• Korean Journal of Soil Science and Fertilizer
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• v.39 no.3
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• pp.157-162
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• 2006

Objective of this research was to evaluate optimal conditions of arsenic adsorption in water by zero-valent iron (ZVI). Batch experiment showed that adsorption of arsenic by ZVI followed a Langmuir isotherm model. The masses of As(V) adsorbed onto ZVI were increased as decreasing pH of the reacting solution (pH 3: 2.05, pH 5: 1.82, pH 7: 1.24, pH 9: 1.03 mg As/g $Fe^0$) and as increasing the temperature ($15^{\circ}C$ : 1.59, $25^{\circ}C$ : 1.81, 35 : $1.93^{\circ}C$ mg As/g $Fe^0$). The SEM and EDS (energy dispersive X-ray spectrometer) analysis of morphology and structure of ZVI before and after reacting with arsenic in water revealed that a relatively smooth and large surface of ZVI was transformed into a coarse and small surface particle after the reaction. The EDS spectra on the chemical composition of ZVI demonstrated that arsenic was incorporated into ZVI by adsorption mechanism. The XRD analysis also identified that the only peak for $Fe^0$ in the ZVI before the reaction and confirmed that $Fe^0$ was transformed into $Fe_2O_3$ and FeOOH, and As into $FeAsO_4{\cdot}2H_2O$.

• Economic and Environmental Geology
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• v.40 no.2 s.183
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• pp.141-151
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• 2007

This study was focused on iron removal from illite by L-ascorbic and oxalic acids. Iron has been shown as a secondary mineral such as iron oxides and hydroxides in illite ores. It is also known as a primary agent to degrade brightness index of the ores. Methods such as physical separation and chemical leaching with strong inorganic acids have been widely used to remove the iron from the ores. However, these methods are expensive and give rise to environmental problems. In this study, we examined an alternative method using solutions with different set of combination of sulfuric, hydrochloric, L-ascorbic, and oxalic acids. Compared to chemical treatments with only inorganic acids, our results demonstrate that an addition of L-ascorbic acid in inorganic acids results in decreasing both total concentrations of the inorganic acids and time for the treatments. The treatment with 0.15 M L-ascorbic acid and 0.25 M sulfuric acid in solution for 60 min significantly improved the brightness index from 42.4% to 74.4%. This improvement is similar to that of treatment with only 2.5 M sulfuric acid alone for 150 min. Mineralogical and chemical analyses were performed to compare the effect of acid leaching on illite powders. No obvious differences are observed in the mineralogical characteristics and particle size distributions of the samples. These results suggest that the treatment with the addition of L-ascorbic acid in sulfuric acid could effectively remove iron without modifying the physicochemical properties of illite under conditions used in this study.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.207-212
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• 2008

This study focused on shorten the period of the struvite crystal birth and development by adding seed materials. For this purpose, three different seed materials were selected: sand, anthracite and struvite. The experiments has been conducted to evaluate the effect of the particle size of the selected seed material on the struvite crystallization, and to study the mixing effect which can be expressed by the value of $G{\cdot}t_d$(the multiple of mean velocity gradient(G) and mixing time($t_d$)). It was observed in this study that the removal efficiency of ammonia nitrogen increased by 9%, 11%, and 20% for sand, anthracite, and struvite added as the seed material, respectivley. This indicated that the struvite crystallization efficiency had a close correlation with the specific surface area of the seed particle. It was found that when struvite was selected as the seed material, the struvite crystallization proceeded at lower $G{\cdot}t_d$ value as compared with other seed materials. This observation implied that the secondary crystal birth would be dominated in this reaction. It was concluded in this study that the particle size was not significant factor on the struvite crystallization, while the $G{\cdot}t_d$ value was a considerably important factor in terms of the theory of the struvite crystal birth.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.257-268
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• 2003

Daily monitoring was conducted to elucidate the changes in turbidity and distribution of particles in the turbid water of a river-type reservoir (Paltang Reservoir) from 1999 to 2001. Water turbidity and the particle distribution of turbid water were principally affected by meteorological factors particularly rainfall patterns and hydrological factors such as inflow and outflow. The mean concentration of turbidity was constant each year, with the concentration of less than 10 NTU accounting for 85%. Seasonal characteristics were remarkable, with winter and spring having < 5 NTU, autumn 5 ${\sim}$ 10 NTU, and summer > 20 NTU. Unlike hydrological changes, maximum turbidity was observed from late July to early August and continuously increased from 1999 to 2001. In particular, the maximum turbidity of reservoirs remarkably increased toward the lower part of reservoir in 2001. Discharge and turbidity increased or decreased slowly in 1999; in contrast, turbidity rapidly increased in the early rainfall period of 2000 and 2001 but later decreased as discharge increased. In the particles of turbid water, clay ingredients were more densely distributed and more dominant in all stations. Of the total particles in turbid water, clay constituted 63.9${\sim}$66.6% and silt 33.4${\sim}$36.1% to account for a combined total of 98.9 ${\sim}$ 100%. Sand made up less than 1.1%. The turbidity of river-type reservoir was also found to be mainly affected by the biomass of plankton in a non-rainfall period. During a rainfall period, however, the quantity and relative ratio of inorganic particles depending on the soil components affected turbidity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.199-204
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• 2000

