• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1825-1832
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• 2000

Column experiments were conducted by using soil columns, to investigate feasibility and efficiency of in-situ ozone enhanced remediation for diesel-contaminated soil. The injection of gaseous ozone into soil column revealed the enhanced decomposition of ozone due to the catalytic reaction between ozone and metal (e.g., Fe, Mn etc.) oxides as evidenced by as much as 25 times shorter half-life of ozone in a sand packed column than in a glass beads packed column. Substantial retardation in the transport of and the consumption of ozone were observed in the diesel contaminated field soil and sand packed columns. After 16 hrs ozonation, 80% of the initial mass of diesel (as diesel range organic) concentration of $800{\pm}50mg/kg$, was removed under the conditions of the flow rate of 50mL/min and $6mg-O_3/min$. Whereas, less than 30% of diesel was removed in the case of air injection. Analysis of the residual TPH(total petroleum hydrocarbon) and selected 8 aliphatics of diesel compounds in the inlet and the outlet of the column confirmed that diesel nonselectively reacted with ozone and then shifted to lower carbon numbered molecules. Water content also was found to be an important parameter in employing ozone to the hydrocarbon-contaminated soil.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.1-10
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• 2005

The purpose of this study was to evaluate the potential of a gamma irradiation to decompose 2,4,6-trinitrotoluene(TNT) in an aqueous solution. The decomposition reaction of TNT by gamma irradiation was a pseudo first-order kinetic over the applied initial concentrations($25{\sim}100mg/L$). The dose constant was strongly dependent on the initial TNT concentration. The removal of TNT was more efficient at pH below 3 and at pH above 11 than at neutral pH(pH 5-9). The required irradiation dose to remove over 99% of TNT was 40, 80 and 10 kGy, individually at pH 2, 7 and 13. The dose constant was increased by 1.6 fold and over 15.6 fold at pH 2 and 13, respectively, when compared with that at pH 7 When irradiation dose of 200 kGy was applied, the removal efficiencies of TOC were 91, 46 and 53% at pH 2, 7 and 13, respectively. Ammonia and nitrate were detected as the main nitrogen byproducts of TNT and glyoxalic acid and oxalic acid were detected as organic byproducts. The results showed that a gamma irradiation was an attractive method for the decomposition of TNT in an aqueous solution. However, regarding the application of high energy radiation for the TNT decomposition and mineralization, an application of an acidic pH below 3 to the solution before irradiation should be considered.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.4
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• pp.380-391
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• 1993

The experimental study was made to propose the treatment method of wastewater in the high-density fish culture system. The BOD to COD ratios of effluents were almost same to 0.65 in the eel-farm, but were various in the farm rearing together with tilapia etc. A BOD rate curve of the eel-farm effluent could be described mathematically by the equation, $BODu=14.1(1-10^{-0.222t})+30.9(1-10^{-0.035(t-8)})$. Nitrification in Biological Fluidized Bed(BFB) system to treat the fish-farm wastewater could be reduce ammonium level up to $65{\sim}79\%$ when ammonium loading rates were between 0.014 and 0.075g $NH_4/g$ BVS-day. Nitrification efficiency was decreased by organic matters in the wastewater when ammonium loading was low(0.014 g $NH_4/g$ BVS-day). T-N removal ratios were decreased to increase loading in denitrification process, because of low C/N ratio. Based on much higher biological mass concentrations, BFB system takes many advantages of a practical viewpoint, such as stability of treatment efficiency and reduction of necessary site area for the facility, as compared with conventional treatment systems.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.79-89
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• 2009

