• Journal of Soil and Groundwater Environment
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• v.17 no.2
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• pp.15-21
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• 2012

MTBE (Methyl tertiary-butyl ether) has been commonly used as an octane enhancer to replace tetraethyl lead in gasoline, because MTBE increases the efficiency of combustion and decreases the emission of carbon monoxide. However, MTBE has been found in groundwater from the fuel spills and leaks in the UST (Underground Storage Tank). Fenton's oxidation, an advanced oxidation catalyzed with ferrous iron, is successful in removing MTBE in groundwater. However, Fenton's oxidation requires the continuous addition of dissolved $Fe^{2+}$. Zero-valent iron is available as a source of catalytic ferrous iron of MFO (Modified Fenton's Oxidation) and has been studied for use in PRBs (Permeable Reactive Barriers) as a reactive material. Therefore, this study investigated the condition of optimization in MFO-PRBs using waste zero-valent iron (ZVI) with the waste steel scrap to treat MTBE contaminated groundwater. Batch tests were examined to find optimal molar ratio of MTBE : $H_2O_2$ on extent to degradation of MTBE in groundwater at pH 7 with 10% waste ZVI. As the results, the ratio of optimization of MTBE to hydrogen peroxide for MFO was determined to be 1:300[mM]. The column experiment was conducted to know applicability of MFO-PRBs for MTBE remediation in groundwater. As the results of column test, MTBE was removed 87% of the initial concentration during 120days of operational period. Interestingly, MTBE was degraded not only within waste ZVI column but also within sand column. It means the aquifer may affect continuously the MTBE contaminated groundwater after throughout the waste ZVI barrier. The residual products showed acetone, TBF (Tert-butyl formate) and TBA (Tert-butyl acetate) during this test. The results of the present study showed that the recycled materials can be effectively used for not only a source of catalytic ferrous iron but also a reactive material of the MFO-PRBs to remove MTBE in groundwater.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.847-860
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• 2020

This study was conducted into combustion characteristics and gases generated by the combustion of charcoal and agglomerated charcoal distributed in the domestic using a combustion chamber based on the average space per crater of a charcoal-grilled restaurant in South Korea. Each of the three types of charcoals and agglomerated wood charcoals was analyzed for fuel and combustion characteristics. In addition, the concentration changes of CO, CO₂, NO_x, and O₂ were measured for 20 minutes depending on ventilation. As a result, CO yield without ventilation was measured in the range of 1390 to 4703 ppm, and CO yield with ventilation decreases about 29.8% to 57.4%. CO₂ yield without ventilation was measured in the range of 1.34% to 2.42%, and CO₂ yield was about 44.1% to 53.6% when the emission was more than about 1.5% at 10 minutes. The NOx yield was divided into two cases where the NO_x yield was continuously increased because of incomplete combustion, emitted ranging from 29 ppm to 47 ppm, and where emission was constant after 1 minute in the range of 9 ppm to 18 ppm. The NO_x yield with ventilation tends to be similar to the without ventilation, and NO_x yield decreases up to 62.5%. Therefore, it could be used for health risk assessment with the simulation of the usage environment of charcoal and agglomerated wood charcoal.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.8
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• pp.492-497
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• 2015

VOCs (Volatile Organic Compounds) are generally generated in the painting process, or at the company and laundry where use organic solvents. The VOCs consist of various hydrocarbons and has low calorific value due to its dilution with atmospheric air. Therefore, the VOCs are difficult to burn by a conventional fuel combustor. In this study, a novel plasma dump combustor was proposed for the treatment of low calorific VOC gases. This combustor was designed a combination of the characteristics in a plasma burner, a dump combustor and a 3D matrix burner. The combustor has good structure for maintaining enough residence time and reaction temperature for stable flame formation and VOC destruction. For investigating the performance characteristics of the plasma dump combustor, an experiment was achieved for VOC feed rate, VOC injector position, etc. Toluene was used as a surrogate of VOC. The novel combustor gave better performance than a conventional combustor, showing that VOC destruction rate and energy efficiency were 89.64% and 12.27 kg/kWh respectively, at feeding rate of 450 L/min of VOC of 3,000 ppm of toluene concentration.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.2
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• pp.95-104
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• 2005

