• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.352-357
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• 2009

Due to rapid consumption of hydrogen peroxide, large amount of hydrogen peroxide is required when Fenton reaction is applied to the contaminated soil. In this study, acetate was employed as a ligand of $Fe^{2+}$ to enhance the efficiency of removal of phenanthrene by securing the stability of hydrogen peroxide. 0.5 ${\sim}$ 3 times of acetate (2${\sim}$12mM) was added to compare with molar concentration of $Fe^{2+}$. Low initial concentration of hydrogen peroxide was 0.7% to eliminate side effect of removal efficiency. The results showed that hydrogen peroxide lifetime was lasted up to 72 hours, or more than 50 times of normal lifetime. Phenanthrene removal efficiency was improved up to 70% due to stabilized hydrogen peroxide. Ferrous ion was oxidized to ferric ion and oxidation-reduction was repeated during the reaction. Finally ferric ion was reduced to ferrous by $HO_2$. It was confirmed that, due to the influence of hydrogen peroxide, pH was acid region and it remained at the range of 4 ${\sim}$ 5 when 8 mM or more of acetate was added. Acetate which was used as the ligand of Fe was also decomposed by Fenton reaction. The decomposition time of acetate was slower than phenanthrene. Therefore, it was able to come to the conclusion that phenanthrene was superior to acetate at the competition for decomposition. Through the results of this study, it was able to identify the possibilities to improve the efficiency of Fenton reaction in the contaminated soil and its economic feasibility, and to move to more realistic technique through research expanded to neutral pH region.

• Korean Journal of Environmental Agriculture
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• v.39 no.1
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• pp.58-64
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• 2020

BACKGROUND: Most of the researches on the dye removal using ozonation have been focused on the removal efficiency. However, the research on their removal characteristics and mechanism according to the reaction time has been still insufficient. METHODS AND RESULTS: In this study, the effects of initial pH and dye concentration with reaction time on the degradation characteristics of methyl orange (MO) and methylene blue (MB) by ozonation were evaluated. The degradation efficiency of MB by ozonation increased with increasing pH. On the other hand, the degradation efficiency of MO by ozonation did not show a significant difference with varing pH. The both MO and MB by ozonation were decomposed within 30 min irrespective of the dye concentration, but the decomposition rates of dyes were faster at lower initial dye concentration. The decomposition efficiency of total organic carbon (TOC) in each dye solution by ozonation was low, which was found to be effective for partial decomposition such as decolorization rather than complete degradation of the dye. CONCLUSION: Overall, ozonation was an effective method for removing nondegradable dyes. However, it is necessary to study the optimization of dye degradation under various environmental conditions for ozonation.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.316-322
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• 2006

The current study evaluated the technical feasibility of the application of $TiO_2$ photocatalysis for the removal of nocotine which has well known as a representative material of environmental tobacco smoke(ETS). Four different preliminary experiments were performed for the evaluation of nicotine removal using photocatalyst-coated construction materials. The photocatalytic removal of nicotine was investigated for five parameters: dry condition of coating tiles, type of coating sol, number of coatings, relative humidity(RH), and input concentrations. Prior to performing the parameter tests, adsorption of nicotine onto the current experimental system was surveyed. All the variables tested in the present study exhibited to influence the photocatalytic decomposition of Nicotine. A dry condition of high temperature and short dry period presented higher photocatalytic oxidation(PCO) efficiency compared to that of low temperature and long dry period. ST-KO3 sol showed higher decomposition efficiency than E-T Sol. The PCO efficiency increased as the number of coating increased. High humidity and low input concentrations exhibited higher PCO efficiency. Consequently, it is noted that the five parameters tested in the present study should be considered for the application of photocatalyst-coated construction materials in cleaning nicotine in ETS.

• KSBB Journal
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• v.16 no.4
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• pp.389-397
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• 2001

The effect of sludge digestion on the leaching efficiency of heavy metals from sludge by bioleaching with Thiobacillus thiooxidans MET was investigated. The used sludges were a non- and anaerobically digested. The leaching efficiency of heavy metals was strongly dependent on the pH of the sludge solution rather than the sludge condition and stolid concentration. The lower the pH the more heavy metal was leached from 3.0 of pH. The sequent orders of leaching heavy metals were Zn, Cu, and Cr. Although the buffering capacity of non-digested sludge was similar to anaerobically digested sludge, the pH decrease rate of the anaerobically digested sludge solution was faster than that of the non-digested sludge solution due to the higher sulfur oxidation rate of T. thiooxidans MET in the anaerobically digested sludge. The amount of leached heavy metals from the anaerobically digested sludge showed higher than that of non-digested sludge at the same pH value. This result might be caused by the difference of the insoluble metal types, which were contained in the sludge. An increase in sludge solids concentration decreased the leaching efficiency of heavy metals in the range of solids concentration 10 g/L to 70 g/L. The optimum ratio of S° to sludge stolid was 0.1 in both the sludge. The bioleaching process of heavy metals with T. thiooxidans MET showed the disinfecting effect over 90% as well as the reduction effect in sludge weight of 20%.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.292-299
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• 2014

In this study, nitrogen doped carbon felt (CFt) is prepared using thermal oxidation and liquid phase ammonia treatment to improve the efficiency for vanadium redox flow batteries (VRFB). The electrochemical properties of prepared CFt electrodes are investigated using cyclic voltammetry (CV) and charge/discharge test. The XPS result shows that the increase of liquid phase ammonia treatment temperature leads to the increased nitrogen functional group on the CFt surface. Redox reaction characteristics using CV reveal that the liquid phase ammonia treated CFt electrodes are more reversible than the thermally oxidized CFt. When CFt is treated by the liquid phase ammonia at $300^{\circ}C$, VRFB cell energy efficiency, voltage efficiency, and current efficiency are increased about 6.93%, 1.0%, and 4.5%, respectively, compared to those of the thermally oxidized CFt. These results are because nitrogen functional groups on CFt help to improve the electrochemical properties of redox reaction between electrode and electrolyte interface.

