• Journal of the Mineralogical Society of Korea
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• v.27 no.2
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• pp.97-105
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• 2014

Artificial precipitation ponds, consisting of three steps of oxidation pond, successive alkalinity producing system (SAPS) and swamp, were constructed for the treatment of the acid mine drainage from the Iwal coal mine. The efficacies of the passive treatment system in terms of neutralization of mine water and removal of dissolved ions were evaluated by the chemical analyses of the water samples. Mine water in the mine adits was acidic, showing the pH value of 2.28-2.42 but the value increased rapidly to 6.17-6.53 in the Oxidation pond. The purification efficiencies for the removal of Al and Fe were 100%, whereas those of $SO_4$, Mg, Ca, and Mn were relatively low of 50%, 40%, 24%, and 59%, respectively. These results indicate a need for application of additional remediation techniques in the passive treatment systems. The precipitates that formed at the bottom of the mine water channels were mainly schwertmannite ($Fe_8O_8(OH)_6SO_4$) and those in the leachate water were 2-line ferrihydrite ($Fe_2O_3{cdot}0.5H_2O$).

• Journal of Korean Society of Environmental Engineers
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• v.38 no.8
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• pp.411-419
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• 2016

The objective of this study was to evaluate the application possibility of tube type electrolysis module system using recirculation process through removal organic matters and nitrogen in the pigment wastewater. The tube type electrolysis module consisted of a inner rod anode and an outer tube cathode. Material used for anode was titanium electroplated with $RuO_2$. Stainless steel was used for cathode. It was observed that the pollutant removal efficiency was increased according to the decrease of flowrate and increase of current density. When the retention time in tube type electrolysis module system was 180 min, chlorate concentration was 382.4~519.6 mg/L. The chlorate production was one of the major factors in electrochemical oxidation of tube type electrolysis module system using recirculation process used in this research. The pollutant removal efficiencies from the bench scale tube type electrolysis module system using recirculation operated under the electric charge of $4,500C/dm^2$ showed the $COD_{Mn}$ 89.6%, $COD_{Cr}$ 67.8%, T-N 96.8%, and Color 74.2%, respectively and energy consumption was $5.18kWh/m^3$.

• Clean Technology
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• v.19 no.3
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• pp.320-326
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• 2013

Nano-sized PtRu-Ni/VC and PtRu-Sn/VC electrocatalysts were synthesized by a one-step radiation-induced reduction (RIR) (30 kGy) process using distilled water as the solvent and Vulcan XC-72 as the supporting material. The obtained electrocatalysts were characterized by transmission electron microscopy (TEM), scanning electron microscope energy dispersive spectroscopic (SEM-EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The catalytic efficiency of electrocatalysts was examined for oxygen reduction, MeOH oxidation and CO stripping decreased in the following order, Hydrogen stripping : PtRu-Sn/VC > PtRu-Ni/VC > PtRu/VC$^{(R)}$ (E-TEK). MeOH oxidation : PtRu-Sn/VC > PtRu-Ni/VC > PtRu/ VC$^{(R)}$ (E-TEK). Unit cell performance : PtRu-Sn/VC > PtRu-Ni/VC > PtRu/VC$^{(R)}$ (E-TEK) catalysts.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.22-27
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• 2018

In this study, the effect of physical properties of $Pt/TiO_2$ on $NH_3$-selective catalytic oxidation (SCO) reaction at $200{\sim}350^{\circ}C$ was investigated. CO-chemisoption and BET analysis were carried out to verify physical properties of $Pt/TiO_2$. By characterizing physical properties of $Pt/TiO_2$ with respect to the Pt loading, the metal dispersion degree decreased as a function of the Pt loading amount. Also, the catalyst having a higher metal dispersion showed an excellent conversion efficiency of $NH_3$ to $N_2$. Since the specific surface area of the support affects the metal dispersion, $Pt/TiO_2$ catalysts were prepared using $TiO_2$ with different physical properties. As a result, it was confirmed that the catalyst having a wide specific surface area exhibited a excellent conversion of $NH_3$ to $N_2$.