In this study, the ZnS nanosized thin films that could be used for fabrication of blue light-emitting diodes, electro-optic modulators, and n-window layers of solar cells were grown by the solution growth technique (SGT), and their structural and optical properties were examined. Based on these results, the quantum size effects of ZnS were systematically investigated. Governing factors related to the growth condition were the concentration of precursor solution, growth temperature, concentration of aq. ammonia, and growth duration. X-ray diffraction patterns showed that the ZnS thin film obtained in this study had the cubic structure ($\beta$-ZnS). When the growth temperature was $75^{\circ}C$, the surface morphology and the grain size uniformity were the best. The energy band gaps of samples were determined from the optical transmittance valued, and were shown to vary from 3.69 eV to 3.91 eV. These values were substantially higher than 3.65 eV of bulk ZnS, demonstrating that the quantum size effect of SGT grown ZnS is remarkable. Photoluminescence (PL) peaks were observed at the positions corresponding to the lower energy than that to energy band gap, illustrating that the surface states were induced by the ultra-fineness of grains in ZnS films. Particularly, for the first time, it is reported for the SGT grown ZnS that the PL peaks were shifted depending on the grain size.

• Clean Technology
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• v.13 no.1 s.36
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• pp.34-45
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• 2007

Phase behavior of the ternary systems of water-insoluble simvastatin drug, which is well known to be effective drugs for hypercholesterolemia therapy, in solvent mixtures of dichloromethane and supercritical carbon dioxide was investigated to present a guideline of establishing operating conditions in the particle formation of the drugs by a supercritical anti-solvent recrystallization process utilizing dichloromethane as a solvent and carbon dioxide as an anti-solvent. The solubilities of simvastatin in the mixtures of dichloromethane and carbon dioxide were determined as functions of temperature, pressure and solvent composition by measuring the cloud points of the ternary mixtures at various conditions using a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The solubility of the drug increased as the dichloromethane composition in solution and the system pressure increases at a fixed temperature. A lower solubility of the drug was obtained at a higher temperature. The second half of this work is focused on the particle formation of the simvastatin drug by a supercritical anti-solvent recrystallization process in a cylindrical high-pressure vessel equipped with an impeller. Microparticles of the simvastatin drug were prepared as functions of pressure (8 MPa to 12 MPa), temperature (303.15 K, 313,15 K), feed flow rate of carbon dioxide, and stirring speed (up to 3000 rpm), in order to observe the effect of those process parameters on the size and shape of the drug microparticles recrystallized.

• 한국해양학회지
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• v.23 no.2
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• pp.76-88
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• 1988

Size distribution of suspended particulate materials (SPM) in the coastal waters of eastern Korea was studied using a laser particle size analyzer. Mean particle size (MPS) ranges from 3.69 to 8.40 ${\mu}m$ in surface waters, from 3.38 to 6.43 ${\mu}m$ in mid-depth waters, and from 3.88 to 8.30 ${\mu}m$ in near-bottom waters. For smaller MPS, the size distribution is unimodal, whereas it becomes polymodal as the MPS increases. Particle concentrations increased with the increases in MPS, suggesting that processes of adding larger particles in the waters such as resuspension of bottom sediments are more important in controlling MPS in the area than processes of removing smaller particles such as flocculation of fine particles. Observations of higher MPS near the coast in mid-depth waters, and at the continental slope in near-bottom waters appear to support the above idea. For surface waters with high MPS, mean particle density was noticably low, indicating the importance of biological activities in the formation of suspended particles.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.1
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• pp.57-69
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• 2001

