• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.04a
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• pp.82-84
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• 2006

• Environmental Engineering Research
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• v.13 no.1
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• pp.28-32
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• 2008

The photocatalytic treatment of water contaminated with 2,4,6-trinitrotoluene (TNT) was explored in bench-scale experiments in batch mode using a Pyrex tube coated with a thin film of $TiO_2$ located inside a photoreactor. The reactor was aerated by purging it with compressed air before initiating the photocatalytic reaction. The rate of TNT degradation approximated first-order kinetics. The reaction rate constant decreased as the TNT concentration increased from 25 to 100 mg/L, while the first-order kinetics could be modeled using a Langmuir adsorption isotherm. The addition of the organic reductants methanol and EDTA significantly enhanced the rate of TNT degradation, with optimum results in the presence of 20% methanol by volume. EDTA increased the rate of TNT removal by enhancing the role of the reductants.

• The Korean Journal of Ecology
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• v.21 no.3
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• pp.277-282
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• 1998

The microbial degradation of $poly-{\beta}-hydroxybutyrate$ (PHB) films was studied in soil microco는 incubated at a constant temperature of 2, 10, 20, 30 and $40^{\circ}C$ for up to 49 days. The degradation rate measured through loss of weight was enhanced by incubation at a higher temperature. At the soil temperature $40^{\circ}C$, $poly-{\beta}-hydroxybutyrate$ was rapidly degraded at a decay rate of 3.5% weight loss per day. The degradation of $poly-{\beta}-hydroxybutyrate$ did not affected significantly the chemical properties of soils such as pH and electric conductivity. However, microbial activity of soil in terms of dehydrogenase activity was increased by the degradation of $poly-{\beta}-hydroxybutyrate$.

• Journal of Environmental Science International
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• v.13 no.12
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• pp.1059-1065
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• 2004

Bio sparging experiments were conducted in a laboratory column to investigate the potential removal of diesel contaminated groundwater. The objectives in this study were (a) to determine the extent of diesel degradation in laboratory columns under supplement of nutrient; (b) to determine the effect of variation of air flow in the removal of diesel and (c) to evaluate the potential enhancement of diesel degradation as a function of temperature. Our results showed that the nutrient supplement and higher air flow greatly enhanced diesel degradation. However, the variation of water temperature examined slightly increased degradation rate of diesel fuel.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.129-135
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• 1996

In this paper, the hot carrier effect and device degradation of deep submicrometer SC-PMOSFETs have been measured and characterized. It has been shown that the substrate current of a 0.15$\mu$m PMOSFET increases with increasing of impact ionization rate, and the impact ionization rate is a function of the gate length and gate bias voltage. Correlation between gate current and substrate current is investigated within the general framework of the lucky-electron. It is found that the impact ionization rate increases, but the device degradation is not serious with decreasing effective channel length. SCIHE is suggested as the possible phusical mechanism for enhanced impact ionization rate and gate current reduction. Considering the hot carrier induced device degradation, it has been found that the maximum supply voltage is about -2.6V for 0.15$\mu$m PMOSFET.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.323-326
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• 2002

Oxygen uptake characteristics of soil microcosm added by hydrocarbon degrading bacteria screened from polluted site in Korea was studied. The degradation of TPH was enhanced by additon of nononionic surfactants. The amount of oxygen consumed was decreased at higher concentration. The degradation rate of hydrocarbon was decreased by increasing the hydrcarbon concentration.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.360-363
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• 2003

Bioremediation is often used for in situ remediation of petroleum-contaminated site. We studied the microbial degradation of hydrocarbon in an artificially diesel contaminated soil in laboratory microcosm. In control soil, about 30% of the initial TPH was diminished and the degradation of diesel oil was significantly enhanced by the addition of bioremediation agent (70% of TPH reduction).

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.264-265
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• 2014

This Paper reports the photocatalytic activity of $g-C_3N_4/NaTaO_3$ hybrid composite photocatalysts synthesized by ball-mill method. The $g-C_3N_4$ and $NaTaO_3$ were individually prepared by Solid state reaction and microwave hydrothermal process, respectively. The $g-C_3N_4/NaTaO_3$ composite showed the enhanced photocatalytic activity for degradation of rhodamine B dye (Rh. B) under simulated solar light irradiation. The results revealed that the band-gap energy absorption edge of hybrid composite samples was shifted to a longer wavelength as compared to $NaTaO_3$ and the 50 wt% $g-C_3N_4/NaTaO_3$ hybrid composite exhibited the highest percentage (99.6 %) of degradation of Rh. B and the highest reaction rate constant ($0.013min^{-1}$) in 4 h which could be attributed to the enhanced absorption of the hybrid composite photocatalyst in the UV-Vis region. Hence, these results suggest that the $g-C_3N_4/NaTaO_3$ hybrid composite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation in comparison to the commercial $NaTaO_3$.

• Journal of Microbiology and Biotechnology
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• v.11 no.4
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• pp.607-613
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• 2001

The biodegradation rates of diesel oil by a selected diesel-degrading bacterium, Pseudomonas stutzeri strain Y2G1, and microbial consortia composed of combinations of 5 selected diesel-degrading bacterial were determined in liquid and soil systems. The diesel degradation rate by strain Y2G1 linearly increased $(R^2=0.98)$ as the diesel concentration increased up to 12%, and a degradation rate as high as 5.64 g/l/day was obtained. The diesel degradation by strain Y2G1 was significantly affected by several environmental factors, and the optimal conditions for pH, temperature, and moisture content were at pH8, $25^{\circ}C$, and 10%, respectively. In the batch soil microcosm tests, inoculation, especially in the form of a consortium, and the addition of nutrients both significantly enhanced the diesel degradation by a factor of 1.5 and 4, respectively. Aeration of the soil columns effectively accelerated the diesel degradation, and the initial degradation rate was obviously stimulated with the addition of inorganic nutrients. Based on these results, it was concluded that the major rate-limiting factors in the tested diesel-contaminated soil were the presence of inorganic nutrients, oxygen, and diesel-degrading microorganisms. To resolve these limiting parameters, bioremediation strategies were specifically designed for the tested soil, and the successful mitigation of the limiting parameters resulted in an enhancement of the bioremediation efficiency by a factor of 11.

• Advances in nano research
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• v.12 no.4
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• pp.415-426
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• 2022

Nickel substituted cobalt-zinc ferrite nanoparticles with composition Co_0.5Zn_0.5Ni_xFe_2-xO₄ (x = 0.25, 0.5, 0.75, 1.0) were synthesized using a wet chemical method named citrate precursor method. Various characterizations of the prepared nanoferrites were done using X-ray powder diffractometry (XRD), Scanning electron microscopy (SEM), UV visible spectroscopy and Fourier transform spectroscopy technique (FT-IR). XRD confirmed the formation of cubic spinel structure of the samples with single phase having one characteristic peak at (311). The value of optical band gap (E_g) was found to decrease with Ni substitution and have values in the range 2.30eV to 1.69eV. A Fenton-type system was created by photocatalytic activity using source of visible light for removal of methylene blue dye. Observations revealed increase in the degradation of methylene blue dye with increasing nickel content in the samples. The degradation percentage was increased from 77.32% for x = 0.25 to 90.16% for x = 1.0 in one hour under the irradiation of visible light. Also, the degradation process was found to have pseudo first order kinetics model. Hence, it can be observed that synthesized nickel doped cobalt-zinc ferrites have good capability for water purification and its degradation efficiency enhanced with increase in nickel concentration.