• Journal of Korea Soil Environment Society
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• v.2 no.3
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• pp.49-57
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• 1997

Naturally-occurring iron minerals, goethite and magnetite, were used to catalyze hydrogen peroxide and initiate Fenton-like oxidation of silica sand contaminated with diesel, kerosene in batch systems. Reaction conditions were investigated by varying H$_2$0$_2$concentration(0%, 1%, 15%), initial contaminant concentration(0.2, 0.5, 1.0g diesel and kerosene/kg soil), and iron minerals(1, 5wt% magnetite or goethite). Contaminant degradations in silica sand-iron mineral-$H_2O$$_2$ systems were identified by determining total petroleum hydrocarbon(TPH) concentration. In case of silica sand contaminated with diesel(1g contaminan/kg soil with 5wt% magnetite) addition of 0%, 1%, 15% of $H_2O$$_2$showed 0%, 25%, and 60% of TPH reduction in 8 days, respectively When the mineral contents were varied from 1 to 5wt%, removal of contaminants increased by 16% for magnetite and 13.1% for goethite. The results from system contaminated by kerosene were similar to those of the diesel. Reaction of magnetite system was more aggressive than that of goethite system due to dissolution of iron and presence of iron(II) and iron(III); however, dissolved iron precipitated on the surface of iron mineral and seemed to cause reducing electron transfer activity on the surface and quenching $H_2$$O_2$. The system used goethite has better treatment efficiency due to less $H_2$$O_2$ consumption. Results of this study showed possible application of catalyzed $H_2$$O_2$ system to petroleum contaminated site without addition of iron source since natural soils generally contain iron minerals such as magnetite and goethite.

• Journal of Soil and Groundwater Environment
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• v.15 no.2
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• pp.10-17
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• 2010

Advanced oxidation processes (AOPs) have advantages to reduce the processing time and mineralize contaminants dissolved in groundwater. Recently, remediation techniques for organic contamination in groundwater have been studied, and technology using $UV/H_2O_2$ is generally accepted as one of the most powerful and reliable alternative for the remediation of groundwater contamination. In this study, $UV/H_2O_2$ technology, which generates hydroxyl radical ($\cdot$ OH) as known for strong non-selective oxidant, was used to degrade chlorinated solvents (TCE and PCE), and it was expanded to apply continuous stirred tank reactor (CSTR) system (i.e. combinations of three CSTR). The tested parameters for CSTR system were retention time and groundwater/$H_2O_2$ injection volume ratio. To find optimum parameters for CSTR system, various retention time (6 min ~ 90 min) and groundwater/$H_2O_2$ injection volume ratio (5/1 ~ 119/1) were tested. Other conditions for CSTR were adapted from the batch test results, which concentration of $H_2O_2$ and UV dose were 29.4 mM (0.1%) and 4.3 kWh/L, respectively. Based on the experimental results, the optimum parameters for CSTR system were 20 min for retention time and 119/1 for groundwater/$H_2O_2$ injection volume ratio. Applying these optimum conditions, chlorinated solvents (TCE and PCE) were removed at 99.9% and 99.6%. Moreover, the effluent concentrations of TCE and PCE are 0.036 mg/L and 0.087 mg/L, respectively, which are satisfied the regulatory level (TCE 0.3 mg/L, PCE 0.1 mg/L). Consequently, the CSTR system using $UV/H_2O_2$ technology can achieve high removal efficiency in the event of treatment of groundwater contaminated by chlorinated solvents (TCE and PCE).

• Korean Journal of Microbiology
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• v.43 no.2
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• pp.130-136
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• 2007

Natural 6-dodecen-4-olide (Butte lactone) was produced from plant oils containing high unsaturated fatty acids via two-stage microbial hiotransformation. After unsaturated fatty acids were liberated from plant oil by microbial lipase, these were converted to optically active hydroxyl fatty acid (HFA) by hydroxylation reaction of Pseudomonas sp. NRRLB-2994. When safflower oil containing >75% unsaturated fatty acid, linoleoic acid wasused, Pseudomonas sp. produced 8g/L of 10-hydroxy-12(z)-octadecanoicacid with average of 39.2% bioconversion efficiency during 48 hr biotransformation period. The recovered 10-hydroxy-12-octadecanoic acid was further bioconverted to 4-hydroxy-6-dodecenoic acid via partial ${\beta}-oxidation$ by Yarriowia lipolytica ATCC34088. 4-hydroxy-6-dodecenoic acid in culture was lactonized by lowering pH to 4.0 using $4N\;H_{2}SO_{4}$ and heating for 5 min to 6-dodecen-4-olide (Butter lactone). Natural 6-dodecen-4-olide had characteristic aroma properties when compared to 6-dodecan-4-oilde (dodecalactone) and 4-decen-4-olide (decalactone).

