• KSBB Journal
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• v.17 no.6
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• pp.543-548
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• 2002

The enantioselective esterification of racemic ibuprofen catalyzed by a Candida rugosa lipase was studied according to reaction conditions such as a lipase concentration, reaction temperature, alcohol chain length and alcohol concentration. The S-(+)-ibuprofen alkyl esters prepared were converted to S-(+)-ibuprofen by hydrolysis with sulfuric acid as a catalyst. High conversions in the esterifications were obtained at 60$^{\circ}C$ and an equimolar ratio of octanol to ibuprofen. The initial reaction rate of the esterification decreased with increasing octanol concentration. Conversion and initial reaction rate increased with increasing alcohol chain length. Values of enantiomeric excess(ee) according to esterification reaction conditions did not change below 60$^{\circ}C$. On the other hand, values of conversion and ee for the chemical hydrolysis of S-(+)-ibuprofen alkyl esters were independent of alcohol alkyl chain length. Optical resolution of racemic ibuprofen was achieved by lipase catalyzed esterification and chemical hydrolysis. The separation method provided a high yield and enantioselectivity for the production of S-(+)-ibuprofen from racemic ibuprofen.

• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.731-736
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• 2010

In this study, the sulfonated SBS cation-exchange membrane was prepared by post-sulfonation. Degree of sulfonation(DS), water-uptake, ion exchange capacity and electrical resistance and conductivity of sulfonated SBS were investigated as a function of sulfonation time. The DS of sulfonated SBS membrane was increased with increasing the reaction time and concentration of sulfuric acid. The maximum value of DS was 24.0%. And also, the water uptake and ion exchange capacity of the sulfonated SBS membrane were increased as increasing the value of DS. The values of water uptake and IEC were 41.2% and 0.80 meq/g, respectively. The electrical resistance and conductivity of the membrane showed $23.6{\Omega}{\cdot}cm^2$ and $4.24{\times}10^{-4}S/cm$, respectively.

• Journal of the Korean Magnetics Society
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• v.22 no.1
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• pp.11-14
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• 2012

The composites of expanded graphite oxide and magnetic nanoparticle (Ni and Co) were synthesized by using simple chemical method. From the raw material natural graphite, the expanded graphite was fabricated using sulfuric acid and $1^{st}$ heat treatment at $600^{\circ}C$ for 1 hour. The expanded graphite was changed to expanded graphite oxide by 2nd heat treatment at $1050^{\circ}C$ for 15 sec and chemical oxidation. The expanded graphite oxide/1-methyl-2-pyrrolidone solution reacts with the magnetic nanoparticle to form a magnetic graphite oxide composite. These graphite-based materials were characterized by x-ray diffractometer, Raman spectroscopy, transmission electron microscope, and vibration sample magnetometer. We expect that these results of this paper were become basis research of graphite oxide composite.

• Journal of the Korean Chemical Society
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• v.27 no.5
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• pp.345-352
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• 1983

Using a column of macrorecticular gel beads impregnated with alcohol solution of diphenylcarbarzide (DPC), the enrichment of Cr(Ⅵ) ion in 0.1M sulfuric acid was investigated. The column performance was compared with respect to the types of solid support such as Amberlite XAD and Diaion HP. Diaion HP-20 was found to be most suitable for this purpose. The break through point was increased when increasing the amount of DPC absorbed in the resin and the concentrated sample solution showed higher break through capacity than the dilute one. The extraction of Cr(Ⅵ) was not affected by the presence of 100 ppm Fe(Ⅲ) which amounted to ten times of 10 ppm Cr(Ⅵ) and the presence of other metal ions which amounted to 100 times of 10 ppm Cr(Ⅵ). Because the used gel particles were effectively regenerated with methanol, they were able to be used repeatedly.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.323-330
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• 2002

The protonation equilibrium of 5-substituted 2-furaldehydes is investigated spectrophotometrically in aqueous sulfuric acid at $25^{\circ}C$ and the basicity constants(p$K_{BH+}$) of the substrates is calculated by means of the excess acidity method. The basicity constant of 5-metyl-2-furaldehyde having electron donating group is larger than that of 5- nitro-2-furaldehyde having electron withdrawing group. Difference between the basicity constants(p$K_{BH+}$) of these two compounds was about 3.25 pK unit. The m value which is the degree of solvation of the protonated substrate is similar to that of acetophenone having same protonation site. The dependence of p$K_{BH+}$ on m value shows good linear cor-relation.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.1
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• pp.123-130
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• 2007