• Journal of Applied Biological Chemistry
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• v.50 no.1
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• pp.6-12
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• 2007

Feasibility of laboratory-synthesized zerovalent iron was investigated to remove arsenic from leachates of tailings taken from an Au-Ag abandoned mine. The tailings were seriously contaminated with arsenic, and its potential adverse effect on the ecosystems around the mine seems to be significantly high. Long-term column experiments were conducted for about 3.5 months to evaluate the effectiveness of the synthesized zerovalent iron for removal of arsenic. Over than 95% removal efficiency of As was observed in the zerovalent iron mediated tests. In addition, the XRD data suggest that the corrosion products of ZVI were identified magnetite, maghemite, goethite, and lepidocrocite, all of which support Fe(II) oxidation as an intermediate step in the zerovalent iron corrosion process. The results indicate that arsenic can be removed from the tailing-leachate by the mechanism of coprecipitation and/or adsorption onto those iron oxides formed from ZVI corrosion.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.84-88
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• 2009

The nickel-based alloy Nimonic 80A possesses strength, and corrosion, creep and oxidation resistance at high temperature. The exhaust valves of low speed diesel engines are usually operated at temperature levels of 400-$600^{\circ}C$ and high pressure to enhance thermal efficiency and exposed to the corrosion atmosphere by the exhaust gas. Also, the exhaust valve is subjected to repeated thermal and mechanical loads. So, the nickel-based alloy Nimonic 80A was used for the large exhaust valve spindle. It is composed a 540mm diameter head and a 125mm diameter stem. It is developed large products by hot closed-die forging. Manufacturing process analysis of the large exhaust valve spindle was simulated by closed die forging with hydraulic press and cooled in air after forging. The preform was heated to $1080^{\circ}C$ Numerical calculation was performed by DEFORM-2D, a commercial finite element code. Heat transfer can be coupled with the deformation analysis in a non-isothermal deformation analysis. Mechanical properties of the large exhaust valve spindle were evaluated by the variety of tests, including microstructure observation, tensile, as well as hardness and fatigue tests, were conducted to evaluate the mechanical properties for head part of exhaust valve spindle.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.482-485
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• 2004

We fabricated a hybrid bulk/fully depleted silicon on insulator (FDSOI) complementary metal oxide semiconductor (CMOS) active pixel image sensor. The active pixel is comprised of reset and source follower transistors on the SOI seed wafer, while the pinned photodiode and readout gate and floating diffusion are fabricated on the SOI handle wafer after the removal of the buried oxide. The source of dark current is eliminated by hybrid bulk/FDSOI pixel structure between localized oxidation of silicon (LOCOS) and photodiode(PD). By using the low noise hybrid pixel structure, dark currents qm be suppressed significantly. The pinned photodiode can also be optimized for quantum efficiency and reduce the noise of dark current. The spectral response of the pinned photodiode on the SOI handle wafer is very flat between 400 nm and 700 nm and the dark current that is higher than desired is about 10 nA/cm2 at a $V_{DD}$ of 2 V.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.6
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• pp.547-553
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• 2015

For commercialization of fuel cell electric vehicles, one of the key objectives is to reduce cost of full stack assembly. Regarding Membrane Electrode Assembly, the major issue is to improve fuel cell activation process in the initial Hydrogen Oxidation Reaction and Oxygen Reduction Reaction. In this research, the VD (Vacuum Drying) process has been developed for improvement of activation process. The VD condition is developed by controlling the temperature and degree of vacuum to remove the remaining solvent of electrode. Consequently, the electrode applied to VD process showed the low characteristics such as 3.5% of remaining solvent content and the improved efficiency such as 15% of activation process speed.

• Journal of Korean Society on Water Environment
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• v.20 no.2
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• pp.145-150
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• 2004

This study investigated the effect of chlorine dose and chlorine reaction time for the formation of haloacetic acids (HAAs). According to the results, HAA formation was highly affected by chlorine dose and chlorine reaction time. HAA formation reached a plateau value at 30 mg/L of chlorine dose and 24 hr of chlorine reaction time. For the speciation of formed HAAs in the test water, the concentration of brominated-HAAs was significantly lower than that of chlorinated-HAAs because of low level of bromide ion concentration in the test water. It also investigated the removal efficiency of HAA precursors by several unit processes, such as ozone alone, UV alone, and combined ozone/UV system. Of them, ozone/UV system was proved as the best process to control the HAAs formation. The increase of the brominated-HAAs was observed during ozonation with and without UV irradiation showing the slight increase of total HAA concentrations.