• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.1989-1996
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• 2006

The $NiSO_4/CeO_2-ZrO_2 $catalysts containing different nickel sulfate and $CeO_2$ contents were prepared by the impregnation method, where support, $CeO_2-ZrO_2$was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of $CeO_2-ZrO_2$. The addition of nickel sulfate (or $CeO_2$) to $ZrO_2$ shifted the phase transition of $ZrO_2$ from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or $CeO_2$) and $ZrO_2$. A catalyst (10-$NiSO_4/1-CeO_2-ZrO_2$) containing 10 wt % $NiSO_4$ and 1 mole % $CeO_2$, and calcined at $600{^{\circ}C}$ exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of $CeO_2$was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.1
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• pp.15-21
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• 2011

Arsenic is one of the most abundant contaminant found in waste mine tailings, because of it's carcinogenic property, the countries like United states of America and Europe have made stringent regulations which govern the concentration of arsenic in drinking water. The current study focuses on different treatment methods for removal of arsenic from waste water. Treatment method the high strength arsenic waste water is treated with Fe(III)-ettringite by co-precipitation method. Number of experiments were carried out to decide the optimal dosage of Fe(III)-ettringite to treat arsenic waste water. The Fe(III)-ettringite was synthesized by taking appropriate equivalent ratios of calcium oxide and ferric chloride in proportion to the arsenic. The best removal efficiencies of 94% were observed at a As/(Ca: Fe) ratio of 1:3. The maximum removal of arsenic was observed in pH range of 12. But as the pH increases the arsenic removal efficiency decreases as portlandite is formed in the pH above 12. The analysis of surface of precipitate conform the needle like structure of ettringite. This treatment technique has promising features such as, the chemicals required in the treatment as well as the sludge generated can be reduced. The operating pH range is in alkaline region which is advantageous over traditional treatment process which has lower pH. Also the co-precipitation not only helps in removal of arsenic but also heavy metals.

• Microbiology and Biotechnology Letters
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• v.48 no.1
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• pp.12-23
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• 2020

Edible films containing antimicrobial agents can be used as safe alternatives to preserve food products. Essential oils are well-recognized antimicrobials. However, their low water solubility, volatility and high sensitivity to oxygen and light limit their application in food preservation. These limitations could be overcome by embedding these essential oils in complexed product matrices exploiting the encapsulation efficiency of β-cyclodextrin. This study focused on the maximization of β-cyclodextrin production using cyclodextrin glucanotransferase (CGTase) and the evaluation of its encapsulation efficacy to fabricate edible antimicrobial films. Response surface methodology (RSM) was used to optimize CGTase production by Brevibacillus brevis AMI-2 isolated from mangrove sediments. This enzyme was partially purified using a starch adsorption method and entrapped in calcium alginate. Cyclodextrin produced by the immobilized enzyme was then confirmed using high performance thin layer chromatography, and its encapsulation efficiency was investigated. The clove oil/β-cyclodextrin inclusion complexes were prepared using the coprecipitation method, and incorporated into chitosan films, and subjected to antimicrobial testing. Results revealed that β-cyclodextrin was produced as a major product of the enzymatic reaction. In addition, the incorporation of clove oil/β-cyclodextrin inclusion complexes significantly increased the antimicrobial activity of chitosan films against Staphylococcus aureus, Staphylococcus epidermidis, Salmonella Typhimurium, Escherichia coli, and Candida albicans. In conclusion, B. brevis AMI-2 is a promising source for CGTase to synthesize β-cyclodextrin with considerable encapsulation efficiency. Further, the obtained results suggest that chitosan films containing clove oils encapsulated in β-cyclodextrin could serve as edible antimicrobial food-packaging materials to combat microbial contamination.

• Journal of the Korean Electrochemical Society
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• v.14 no.2
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• pp.98-103
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• 2011

[ $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ ]cathode material for lithium secondary battery is obtained using co-precipitation method. To determine the optimal metal solution concentration value, the CSTR coprecipitation was carried out at various concentration values(1-2 mol/L). The surface morphology of coated samples was characterization by SEM(scanning electron microscope) and XRD (X-Ray Diffraction)analyses. Impedance analysis and cyclic voltammogram presented that internal resistance of the cell was dependent upon the concentration of metal solution. such data is very helpful in determining the optimal content of metal solution concentration to enhancing electrochemical property by adjusting powder size distribution and crystal structure.

• Journal of Pharmaceutical Investigation
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• v.25 no.3
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• pp.205-211
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• 1995

To increase the solubility of iodine and iodine releasing agents, which are used widely as a topical broad spectrum antiseptics and disinfectant sanitizers, its inclusion complexes were prepared and studied. Inclusion complexes of iodine with ${\beta}-cyclodextrin$ were prepared by coprecipitation method and complex formation was acertained by differential scanning calorimetry and microscopic observation. Iodine content of inclusion complex was determined by means of iodometry. Tablets containing inclusion complex were manufactured with sugar, citric acid, magnesium stearate, dextrose. Stability of inclusion complexes and tablets was evaluated by accelerated stability test, and comparing with PVP-iodine. During preparation, use of 50% ethanol solution is preferable to water as the medium because the former resulted in more stable complex for a month under accelerated storage conditions. Solubility of iodine in KI aqueous solution was 0.048 g/ml and lower than in 50% ethanol solution. Inclusion complex and its tablets were very stable at severe condition for one month, and comparable to PVP-iodine in the aspect of stability. Inclusion complex tabletswere not affected with citric acid, sugar, dextrose, and direct tableting method was recommendable because wet granulation using ethanol gave some release of included iodine during process.

