• Journal of Industrial Technology
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• v.26 no.A
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• pp.199-205
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• 2006

Ozone alone and catalytic ozone processes were introduced for treatment of humic acid, which is representative refractory organic compound. The treatment efficiencies of humic acid in each process were analyzed in pH variation, DOC removal, and $UV_{254}$ decrease. Mn loaded GAC catalyst was prepared by loading potassium permanganate onto the granular activated carbon surface. BCM-GAC and BCM-Silica gel catalyst were prepared by BCM. $UV_{254}$ decrease in all processes was comparatively high with efficiency over 87%. DOC removal in ozone/GAC process was the highest with 78%, and removal rates for other processes followed the order ozone/BCM-GAC(62%) > ozone/BCM-silica gel(45%) > ozone/silica gel(43%) > ozone/Mn Loaded GAC(42%) > ozone alone(37%).

• Journal of the Korean Society for Heat Treatment
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• v.19 no.5
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• pp.262-269
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• 2006

The development of eco-friendly low pressure carburizing system with high pressure gas quenching(LPC-GQ, 500kg/charge) led to new stage in the fundamental case-hardening treatments. This is due to its ability to provide tighter tolerances on the carburizing process with notable reductions in distortion of the carburized and hardened workpiece. This system is characteristics by high uniformity and reproducibility of heat treatment results, absence of an intergranular oxidation layer, carburizing of complex shapes, reduced cycle time, low operating costs, simplified production, eliminate post washing, and reduced grinding costs.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.156-162
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• 2017

CuO(x)/0.3Al-0.7Ce catalysts with different CuO loadings (x = 2~20 wt%) were prepared by impregnation method and investigated the effects of CuO loadings on the low temperature CO oxidation. Of the used catalysts, the CuO(10)/0.3Al-0.7Ce catalyst showed the highest catalytic performance in the absence or presence of water vapor. In the presence of water vapor, the catalytic performance was drastically decreased, with a temperature of 50% CO conversion ($T_{50%}$) shifted to higher temperature by $50^{\circ}C$ compared to the those in dry conditions because of the competitive adsorption of water vapor on the active sites. The copper metal surface area calculated from $N_2O$-titration analysis and the oxygen capacity from CO-pulse experiments were increased with the CuO loadings and showed a maximum at 10 wt%CuO/0.3Al-0.7Ce catalyst. These trends are in good agreement with the tendency of $T_{50%}$ of the catalysts. From these characteristic aspects, it could be deduced that the catalytic performance was closely related to the oxygen capacity and the copper metallic surface area.

• Journal of Power System Engineering
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• v.8 no.3
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• pp.30-35
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• 2004

In the steel making industries, the continuous casting process has been applied to the number of company because of its economical benefit. Casting rolls are utilized for frictional drive and transport of solidifying slap. Dimensional tolerances, mechanical stability and surface condition of the cast roll can affect both the surface and internal quality of the product being cast. To overcome these problems, the industry is accelerating on the rate of technology improvements. Samples were overlaid on the S45C steel by submerged arc welding process. And the hardness, wear, electrochemical corrosion and oxidation tests were carried out. Test results were that all these materials were satisfying basic requirements of caster rolls. By these results, the addition of 0.1%Nb and 0.15%V increase mechanical properties and tempering resistance by its superior carbide forming characteristics in low carbon $12{\sim}13%Cr$ martensitic stainless steels.

• Environmental Engineering Research
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• v.24 no.2
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• pp.339-346
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• 2019

In this research, applicability of electrochemical technology in removing nitrogenous compounds from solid waste landfill leachate was examined. Novel cathode material was developed at laboratory by introducing a Cu layer on Al substrate (Cu/Al). Al and mild steel (MS) anodes were investigated for the efficiency in removing nitrogenous compounds from actual leachate samples collected from two open dump sites. Al anode showed better performances due to the effect of better electrocoagulation at Al surface compared to that at MS anode surface. Efficiency studies were carried out at a current density of $20mA/cm^2$ and at reaction duration of 6 h. Efficiency of removing nitrate-N using Al anode and developed Cu/Al cathode was around 90%. However, for raw leachate, total nitrogen (TN) removal efficiency was only around 30%. This is due to low ammonium-N removal as a result of low oxidation ability of Al. In addition to the removal of nitrogenous compounds, reactor showed about 30% removal of total organic carbon. Subsequently, raw leachate was diluted four times, to simulate pre-treated leachate. The diluted leachate was treated and around 88% removal of TN was achieved. Therefore, it can be said that the reactor would be good as a secondary or tertiary treatment step in a leachate treatment plant.

• Environmental Engineering Research
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• v.25 no.4
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• pp.579-587
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• 2020

Novel silane grafted bentonite was obtained using the natural bentonite as precursor material. The material which is termed as nanocomposite was characterized by the Fourier Transform Infra-red (FT-IR) and X-ray diffraction (XRD) methods. The surface imaging and elemental mapping was performed using Scanning Electron Microscopic (SEM/EDX) technique. The electroanalytical studies were performed using the nanocomposite electrode. The electroactive surface area of nanocomposite electrode was significantly increased than the pristine bentonite or bare carbon paste based working electrode. The impedance spectroscopic studies were conducted to simulate the equivalent circuit and Nyquist plots were drawn for the carbon paste electrode and nanocomposite electrodes. A single step oxidation/reduction process occurred for As(III) having ΔE value 0.36 V at pH 2.0. The anodic stripping voltammetry was performed for concentration dependence studies of As(III) (0.5 to 20.0 ㎍/L) and reasonably a good linear relationship was obtained. The detection limit of the As(III) detection was calculated as 0.00360±0.00002 ㎍/L having with observed relative standard deviations (RSD) less than 4%. The presence of several cations and anions has not affected the detection of As(III) however, the presence of Cu(II) and Mn(II) affected the detection of As(III). The selectivity of As(III) was achieved using the Tlawng river water sample spiked with As(III).

