indonesia has a large number of cheap biomass feedstocks, such as reforestation (waste wood) and palm residues (empty fruit bunch or EFB). In general, raw biomass contains more than 20% moisture and lacks calorific value, energy density, grindability, and combustion efficiency. Those properties are not acceptable fuel attributes as the conditions currently stand. Recently, torrefaction facilities, especially in European countries, have been built to upgrade raw biomass to solid fuel with high quality. In Korea, there is no significant market for torrefied solid fuel (co-firing) made of biomass residues, and only the wood pellet market presently thrives (~ 2 million ton yr-1). However, increasing demand for an upgraded solid fuel exists. In Indonesia, torrefied woody residues as co-firing fuel are economically feasible under the governmental promotion of renewable energy such as in feed-in-tariff (FIT). EFB, one of the chief palm residues, could replace coal in cement kiln when the emission trading system (ETS) and clean development mechanism (CDM) system are implemented. However, technical issues such as slagging (alkali metal) and corrosion (chlorine) should be addressed to utilize torrefied EFB at a pulverized coal boiler.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.600-605
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• 2022

In this study, nitrogen oxide (NO_x) removal experiments were performed using a graphene based ceramic filter coated with a V₂O₅-WO₃-TiO₂ catalyst. Graphene oxide (GO) was prepared by Hummer's method using graphite, and the reduced graphene oxide was produced by reducing with hydrazine (N₂H₄). Vanadium (V), Tungsten (W), and Titanium (Ti) were coated by the sol-gel method, and then a metal oxide-supported filter was prepared through a calcination process at 350 ℃. A NO_x removal efficiency test was performed for the catalytic ceramic filters with UV light in a humid condition. When graphene oxide (GO) and reduced graphene oxide (rGO) were present on the filter, the NOx removal efficiency was superior to that of the conventional ceramic filter. Most likely, this is due to an improvement in the adsorption properties of NOx molecules on graphene coated surfaces. As the concentration of graphene increased, higher NO_x removal efficiency was confirmed.

• Particle and aerosol research
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• v.17 no.2
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• pp.21-27
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• 2021

We developed non-metallic electrodes that can replace metallic electrodes of the electrostatic precipitator(ESP) for the purpose of light weight, corrosion resistance, cost reduction. We manufactured three types of collection electrodes made of stainless steel (M), Carbon ink coating layer-Plastic sheet-Carbon ink coating layer (CPC), and Plastic sheet-Carbon ink coating layer-Plastic sheet (PCP). We studied the collection efficiency of a two-stage ESP using oil mist particles with and without collection stage by changing the flow rate, the material of collection electrode, and the applied voltage of the pre-charger module and the collection module. Here we measured concentrations of particles at diameters of 0.45 ㎛ (CMD; count median diameter) and 3.0 ㎛ (MMD : mass median diameter), as well as PM_2.5 and PM₁₀. As a result of the experiment, two-stage ESP had 22~25% higher collection efficiency in PM_2.5 than one-stage ESP at the same applied voltage. The difference in collection efficiency by varying the materials of collection electrodes was less than 5%. The weight of the non-metallic electrode was only one eighth the weight of the metal electrode. CPC electrode had a thickness of 0.27 mm, which was 1.5 times thinner than a thickness of PCP electrode, so when the flow rate increased, the CPC electrodes couldn't be kept at equal intervals due to the fluttering unlike PCP electrodes. In addition, the PCP-CPC collection module of the present experiment followed the theoretical efficiency based on Deutsch equation and Cochet's charging theory.