• 한국환경보건학회지
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• 제34권2호
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• pp.175-182
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• 2008

This study investigates the optimal conditions for electrogenerated hydrogen peroxide production and the application of the electro-Fenton process using DSA electrodes. The influences of parameters for the hydrogen peroxide generation such as electrode materials, electrolyte concentration, current, pH, air flow rate and electrode distance were investigated using a laboratory scale batch reactor. The relative performance for hydrogen peroxide generation of each of the six electrodes is : Ru-Sn-Ti > Ru-Sn-Sb > Ru > Ir > Pt > Sn-Sb. Optimum NaCl dosage, current and air flow rate were 2.0 g/l, 12.5 A and 2 l/min, respectively. When the pH is low, hydrogen peroxide concentration was high. Electrode distance dos not effect to a hydrogen peroxide generation. A complete color removal was obtained for RhB (200 mg/l) at the 8 min mark of the electro-Fenton process under optimum operation conditions of $Fe^{2+}$ 0.105 g/l and 5.0 A. The electro-Fenton process increased initial reaction and decreased final reaction time. However the effect was not high.

• 한국환경과학회지
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• 제11권9호
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• pp.955-960
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• 2002

The recycled washwater, which has different water quality and is produced about 5 to 20% of the total water volume treated, affects the unit operation of water treatment, especially coagulation process. However, the effects of recycled washwater on unit operation of water treatment have not been fully investigated. In this study, effects of recycled washwater on coagulation process were investigated to find the optimum coagulation condition by analyzing turbidity, $UV_{254}$, TOC removal efficiencies. In addition, effects of recycled washwater on residual Al after coagulation were studied by analyzing soluble and particulate Al. The size distribution and fractal dimension of coagulated also analyzed. The recycled washwater was lower pH than the raw water. And the recycled washwater had higher $UV_{254}$, TOC and residual Al concentration than the raw water. Residual Al concentration of recycled washwater was about 50 times higher than that of raw water. Optimum coagulant dosages on the blending recycled washwater and the raw water for turbidity, $UV_{254}$ and Al removal were lower than that on the raw water. However, TOC removal increased by increasing coagulant dosage. The size and fractal dimension of coagulated particle produced in the blending recycled washwater were larger, which imply faster settling velocity, than those produced in the raw water only.

• 한국환경과학회지
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• 제19권1호
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• pp.89-96
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• 2010

The separation of $TiO_2$ wastewater carried out by an electrocoagulation/flotation process, which had various operating parameters. The effect of electrode material (aluminum and four dimensionally stable electrode), applied current (0.07~0.5 A), electrolyte concentration (0~1 g/L), solution pH (3~11), initial turbidity (1000~20000 NTU) and suspended solid concentration (5000~25000 mg/L) were evaluated. Turbidity removal efficiency of the soluble anode (aluminum), which could produce metal ions, was higher than that of the dimensionally stable electrode. Considering operation time, turbidity removal and electric power, optimum current was 0.19 A. The more NaCl dosage was high, the less electric power was required. However, optimum NaCl concentration was 0.125 g/L considered removal efficiency, operation time and cost. Initial $TiO_2$ concentration did not affected turbidity removal on the electrocoagulation/flotation operation. The electrocoagulation/flotation process was proved to be a very effective separation method in the removal of $TiO_2$ from wastewater.

• KSBB Journal
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• 제9권2호
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• pp.127-132
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• 1994

Amyloglucosidase를 이용하여 설탕으로부터 fructooligosaccharides의 생산조건을 최적화하였다. Amyloglucosidase의 두 가지 활성 중 가수분해 활성에 대한 최적반응 pH 및 온도는 각각 4.0, $75^{\circ}C$ 이었고, 올리고당 합성에 대한 활성은 pH 5.5, 온도 $55^{\circ}C$에서 최고치를 나타내었다. 저농도 설탕에서는 가수분해 활성이 대단히 강하여 fructooligosaccharides의 합성능이 매우 낮았고, 550g/l 이상의 설탕을 기질로 이용하였을 때 최적반응조건에서 최대 41%의 fructooligosaccharides를 생산할 수 있었다. 또한 Amyloglucosidase는 설탕뿐만 아니라 fructooligosaccharides도 기질로 이용할 수 있었다.

