• Korean Chemical Engineering Research
• /
• v.48 no.2
• /
• pp.275-282
• /
• 2010

A characteristic study of aqueous chlorine dioxide generation from sodium chlorite($NaClO_2$) by an undivided electrochemical cell with different anode materials were performed. $IrO_2$-coated Ti, $RuO_2$-coated Ti and DSA were used as anode materials and Pt-coated Ti electrode was used as cathode. Various electrochemical cell operating parameters such as cell residence time($t_R$), initial feed solution pH, sodium chlorite and sodium chloride(NaCl) concentration and applied current for the generation of chlorine dioxide in an un-divided cell were investigated and optimized. Estimated optimal cell residence times in $IrO_2$-coated Ti, $RuO_2$-coated Ti and DSA anode material systems were around 2.27, 1.52 and 1.52 sec, respectively. Observed optimum initial feed solution pH was around 2.3 in all anode material systems. Optimum sodium chlorite concentrations in $IrO_2$-coated Ti, $RuO_2$-coated Ti and DSA anode systems were around 0.43, 0.43 and 0.32 g/L, respectively. Optimum electrolyte concentration and applied current were around 5.85 g/L and 0.6 A in all anode systems. Current efficiencies of $IrO_2$-coated Ti, $RuO_2$-coated Ti and DSA anode systems under optimum conditions were 79.80, 114.70 and 70.99%, respectively. Obtained energy consumptions for the optimum generation of chlorine dioxide were 1.38, 1.03 and $1.61W{\cdot}hr/g-ClO_2$, respectively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.7 no.4
• /
• pp.207-212
• /
• 2009

In this study, a thermal behavior of $PrCl_3$ as one of the lanthanide chlorides in LiCl-KCl molten salts was investigated in an oxidizing condition. First, a thermo-gravimetric analysis (TGA) of $PrCl_3$ was carried out by an injection of $O_2$ gas. Based on the results, an oxidation of $PrCl_3$ in the molten salts was performed by sparging $O_2$ gas with changing temperatures. According to the TGA data of $PrCl_3$, a dissociation of $PrCl_3$ occurred rapidly by about $380^{\circ}C$ and a conversion of $PrCl_3$ to $PrCl_3$ was completed at about $600^{\circ}C$. The thermal behavior of $PrCl_3$ in LiCl-KCl molten salts by sparging $O_2$ gas was similar to that of $PrCl_3$ in the TGA test, and PrOCl as a insoluble compound in the molten salts was precipitated into the bottom of the molten salts. A conversion of $PrCl_3$ to PrOCl in the molten salts occurred actively at a higher temperature than $650^{\circ}C$. And it would be possible to estimate a conversion status of $PrCl_3$ to PrOCl by measuring a $Cl_2$ concentration in a flue gas generated from an oxidation test of $PrCl_3$ in LiCl-KCl molten salts.

• Journal of the Korean Chemical Society
• /
• v.50 no.4
• /
• pp.328-337
• /
• 2006

purpose of this study was to find out problems in experiments for electrolysis of an aqueous CuCl2 solution in high school science textbooks and to suggest an improved experiment considering students' capability of experimenting and laboratory safety in high schools. For this study, the experiments for electrolysis of an aqueous CuCl2 solution presented in 11 high school science textbooks were classified by their experimental methods. After high school chemistry teachers performed the experiments as presented in the high school science textbooks, an analysis was performed on problems of the experiments, and an improved experiment was devised. According to the results of this study, in the experiments for electrolysis of an aqueous CuCl2 solution using a U type tube and a U type tube with branch, reaction velocity of the electrolysis was slow, therefore, a side reaction was generated. In the experiment using a beaker, reaction of each electrode could not be observed separately. And in the experiment using an electrolysis instrument, it was difficult to identify property of the reaction product. In the improved experiment using a reaction vessel of ㅂshape, reaction velocity of the electrolysis was fast, reaction of each electrode could be observed separately, and the side reaction decreased. From these results, it was suggested that the improved experiment would help high school students understand scientific conception regarding electrolysis.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.7
• /
• pp.726-731
• /
• 2005

Sedimentation is treated as the most important unit process in waterworks, and plays great role on turbidity removal efficiency. Rectangle sedimentation basin is the most widely accepted sedimentation process. But it has some problems with short-circuit flow and density flow caused by temperature and influent turbidity variation. To solve these problems, installation of rectification wall was suggested, but not generally fully accepted in field. Because hole of rectification wall cause jet flow. In this research, use of moving baffle was investigated. Moving baffle was designed to induce uniform velocity at every section of water flow. The baffle walls was made from soft fiber materials. The baffle walls with flow of sedimentation basin moves at same speed. It is like that it controls density flow and short-circuit flow and induce uniform velocity at every section of water flow in sedimentation basin. When moving baffle was operated retention time of sedimentation basin was extended to 1 hours. When it talked again and the effluent time of highest concentration of the chlorine ion from 100 minutes was extended to 160 minutes. Turbidity removal efficiency was tested with different operation modes(continuous and batch) with influent turbidity and retention time. It was revealed that turbidity removal efficiency carl be improved up to 36%(continuous mode) and 58%(batch mode) respectively. Consequently if moving baffle introduces in Rectangle sedimentation basin, it forecasts that the turbidity improvement above 30% will be possible.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.2
• /
• pp.170-176
• /
• 2005

This study was conducted to investigate the level of PCBs and distribution of PCB congeners in the ambient air of Korea and Japan. The source of PCBs were also studied by a statistical method. The TEQ concentration of PCB in the ambient air of Korea and Japan were between 0.003 and $1.01\;pgTEQ/m^3$(mean value : $0.22\;pgTEQ/m^3$) and between 0.002 and $0.014\;pgTEQ/m^3$ (mean value: $0.007\;pgTEQ/m^3$), respectively. The ambient air of industrial area of Korea showed a fluctuation in PCB concentration than other sampling area. The isomer distribution patterns in the ambient air was more or less similar in all sampling places. In addition, highly chlorinated homologues ($7{\sim}10CB$) were detected in the only Korea industrial area. This observation suggests that there is a possibility of specific source of PCBs in the industrial area. The source identification of PCB in ambient air was performed using multivariate statistical analysis(principal component analysis). As a result, it is estimated that the Korean ambient air was more influenced by combustion process than the ambient air of Japan and also the effect of PCB commercial products was relatively a small.