• Microbiology and Biotechnology Letters
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• v.34 no.3
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• pp.257-264
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• 2006

An aerobic submerged membrane bioreactor (MBR) treating ammonium wastewater was studied in respect of nitrification characteristics and distribution of nitrification bacteria over a period of 350 days. MBR was fed with ammonium concentration of 500-1000 mg $NH_4-N/L$ at a nitrogen load of $1-2kg\;N/m^3{\cdot}d$. Overall ammonium oxidation rate increased with dissolved oxygen (DO) concentration, temperature, and sludge retention time (SRT). Under a higher concentration of free ammonia ($NH_3-N$) due to the decrease of ammonium oxidation rate, the nitrite ratio ($NO_2-N/NO_x-N$) in the effluent increased. The sudden collapse of nitrification efficiency accompanied by sludge foaming and the increase of sludge volume index (SVI) was observed unexpectedly during the operation. At the later stage of operation, additional carbon source was fed to the MBR and resulted in twice higher value of SVI and the decrease of ammonium oxidation rate. In fluorescence in situ hybridization (FISH) analysis, genus Nitrosomonas which is specifically hybridized with probe NSM156 was initially the dominant ammonia oxidizing bacteria and the amount of Nitrosospira gradually increased. Nitrospira was the dominant nitrite oxidizing bacteria during whole operational period. Significant amount of Nitrobacter was also detected which might due to the high concentration of nitrite maintained in the reactor.

• Ecology and Resilient Infrastructure
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• v.1 no.1
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• pp.19-24
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• 2014

The research evaluates the possibility of generating electricity using pyrite containing mine tailings, which are the major cause of acid mine drainage (AMD), by applying iron oxidizing bacteria (in this case, Acidithiobacillus ferrooxidans) and chemical fuel cell technology. The changes in the aqueous $Fe^{2+}$ concentration, which can represent an ionized form of pyrite, with an initial concentration of 9,000 mg/L were investigated during the 20 d growth period. Both the $Fe^{2+}$ and total iron (i.e., total $Fe^{2+}$)concentrations with or without A. ferrooxidans were observed. The $Fe^{2+}$ concentration decreased to about 6,000 mg/L, in the abiotic condition, while it decreased to about 400 mg/L in the biotic condition. The results showed that the increased $Fe^{2+}$ oxidation in the presence of A. ferrooxidans (i.e., catalytic ability of A. ferrooxidans) can be applied to electricity generation using pyrite containing mine tailings. In the co-presence of A. ferrooxidans and pyrite containing mine tailings, $Fe^{2+}$ oxidation and hence electron production increases, which, in turn, improves current density. This study can be applied to utilize ecological functions of indigenous bacteria in mine areas to enhance electricity generation efficiency.

• Korean Journal of Environmental Agriculture
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• v.24 no.3
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• pp.203-209
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• 2005

Objective of this research was to assess the effectiveness of the different sources of the zero-valent irons (ZVIs) on the reduction of the toxic Cr(VI) to the nonhazardous Cr(III) in an aqueous solution. The physical and chemical properties of the six ZVIs were determined. Particle size and specific surface area of the ZVIs were in the ranges of $85.55{\sim}196.46{\mu}m\;and\;0.055{\sim}0.091m^2/g$, respectively. Most of the ZVIs contained Fe greater than 98% except for J (93%) and PU (88%). Reduction efficiencies of the ZVI for Cr(VI) reduction were varied with kinds of ZVIs. The J and PU ZVIs reduced 100% and 98% of Cr(VI) in the aqueous solution, respectively, within 3 hrs of reaction. However, PA, F, Sand J1 reduced 74, 65, 29 and 11% of Cr(VI), respectively, after 48 hrs. The pH of the reacting solution was rapidly increased from 3 to $4.34{\sim}9.04$ within 3 hrs. The oxidation-reduction potential (Eh) of the reacting solution was dropped from 600 to 319 mV within 3 hrs following addition of ZVIs to the Cr(VI) contaminated water. The capability of ZVIs for Cr(VI) reduction was the orders of PU > J > PA > F > S > J1, which coincided with the capacities to increase the pH and decrease the redox potentials. Results suggested that the reduction of Cr(VI) to Cr(III) was derived from the oxidation of the ZVI in the aqueous solution.