The chemical, elemental and biochemical components of the suspended particulate matter (SPM) were investigated in order to quantify particulate organic matter (POM) and assess diet quality for suspension feeders in the southern coastal bay systems of Korea where the marine farming of the suspension feeders are most active, The intense field observation program was carried out seasonally in the three coastal bay systems of Chinhae, Gosung and Kangjin bays, The SPM was characterized as collective properties of organic carbon (POC), nitrogen (PON), phosphorus (PP) and more refined collective properties of protein (PPr), carbohydrate (PCHO) and chlorophyll a (Chl a) compound. Although the three coastal bays are regarded as phytoplankton based ecosystem, the SPM is not composed entirely with phytoplankton cells. Due to the shallow water depth, resuspension of bottom sediment contributes significantly to some of the regions. Therefore, concentration of SPM in the surface water did not co-vary with Chl a or PPr, PCHO. In general, temporal variation of POC, PON and Chl a contents in seawater were closely associated with phytoplankton biomass in the three coastal bays, However, PPr and PCHO contents in seawater were higher in Chinhae bay than in Gosung and Kangjin bays and Chl a PPr-N ratio was higher in Chinhae bay than in Kosung and Kangjin bays, since Chinhae bay is more eutrophicated than other bays. Average C : N ratios from regressions of POC and PON of SPM were 6.6, 6.6 and 5.0 in Chinhae, Gosung and Kangjin bays, respectively. SPM in Chinhae and Gosung bays appears to be made of largely phytoplankton cells and SPM in Kangjin bay appears to be contributed from the bacterial biomass due to the shallow water depth. N : P ratios from regressions of PON and PP of SPM were 10.8 and 14.7 in spring, and 18.2 and 24.6 in Chinhae and Gosung bays, respectively. With respect to the hypothetical Redfield molecule, phytoplankton appears to be limited by the lack of N and f in spring and summer, respectively, in the two bays, In Kangjin bay, N : P ratios from regressions of PON and PP of SPM were varied from 6.3 to 12.8 throughout the year. The low N : P ratio with resepct to the hypothetical Redfield molecule, phytoplankton growth appears to be limited by the lack of N-nutrients.

• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.59-67
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• 1995

This study was conducted to develope the automatic insulation system which control inside temperature of the greenhouse. For this purpose, the double- wall greenhouse and system which could automatically supply and discharge styrene pellets were constructed and abrasion of the pellets, blower ability, insulating property, transmittance and shading effect were analyzed by the experiments. The results obtained from this study can be summarized as follows : 1. It took an hour and fifteen minutes to supply and discharge about 2㎥ pellets in the experimental greenhouse. However, it is possible to reduce the operation time by proper selection of the blower and exhaust port, and by proper control of the supply and return pipe. 2. It was founded that the indirect delivery way was more profitable than the direct one in the supply and return of pellets. 3. When the transmittance was measured between 10 a.m. and 3 p.m., the average light transmissivity rate was 67%. 4. In winter nighttime, the inside temperature of the double- wall greenhouse with out the pellets was higher than the outside temperature by 3.4$^{\circ}C$ on an average. However, the inside temperature of the double - wall greenhouse with insulated area 73% was higher than the outside by one 6.6$^{\circ}C$ on an average, and the inside temperature of the greenhouse with insulated area 100% was higher than outside one by 13.5$^{\circ}C$ on an average. Therefore, it was proved that the insulating ability of the double - wall greenhouse in nighttime was excellent. 5. When the outside temperature was 36.9$^{\circ}C$ on an average, the inside temperature of the double- wail greenhouse with insulated area 100% was 3$0^{\circ}C$ on an average. As the inside temperature was lower than the outside one by 7$^{\circ}C$ on an average, we could know that the shading effects of the double- wall greenhouse were excellent in summer daytime.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.05a
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• pp.328-331
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• 2003

1) PM10의 질량농도는 평균 98.21 ${\mu}g$/$m^3$로 나타났으며, 최고농도는 330.56 ${\mu}g$/$m^3$로서 연간 기준치인 80 ${\mu}g$/$m^3$를 초과하였다. 또한 K(1.23 ${\mu}g$/$m^3$)>Ca(1.12 ${\mu}g$/$m^3$)>Na(0.79 ${\mu}g$/$m^3$)>Al(0.76 )>Fe(0.75 ${\mu}g$/$m^3$) 순으로서 높은 조성을 보였으며, Cd(2.72 ng/$m^3$)이 가장 낮은 질량 농도를 보였다. 2) Cd, Ni, Pb 및 Zn은 평균 지각농축계수가 10이상의 인위적인 기원으로 봄철과 여름철에 비하여 서풍계열의 바람이 우세한 겨울철에 매우 높은 값을 보였으며, 연구 지역의 서쪽에 인접한 사상공단과 서남쪽에 위치한 신평.장림공단으로부터 서풍계열의 바람을 타고 이동되었음을 알 수 있었다. 또한 이들 중금속은 조대입자보다는 미세입자의 조성에 많은 영향을 미치는 것으로 나타났으며, 평균 토양입자의 기여율은 9.5%로 나타났다. 3) PM10의 조성에 관여하는 금속 원소들은 토양, 해양 및 인위적인 오염물질에 의한 기원을 동시에 포함하고 있으나 해양기원보다는 토양 및 인위적인 기원들 간의 상관성이 우세하게 나타났다.