• Analytical Science and Technology
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• v.10 no.4
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• pp.264-273
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• 1997

Anodic oxidation reaction was applied to remove trihalomethanes in an aqueous solution. Each component was determined by using solid phase microextraction(SPME) fiber and GC-ECD. Anodic and cathodic compartments were separated in order to protect contaminants and connected by $KNO_3$-agar bridge. The calibration graphs of the 6 THM components were shown good linearlity from a few ppb up to a few hundreds ppb concentration level. Anodes such as platinum(Pt), titanium(Ti). zircornium(Zr), titanium metal coated with iridium(Ti-Ir), and glassy carbon coated with mixed valence ruthenium(mv Ru) were tried to remove the THMs at different potentials. The best result was obtained on the Ti-Ir anode applied 9 volts DC. The electrode could effectively remove almost all the THM components from the stirring solution within about 1.5 hours. The glassy carbon electrode coated with mixed valence ruthenium showed excellent removing effect at the begining, but the maximum removing level was remained at 60% probably due to the destruction of the electrode surface. The concentration of chloroform, however, tends to be increased due to the electrode reaction producing the component at the condition.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.562-562
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• 2012

Recently, graphene and graphene-based materials such as graphene oxide (GO) or reduced graphene oxide (R-GO) draws a great attention for electronic devices due to their structures of one atomic layer of carbon hexagon that have excellent mechanical, electrical, thermal, optical properties and very high specific surface area that can be high potential for chemical functionalization. R-GO is a promising candidate because it can be prepared with low-cost from solution process by chemical oxidation and exfoliation using strong acids and oxidants to produce graphene oxide (GO) and its subsequent reduction. R-GO has been used as semiconductor or conductor materials as well as sensing layer for bio-molecules or ions. In this work, reduced graphene oxide field-effect transistor (R-GO FET) has been fabricated with ITO extended gate structure that has sensing area on ITO extended gate part. R-GO FET device was encapsulated by tetratetracontane (TTC) layer using thermal evaporation. A thermal annealing process was carried out at $140^{\circ}C$ for 4 hours in the same thermal vacuum chamber to remove defects in R-GO film before deposition of TTC at $50^{\circ}C$ with thickness of 200 nm. As a result of this process, R-GO FET device has a very high stability and durability for months to serve as a transducer for sensing applications.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.1
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• pp.1-13
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• 2012

We measured various geochemical parameters, including the grain size, loss on ignition(LOI), total organic carbon(TOC), total nitrogen(TN), total sulfur(TS) and metallic elements, in surface sediment collected from 19 stations in Gamak Bay in April 2010 in order to understand the sedimentary types, the origin of organic matters, and the distribution patterns of alkali(Li, Na, K, Rb) and alkaline earth(Be, Mg, Ca, Sr, Ba) elements. The surface sediments were mainly composed of mud. The concentrations of Chlorophyll-a, TOC, TN, TS and LOI in sediment were the highest at the cultivation areas of fish and shellfish in the northern and southern parts of the bay. The redox potential(or oxidation-reduction potential) showed the positive value in the middle part of the bay, indicating that the surface sediment is under oxidized condition. The organic materials in sediment at almost all of stations were characterized by the autochthonous origin. Based on the overall distributions of metallic elements, it appears that the concentrations of alkali and alkaline earth elements except Ba in sediment are mainly influenced by the dilution effect of quartz. The concentrations of Sr and Ba are also dependent on the secondary factors such as the effect of calcium carbonate and the redox potential.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1280-1286
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• 2006

Three different virgin activated carbons made of each coal(Calgon), coconut(Samchully) and wood(Picabiol) based activated carbon(AC) were tested for an adsorption performance of 1,4-dioxane in a continuous adsorption column. Breakthrough behavior was Investigated that the breakthrough points of coal, coconut and wood based AC were observed as 3600 bed volumn(BV), 1440 BV and 144 BV respectively. Adsorption capacity(X/M) of coal, coconut and wood based AC was observed. The reported results of adsorption capacity showed that coal based AC was highest(578.9 ${\mu}g/g$), coconut based AC was intermediate(142.3 ${\mu}g/g$) and wood based AC was lowest(7.4 ${\mu}g/g$) due to increasing specific surface area. Moreover, carbon usage rates(CURs) for coal, coconut and wood based AC had been shown as 0.48 g/day, 1.41 g/day and 6.9 g/day respectively. The constant characteristic of the system, k of coal based AC was found to be 91.5 and k of coconut based AC was found to be 17.9. Removal efficiencies of 1,4-dioxane with different ozonation dosages(2 and 5 mg/L) for 20 min ozonation had been shown 38% and 87% respectively. There was no observation for biological removal of 1.4-dioxane by attached micro-organisms when used(3.1 years and over 5 years) biological activated carbon(BAC) without pretreatment of oxidation were employed. When a combination of ozonation(2 mg/L and 5 mg/L) and BAC process for $10{\sim}30$ min was applied, removal efficiency for 1,4-dioxine increased only $2{\sim}6%$ compared to only applying ozonation. Therefore removal efficiency of BAC process prior to using oxidation was proven to negligible. Consequently, the results presented in this paper provide a better insight into the adsorption performance of 1,4-dioxane. This observation suggests that using virgin activated carbon made of coal is the best selection for removal of 1,4-dioxane in the water treatment for an advanced treatment. It is clear from this research that longer EBCT for ozonation or higher ozone concentration are more effective operation methods for removal of 1,4-dioxane than longer EBCT in the BAC process.