Effects of the aluminum melting temperature, melting time and a kind of flux agents on the distribution of surrogate nuclide were investigated in the electric furnace at the aluminum melting including surrogate radionuclides(Co, Cs, Sr) in order to establish the fundamental research of the melting technology for the metallic wastes from the decommissioning of the TRIGA research reactor. It was verified that the fluidity of aluminum melt was increased by adding flux agent but it was slightly varied according to the sort of flux agents. The results of the XRD analysis showed that the surrogate nuclides move into the slag phase and then they were combined with aluminum oxide to form more stable compound. The weight of the slag generated from aluminum melting test increased with increasing melting temperature and melting time and the increase rate of the slag depended on the kind of flux agents added in the aluminum waste. The concentration of the cobalt in the ingot phase decreased with increasing reaction temperature but it increased in the slag phase up to 90$\%$according to the experimental conditions. The volatile nuclides such as Cs and Sr considerably transferred from the ingot phase to the slag and dust phase.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.1
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• pp.91-99
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• 2007

It was intended in this study to investigate the effects of various parameters on the chemical reaction or mass transfer yield in a tubular-type nuclear waste treatment equipment. Since such equipments, as a tubular reactor, multistage solvent extractor, and adsorption column, accompany chemical reaction or mass transfer along the fluid-flowing direction, mathematical modeling for each equipment was carried out first. Then their behaviors of the chemical reaction or mass transfer were predicted through computer simulations. The inherent major parameters for each equipment were chosen and their sensitivities. affecting the reaction or mass transfer yield were analyzed. For the tubular reactor, the effects of axial diffusion coefficient and reaction rate constant on the reaction yield were investigated. As for the multistage solvent extractor, the backmixing of continuous phase and the distribution coefficient between fluid and solvent were considered as the major parameters affecting the extraction yield as well as concentration profiles throughout the axial direction of the extractor. For the adsorption column, the equilibrium constant between fluid and adsorbent surface, and the overall mass transfer coefficient between the two phases were taken as the major factors that affect the adsorption rate.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.3
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• pp.189-197
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• 2007

The solubility of U(VI) hydrolysis products was determined by using a laser-induced breakdown detection (LIBD) technique. The experiments were carried out at uranium concentrations in range from $2{\times}10^{-4}\;M\;to\;4{\times}10^{-6}\;M$, pH values between 3.8 and 7.0, the constant ionic strength of 0.1 M $NaClO_4$ and the temperature of $25.0{\pm}0.1^{\circ}C$. The solubility product of U(VI) hydrolysis products was calculated from LIBD results by using the hydrolysis constants selected in NEA-TDB. The solubility product extrapolated to zero ionic strength, ${\log}K^{\circ}_{sp}=-22.85{\pm}0.23$ was calculated by using a specific ion interaction theory (SIT). The spectral features of ionic species in uranium solutions were investigated by using a conventional UV-visible absorption spectrophotometer and a fluorophotometer, respectively, $(UO_2)_2(OH)_2^{2+}\;and\;(UO_2)_3(OH)_5^+$ were dominant species at uranium concentration of $2{\times}10^{-4}\;M$.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.1
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• pp.1-14
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• 2017

For the removal of cesium (Cs) from high radioactive/high salt-laden liquid waste, this study synthesized a highly efficient composite adsorbent (potassium cobalt ferrocyanide (PCFC)-loaded chabazite (CHA)) and evaluated its applicability. The composite adsorbent used CHA, which could accommodate Cs as well as other molecules, as a supporting material and was synthesized by immobilizing the PCFC in the pores of CHA through stepwise impregnation/precipitation with $CoCl_2$ and $K_4Fe(CN)_6$ solutions. When CHA, with average particle size of more than $10{\mu}m$, is used in synthesizing the composite adsorbent, the PCFC particles were immobilized in a stable form. Also, the physical stability of the composite adsorbent was improved by optimizing the washing methodology to increase the purity of the composite adsorbent during the synthesis. The composite adsorbent obtained from the optimal synthesis showed a high adsorption rate of Cs in both fresh water (salt-free condition) and seawater (high-salt condition), and had a relatively high value of distribution coefficient (larger than $10^4mL{\cdot}g^{-1}$) regardless of the salt concentration. Therefore, the composite adsorbent synthesized in this study is an optimized material considering both the high selectivity of PCFC on Cs and the physical stability of CHA. It is proved that this composite adsorbent can remove rapidly Cs contained in high radioactive/high salt-laden liquid waste with high efficiency.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.2
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• pp.123-132
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• 2007