• 상하수도학회지
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• 제19권4호
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• pp.473-479
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• 2005

Applying enhanced coagulation is not uncommon not only to improve water quality but also to obtain economical advantages in water treatment. In this study, the economical evaluation was investigated with considering dosage of coagulant, produced sludges and usage of activated carbon with two different water sources. To simulate the granular activated carbon(GAC) adsorber mini-column test was adapted. Even if there were some variation according to the source waters, the life time of GAC was extended 60 to 110days with adding 2.5 to 3 times of coagulant in enhanced coagulation. With assumption of changing GAC adsorber at 50% of breakthrough the total treatment cost can be reduced to range from 25% to 44% with adapting the enhanced coagulation. The obtained value can not be generalized because the value can be varied by water quality and cost of the GAC or coagulant. However, the evaluation can be basis starting point to find optimum operation methods for the drinking water treatment which has plan to adapt GAC adsorber.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.549-554
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• 2002

In Powder System, SCC demands high dosage of superplasticizer and a lage amout of powder for suitable fluidity and viscosity. Okamura's method of most representative mixing design method in SCC of Powder-System is unfavorable economically because of using a large amount of powder. In addition, many ready-mixed concrete plants do not use his mix design method and procedure due to complexity for practical application. Therefore, Nan Su proposed more simple mix design method than Okamura's. It had an advantage in simplicity in practical application and required a smaller amount of powders compared with Okamura's method. This paper proposed an optimal mixture proportion of SCC with consideration of Nan Su's method. The new and modified mix design method required a smaller amount of powder than that of Nan Su's. To check the properties of SCC, considered with the requirements specified by the Japanese Society of Civil Engineering.(JSCE)

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.175-178
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• 1999

In most domestic construction fields, excessive cement content has been used because of stubborn official inspection. The purpose of this study is to reduce the cement content of mix proportioning for the decrease of hydration heat, brittleness and drying shrinkage which governs durability of concrete significantly. Parameters includes the compressive strengths, type and dosage rate of chemical and mineral admixtures and types of concrete. It is found that the chemical admixture is efficient to the reduction of cement content for high strength concrete (400kg/$\textrm{cm}^2$) and the effectiveness of mineral admixtures in the low strength concrete is somewhat higher than the high strength concrete.

• 한국세라믹학회지
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• 제44권2호
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• pp.103-109
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• 2007

In this study, the rheological properties of cement pastes containing blastfurnace slag of different fineness were investigated. The fluidity of cement pastes with low Blaine value blastfurnace slag was increased with decreasing the plastic viscosity and the yield stress of pastes. And the optimum dosage of polycarboxylate type superplasticizer to the cement pastes was confirmed according to the fineness and the replacement ratio of blastfurnace slag. All cement pastes showed the thixotropy behavior. And also it was formed that the segregation range of cement pastes was occurred below $10D/cm^2$ of the yield stress and below 350 cPs of the plastic viscosity by the coaxial cylinder viscometer.

• 한국환경과학회지
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• 제12권12호
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• pp.1277-1284
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• 2003

The photocatalytic oxidation of Rhodamine B (RhB) was studied using immobilized TiO$_2$ and fluidized bed reactor. Immobilized TiO$_2$ onto GF/C was employed as the photocatalyst and a 30 W germicidal lamp was used as the light source and the reactor volume was 4.8 L. The effects of parameters such as the amounts of photocatalyst, initial concentration, initial pH, air flow rate and anion additives (NO$_3$$\^$-/, SO$_4$$\^$2-/, Cl$\^$-/, CO$_3$$\^$2-/) competing for reaction. The results showed that the optimum dosage of the immobilized TiO$_2$ was 40.0 g/L. Initial removal rate of immobilized TiO$_2$ was expressed Langmuir - Hinshelwood equation.

• 펄프종이기술
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• 제33권2호
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• pp.68-73
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• 2001

This experiment was executed to clarify the optimum condition of reductive bleaching for 100% color papers. The reductive bleaching of the color paper was desirable to be done under such conditions as high temperature over $60^{\circ}C$ and high consistency within possibly short time. The FAS bleaching like the sodium hydrosulfite required oxygen-free condition. Especially, as the mixture between pulps and chemicals was favored in case of the high consistency, it was actively recommended. Therefore, it is desirable to control the dosage with the type of the dyes, the nature, the dye content, the paper compositions, and the targeting initial and final brightness.