• Economic and Environmental Geology
• /
• v.49 no.3
• /
• pp.167-179
• /
• 2016

Water quality of Oseepchun, Dogye area, was investigated quantitatively for its origin and hydrogeochemistry in relation to the influence of groundwater. Groundwater appears to be the principal source of Oseepchun from the water-quality monitoring data including redox potentials, composition of dissolved ions and their correlations, hydrogen and oxygen stable isotopic ratios, and the distribution and occurrence of contaminants. Water-quality type of the surface water was grouped by the water-rock interactions as $Ca-HCO_3$ type originated from carbonated bed-rocks in the Joseon Supergroup, (Ca, Mg)-$SO_4$ type related with dissolution of surfide minerals in coal beds of Pyeongan Supergroup, and (Ca, Mg)-($HCO_3$, $SO_4$) type of the mixed one. Locally water pollution occurs by high $SO_4$ from mine drainage and $NO_3$ from waste-treatment facility. Intensive precipitation in summer has no effect on the water type of Oseepchun, but increases the inflow of nitrate and chloride originated from land surface. Results of this study direct that groundwater-surface water interaction is intimate, and thus surface-water resource management should begin with groundwater characterization.

• Journal of the Korea Institute of Building Construction
• /
• v.22 no.6
• /
• pp.553-564
• /
• 2022

Concrete is a representative composite material that shows excellent performance in the construction field. However, it is a brittle and nonhomogeneous material and exhibits weak behavior against bending and tensile forces. To compensate for such weakens, fiber reinforcement has been utilized, and steel fiber has been recognized as one of the best material for such purpose. However, steel fiber can seriously affect the durability of concrete exposed to the marine environment due to the corrosion caused by chlorine ions. This study intended to evaluate the mechanical performance of steel fiber reinforce concrete during and after repeated wet/dry cycles in salt solution. According to the experimental results, there was no reduction in the relative dynamic modulus of concrete during the repeated wet/dry cycles in salt solution for 37 weeks. Flexural strength was not decreased after completion of repeated wet/dry cycles in salt solution. There was no sign of corrosion in steel fibers after visual observation of fractured surface. However, the flexural toughness was decreased, and this is because about half of the concrete specimen showed failure before reaching the maximum displacement of 3 mm. Although repeated wet/dry cycles in salt solution did not cause cracks in concrete through corrosion of steel fibers, specific attention is required because it can reduce flexural toughness of steel fiber reinforced concrete.

• Journal of the Korean Chemical Society
• /
• v.39 no.7
• /
• pp.513-523
• /
• 1995

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are the most concerned toxic organic pollutants to human. Because of their extremely high toxicity and uncertain genotoxic potential, their determination in environmental and biological samples is of great interest. Municipal solid waste incinerator facilities have been reported as the major contributors of dioxins and furans to the environment, and their formation from combustion is a universal phenomenon, everywhere. In this study dioxins and furans were analyzed from the bottom ash produced during combustion in an municipal waste incinerator located in Seoul. The EPA method was modified for sample pretreatment: the soxhlet method was used for extraction and clean-up procedures were performed by using silica and basic alumina, excluding active-carbon. The extract was then analyzed by HRGC/HRMS. A general trend of increase in the amounts of 6∼7 chlorine-substituted dioxins and furans was observed. Total dioxins, furans and 2,3,7,8-TCDD were determined as 8.05 ng/g, 4.75 ng/g, and 6.93 pg/g, respectively.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.7
• /
• pp.49-54
• /
• 2012

This study focuses on the decomposition of pentachlorophenol(PCP) by an electron beam (E-beam) process. To attain this objective, we investigated the reactive species generated from E-beam process during irradiation (reaction time 0.6 s) and G-values of PCP decomposition and effects of pH and $H_2O_2$ as an additive. The effect of pH values was independent on the decomposition of PCP. However, during E-beam irradiation a scavenging effect of added $H_2O_2$ (> 1mM) for the decomposition of PCP was shown, which was supported by the decreased amounts of $Cl^-$ produced by the decomposition of PCP. Meanwhile, oxalic acid and unidentified organic chlorine compounds as by-products were increased by the addition of $H_2O_2$. Thus, in order to enhance the efficiency of PCP decomposition, the E-beam process has to consider a proper concentration of $H_2O_2$ as a well-known source of strong oxidant hydroxyl radical.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.4
• /
• pp.235-242
• /
• 2005

This study is on the evaluation of performance of polymer cement mortar which is used for pre-wetting spray method. Pre-wetting spray method is an epoch-making method to repair concrete structures damaged, which is added a small quantity water preciously to dry mortar to reduce dust and rebound and spray mortar mixed with fixed quantity water at nozzle before spray. The result showed that physical performance such like compressive, flexural and adhesive strength of polymer cement mortar, TS 100 used for pre-wetting spray method was superior to other repair mortar. Also durable performance such as resistance on permeability of chloride ion, carbonation, chemical and freezing-thawing was excellent.