The effects of hydrogen peroxide treatment on the reduction of waterworks sludge were investigated in this study. Sludge treated by peroxidation $H_2O_2$ oxidation) was dewatered using a pressure filter at 3atm. It was observed that $H_2O_2$ treatment at the acidic condition significantly reduce both cake water content and specific resistance to filtration (SRF), indicating the enhancement of dewaterability and filterability. The filterability by hydrogen peroxide treatment at pH 3.5 was better than acidic treatment and became comparable with polymer conditioning. The sludge filterability evaluated by SRF was optimal at a dose 2ml $H_2O_2$/sludge($0.02g\;H_2O_2/gTS$) after adjusting of pH to 3.5. The $H_2O_2$ oxidation at pH 3.5 also produced even more dewatered cake when compared with polymer conditioning. The reduction rate of sludge mass at an optimal condition showed 34% compared with untreated sludge. The effects of peroxidation on sludge properties including zeta potential, bound water and particle size were also evaluated. Peroxidation at the acidic condition reduced both bound water and zeta potential. By $H_2O_2$ combined with sulfuric acid leached iron caused Fenton's reaction, which showed a potential to significantly reduce the amount of solids mass and to produce more compact cake with higher filterability.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.152-152
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• 2016

Anodizing is a technology to generate thicker and high-quality films than natural oxide films by treating metals via electrochemical methods. It is a technique to develop metals for various uses, and extensive research on the commercial use has been performed for a long time. Aluminum anodic oxide (AAO) is generate oxide films, whose sizes and characteristics depending on the types of electrolytes, voltages, temperatures and time. Electrochemical manufacturing method of nano structure is an efficient technology in terms of cost reduction, high productivity and complicated shapes, which receives the spotlight in diverse areas. The sulfuric acid was used as an anodizing electrolyte, controlling its temperature to $10^{\circ}C$. The anode was 5083 Al alloy with dimension of $5(t){\times}20{\times}20mm$ while the cathode was the platinum. The distance between the anode and the cathode was maintained at 3 cm. Agitation was introduced by magnetic stirrer at 300 rpm to prevent localized temperature rise that hinders stable growth of oxide layer. In order to observe surface characteristics with applied current density, the electrolyte temperature, concentration was maintained at constant condition for $10^{\circ}C$, 10 vol.%, respectively. To prevent hindrance of stable growth of oxide layer due to local temperature increase during the experiment, stirring was maintained at constant rate. In addition, using galvanostatic method, it was maintained at current density of $10{\sim}30mA/cm^2$ for 40 minutes. The cavitation experiment was carried out with an ultrasonic vibratory apparatus using piezo-electric effect with modified ASTM-G32. The peak-to-peak amplitude was $30{\mu}m$ and the distance between the horn tip and specimen was 1 mm. The specimen after the experiment was cleaned in an ultrasonic, dried in a vacuum oven for more than 24 hours, and weighed with an electric balance. The surface damage morphology was observed with 3D analysis microscope. As a result of the investigation, differences were observed surface hardness and anti-cavitation characteristics depending on the development of oxide film with applied current density.

• Journal of the Korean Chemical Society
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• v.46 no.5
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• pp.444-456
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• 2002

To protect the occurrence of the oxidation of car body, we developed antioxidizing device made with sacrificial anode. Because car body is made of iron and iron-alloy and oxidation potential of Mg, Al and Zn is higher than that of iron, sacrificial anodes were made with Mg, Al and Zn. Accordingly, Mg, Al and Zn are better oxidizing than car body, iron and iron-alloy can be protected from oxidizing. We have made an antioxidizing device and evaluated their anti-corrosive effect for iron piece in the solution of hydrochloric, nitric and sulfuric acid using balance, SEM and XPS. When iron pieces were connected with antioxidizing device of car body, weight loss by oxidation was remarkably reduced and surface corrosion of iron piece was protected. It was shown that the surface of iron pieces which is not con-nected to the device was changed to iron(Ⅲ) oxide, Fe$_2$O$_3$. Therefore, if this device is attached to car body, corrosion and oxidation of car body will be reduced, considerably.

• Journal of the Korean Electrochemical Society
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• v.3 no.3
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• pp.152-156
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• 2000

The effect of cupric ion concentration on the throwing power has been studied in the electrodeposition of Cu on the porous reticular electrodes with the electrolytes of $CuSO_4\;and\;H_2SO_4$. Sulfuric acid electrolytes with lower concentration of $CuSO_4$ improved throwing power in electrodeposition of copper not only due to higher cathodic polarizability but also due to higher conductivity of the electrolytes. The increase in conductivity of the electrolytes at low concentration of $CuSO_4$ could be also illustrated by the decrease in viscosity of the electrolytes. It was found that both the throwing power and the limiting current density should be taken into account in the electrodeposition of Cu on the reticular electrodes. According to the experimental results, the electrolyte of 0.2M $CuSO_4$ and 0.5M $H_2SO_4$ was found to be the most appropriate condition at the current density of $10mA/cm^2$.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.96-102
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• 2010

Effects of specimen area on the corrosion rate of low alloy steel were studied in sulfuric acid solution. The corrosion behavior of specimen was tested by electrochemical impedance spectroscopy (EIS), linear polarization resistance measurement (LPR) and potentiodynamic polarization measurement. The surface was analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electron probe X-ray micro analyzer (EPMA). As surface area was increased, corrosion rate was increased by the effect of small anode-large cathode.