This study was performed to evaluate the co- and mutual separation for Am, Cm and RE elements from the simulated multi-component solution equivalent to real HLW level by a Zr-DEHPA(di-(2-ethylhexyl) phosphoric acid containing Zirconium)/$NDD(n-dodecane)-HNO_3$ extraction system. Zr-DEHPA was self-synthesized and the optimal condition of (15g/L Zr-1M DEHPA)/NDD-1M $HNO_3$ was selected taking into consideration of prevention of the third phase, and effects of concentration of DEHPA, nitric acid and impregnant amount of Zr on the co-extraction of Am, Cm and RE. In that condition, the extraction yields were 81% (Am), 85% (Cm), more than 80% (RE elements), 98% (Mo), 85% (Fe), 98% (U), 73% (Np), and less than 5% (other elements) so that the system developed for the co-extraction of Am-Cm/RE was proved to be available. For that, however, U, Np, Mo and Fe was elucidated to have to be removed in advance, and Zr inducing the third phase formation was found to be practically excluded. The co-extracted Am-Cm/RE were sequentially separated in an order of Am-Cm (stripping agent : 0.05 M DTPA-1M Lactic acid of pH 3.6)${\rightarrow}RE$ (stripping agent : 5M $HNO_3$), and then their separation factors were evaluated. At above conditions, Am of 65.4%, Cm of 63.9%, RE (except for Y) of more than 85% were stripped.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.2
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• pp.133-143
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• 2007

This study was performed to evaluate the co- and sequential separation of Tc, Np and U from the simulated multi-component HLW solution by a TBP (tributyl phosphate)-TOA (tri- octyl amine)/NDD $(n-dodecane)-HNO_3$ extraction system. An optimal condition of (30% TBP-0.5% TOA)/NDD-1 M $HNO_3$ was selected by taking account of a prevention of the 3rd phase and effects of concentration of TBP, TOA and nitric acid on the co-extraction of Tc, Np and U. In that condition, the extraction yields were 81% (Tc), 85% (Np), less than 9% (Am and RE elements), about 8% (Pd), and less than 5% (other elements) so that the system developed for the co-extraction of Tc, Np and U was proved to be available. For that, however, more than 99% of Zr was found to be pre-removed. The co-extracted Tc, Np and U were sequentially separated in order of Tc(stripping agent : 5 M $HNO_3$)${\rightarrow}Np$ by reductive stripping (reductive-stripping agent : 0.1 M AHA)${\rightarrow}U$ (stripping agent : 0.01 M $HNO_3$), and then their separation factors were evaluated. At these conditions, 95% of Tc, 98% of Np and 99% of U could be recovered in each step.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.4
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• pp.275-286
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• 2014

This study evaluated the evolution stage and origin of chemical components of 12 boreholes at crystalline bedrock using multivariate statistical and groundwater quality analyses. Groundwater types are mostly belonged to Na(Ca)-$HCO_3$ and Ca-$HCO_3$ types, indicating that directly reaction of cation exchange ($Ca^{2+}{\rightarrow}Na^+$) prevailed. The degree of groundwater evolution is included the range from low to intermediate stage based on field and laboratory analytical conditions. As a result of multivariate statistical analysis, a typical indicator of groundwater contamination, $NO_3$-, has the positive correlation with $Na^+$ and $Cl^-$. The origin of sea spary ($Cl^-$) has the positive correlation with $Na^+$, $SO{_4}^{2-}$, $Mg^{2+}$, and $K^+$, while not correlation with $Ca^{2+}$, $Fe^{2+}$, $HCO_3{^-}$, $F^-$, and $SiO_2$. The concentration of $Cl^-$ and $NO_3{^-}$ belongs to general quality of groundwater and not exceeds over the Korean standard for drinking water. And the negative values of saturation index of minerals are calculated with chemical components in groundwater. Therefore, most of chemical components of groundwater in the study area are originated from natural process between rock and groundwater, whereas some of components are derived from sea spary and anthropogenic sources related to agricultural activities.