Naphthalene is a volatile, hydrophobic, and possibly carcinogenic compound that is known to have a severe detrimental effect to aquatic ecosystem. Our research examined the effects of various operating conditions (temperature, pH, initial concentration, and frequency and type of ultrasound) on the sonochemical degradation of naphthalene and OH radical production. The MDL (Method detection limit) determined by LC/FLD (1200 series, Agilient) using C-18 reversed column is measured up to 0.01 ppm. Naphthalene vapor produced from ultrasound irradiation was detected under 0.05 ppm. Comparison of naphthalene sonodegradion efficiency tested under open and closed reactor cover fell within less than 1% of difference. Increasing the reaction temperature from $15^{\circ}C$ to $40^{\circ}C$ resulted in reduction of naphthalene degradation efficiency ($15^{\circ}C$: 95% ${\rightarrow}$ $40^{\circ}C$: 85%), and altering pH from 12 to 3 increased the effect (pH 12: 84% ${\rightarrow}$pH 3: 95.6%). Pseudo first-order constants ($k_1$) of sonodegradation of naphthalene decreased as initial concentration of naphthalene increased (2.5 ppm: $27.3{\times}10^{-3}\;min^{-3}\;{\rightarrow}$ 10 ppm : $19.3{\times}10^{-3}\;min^{-3}$). Degradation efficiency of 2.5 ppm of naphthalene subjected to 28 kHz of ultrasonic irradiation was found to be 1.46 times as much as when exposed under 132 kHz (132 kHz: 56%, 28 kHz: 82.7%). Additionally, its $k_1$ constant was increased by 2.3 times (132 kHz: $2.4{\times}10^{-3}\;min^{-1}$, 28 kHz: $5.0{\times}10^{-3}\;min^{-1}$). $H_2O_2$ concentration measured 10 minutes after the exposure to 132 kHz of ultrasound, when compared with the measurement under frequency of 28 kHz, was 7.2 times as much. The concentration measured after 90 minutes, however, showed the difference of only 10%. (concentration of $H_2O_2$ under 28 kHz being 1.1 times greater than that under 132 kHz.) The $H_2O_2$ concentration resulting from 2.5 ppm naphthalene after 90 minutes of sonication at 24 kHz and 132 kHz were lower by 0.05 and 0.1 ppm, respectively, than the concentration measured from the irradiated M.Q. water (no naphthalene added.) Degradation efficiency of horn type (24 kHz) and bath type (28 kHz) ultrasound was found to be 87% and 82.7%, respectively, and $k_1$ was calculated into $22.8{\times}10^{-3}\;min^{-1}$ and $18.7{\times}10^{-3}\;min^{-1}$ respectively. Using the multi- frequency and mixed type of ultrasound system (28 kHz bath type + 24 kHz horn type) simultaneously resulted in combined efficiency of 88.1%, while $H_2O_2$ concentration increased 3.5 times (28 kHz + 24 kHz: 2.37 ppm, 24 kHz: 0.7 ppm.) Therefore, the multi-frequency and mixed type of ultrasound system procedure might be most effectively used for removing the substances that are easily oxidized by the OH radical.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.565-574
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• 1993

The Ar/Ar- $H_{2}$ plasma method Lvas applied to reduce and refine high purity Nb metal. Inaddition, the reaction between molten Nb metal and hydrogen were also analyzed in the Ar-(20%)$H_{2}$plasma. The metallic Nb of 99.5wt% was obtained at the ratio of $C/Nb_{2}O_{5}$=5.00 in the Ar plasma reductionand the $O_2$ loss from the thermal decomposition of niobium oxides did not take place. In the Ar-(20%)Hi plasma the metallic Nb of 99.8wt% was produced at the ratio of $C/Nb_{2}O_{5}$=4.80. It was observedthat a major reaction of the deoxidation was the reaction with H, Hi, and a deoxidation by the evaporationof $NbO_x$ did not occur but a mass loss of Nb did by a "splash" effect. The deoxidation reaction rateobeyed the 1st order reaction kinetics and the reaction rate constant(k') of deoxidation was $7.8 \times 10_{-7}$(m/sec).The solubility of hydrogen in Nb metal was 60ppm and it was larger than the solubility of molecularstate hydrogen by 40ppm in the Ar-(20%)$H_{2}$ plasma method. A saturation was within 60sec anda hydrogen content was reduced below lOppm by a Ar plasma re-treatment.by a Ar plasma re-treatment.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.495-504
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• 2015

This work investigated the characteristics of a packed-bed plasma reactor system and the performances of the plasma reactors connected in series or in parallel for the decomposition of ethylene. Before the discharge ignition, the effective capacitance of the ${\gamma}$-alumina packed-bed plasma reactor was larger than that of the reactor without any packing, but after the ignition the effective capacitance was similar to each other, regardless of the packing. The energy of electrons created by plasma depends mainly on the electric field intensity, and was not significantly affected by the gas composition in the range of 0~20% (v/v) oxygen (nitrogen : 80~100% (v/v)). Among the various reactive species generated by plasma, ground-state atomic oxygen and ozone are understood to be primarily involved in oxidation reactions, and as the electric field intensity increases, the amount of ground-state atomic oxygen relatively decreases while that of nitrogen atom increases. Even though there are many parameters affecting the performance of the plasma reactor such as a voltage, discharge power, gas flow rate and residence time, all parameters can be integrated into a single parameter, namely, specific input energy (SIE). It was experimentally confirmed that the performances of the plasma reactors connected in series or in parallel could be treated as a function of SIE alone, which simplifies the scale-up design procedure. Besides, the ethylene decomposition results can be predicted by the calculation using the rate constant expressed as a function of SIE.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.737-742
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• 1999

This study was conducted for the two purposes; one was removal of dissolved humic acid, the well-known precursor of trihalomethanes (THMs), by physicochemical treatment processes such as ozone oxidation, coagulation and activated carbon adsorption. The other was qualitative identification of by-products in chlorination of the dissolved humic acid. When ozone oxidation was applied to remove the dissolved humic acid, pH was abruptly decreased. It was indicated that humic acid was not perfectly converted to $CO_2$ and $H_2O$, but to low fatty acid. In coagulation process, the coagulant was polyaluminumchloride which was widely used for drinking water treatment in recent years. With the dosage of 160 mg/L, total organic carbon(TOC), $COD_{Cr}$ and color were removed with 23%, 24% and 5% respectively. Color was effectively removed by ozone oxidation process, which was the first order reaction, with the reaction rate constant of $0.067min^{-1}$. In activated carbon adsorption process, preozonation process could remove more effectively the dissolved humic acid than that without preozonation. When the dissolved humic acid and sodium hydrochloride were reacted with 1 mg-NaOCl/mg-TOC, only trihalomethanes were detected.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.844-851
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• 2005

The purpose of this study was to determine feasibility of application of regenerated or recycled $TiO_2$ on the successive treatment of Cu(II)-EDTA. The recovery of copper, the reuse of $TiO_2$ and the assessment of acute toxicity was studied in the total eight successive photocatalytic reactions. Aqueous solution of $10^{-4}\;M$ Cu(II)-EDTA was treated using an illuminated $TiO_2$ at pH 6 in a circulating reactor. Two different procedures were applied in the reuse of $TiO_2$: i) recycle of $TiO_2$ without acid wash ii) regeneration of $TiO_2$ with acid wash to remove adsorbed copper in a previous experiment. The averaged decomplexation rate constant($k'_{obs}$) of Cu(II)-EDTA in recycle of $TiO_2$ without acid wash was approximately 45% less than that in regeneration of $TiO_2$ with acid wash. Removal of Cu(II) was near complete after 180 minutes in the total eight successive photocatalytic reactions using the regenerated $TiO_2$ after acid wash. In contrast, removal of Cu(II) was minimum at total fifth successive photocatalytic oxidation using the recycled $TiO_2$ without arid wash. The recovered $TiO_2$ was approximately 86% in average in each procedure. The recovered Cu(II) was 67.9% in average. The acute relative toxicity of the treated water rapidly declined at an initial reaction time up to 60 minutes but little declination was observed after 60 minutes due to little degradation of DOC. Relative toxicity of treated water using the recycled $TiO_2$ without acid wash we some what well correlated with the concentration of dissolved Cu(II). From this work, it is suggested that Cu(II)-EDTA can be effectively treated using an integrated cyclic photocatalytic oxidation with recovery of $TiO_2$ and Cu(II).