• Journal of Powder Materials
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• v.26 no.1
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• pp.49-57
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• 2019

Layered $LiNi_{0.83}Co_{0.11}Mn_{0.06}O_2$ cathode materials single- and dual-doped by the rare-earth elements Ce and Nd are successfully fabricated by using a coprecipitation-assisted solid-phase method. For comparison purposes, non-doping pristine $LiNi_{0.83}Co_{0.11}Mn_{0.06}O_2$ cathode material is also prepared using the same method. The crystal structure, morphology, and electrochemical performances are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping, and electrochemical techniques. The XRD data demonstrates that all prepared samples maintain a typical ${\alpha}-NaFeO_2$-layered structure with the R-3m space group, and that the doped samples with Ce and/or Nd have lower cation mixing than that of pristine samples without doping. The results of SEM and EDS show that doped elements are uniformly distributed in all samples. The electrochemical performances of all doped samples are better than those of pristine samples without doping. In addition, the Ce/Nd dual-doped cathode material shows the best cycling performance and the least capacity loss. At a 10 C-rate, the electrodes of Ce/Nd dual-doped cathode material exhibit good capacity retention of 72.7, 58.5, and 45.2% after 100, 200, and 300 cycles, respectively, compared to those of pristine samples without doping (24.4, 11.1, and 8.0%).

• Analytical Science and Technology
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• v.10 no.3
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• pp.203-208
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• 1997

Barium titanyl oxalate(BTO) was precipatated by utilizing the thermal decomposition of dimethyl oxalate in acidic aqueous solution having $BaCl_2$ and $TiCl_4$. Particle morphology of BTO was influeneced by the various experimental factors. i.e.. the faster rate to nucleation with higher temperature and the higher ratio of [DMO]/[$Ba^{2+}+Ti^{4+}$] was found to correspond to the faster rate of transformation of particle size distribution from unimodal to broad unimodal through bimodal. The BT powder obtained by calcination at $900^{\circ}C$ in air consists of larger particles than BT generated by general coprecipitation method and shows tetragonal symmetry. The stirring during reaction was also found to have much effect upon characteristics of BTO and BT.

• Analytical Science and Technology
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• v.9 no.1
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• pp.26-34
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• 1996

A method to determine the trace amount of Se and Bi in the scalp hair using the hydride generation inductively coupled plasma atomic emmission spectrometry was studied. The optimum operation conditions of ICP for hydride generation are 0.6~0.8L/min for the carrier gas flow rate, and 6mm above the induction coil for the observation height. Hydrochloric acid concentrations for the optimum hydride generation conditions were greater than 1.5M when 2.5% $NaBH_4$ and NaOH were used, and greater than 0.5M when 2.5% $NaBH_4$ and 0.1% NaOH were used. Severe interference effects are observed from transition metals such as Cu and Ni, and they could be circumvented by the coprecipitation with lanthanum hydroxide.

• Polymer(Korea)
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• v.36 no.3
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• pp.287-294
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• 2012

ZnAl-LDH(layered double hydroxide) (Zn:Al=2:1 mole ratio) modified with stearic acid (SA) or oleic acid (OA) was synthesized by a coprecipitation method and compounded to SAN polymer at various contents. All the SAN composites were manufactured by a co-rotating twin-screw extruder and subsequently injection molded into several specimen. Morphology, transparency, and thermal resistance of these composites were evaluated by TEM, XRD(X-ray diffractometry), UV-Vis spectrophotometry, and thermogravimetric analysis. SAN nanocomposites containing OA-$Zn_2Al$ LDH showed better optical transmittance than SAN nanocomposites containing SA-$Zn_2Al$ LDH. All the SAN nanocomposites containing OA-$Zn_2Al$ LDH or SA-$Zn_2Al$ LDH exhibited improvement of thermal resistance at second stage of thermal oxidation. These results were explained by the fact that the interaction between organic modifier and polymer performed an important role in the property improvement of polymer nanocomposites.

• Journal of the Korean Chemical Society
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• v.39 no.10
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• pp.806-811
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• 1995

The electrical properties for $(Ba,Sr)_{1-x}Y_xTiO_3$(x=0.001∼0.009, BSYT) with a positive temperature coefficient of resistivity(PTCR) effect were investigated. The BSYT powder was prepared by oxalate coprecipitation method. It was found that the large PTCR effect was appeared up to 0.3 mol% and decreased above 0.5 mol% of the yttrium concentration. The plot of temperature vs. $1{\varepsilon}$m(T) above Curie temperature($T_c$) was agreed with Curie-Weiss law. The potential barrier calculated from measured resistivity and dielectric constant of specimens was high up to 0.3 mol% and reduced above 0.5 mol% of yttrium concentration as the curve of PTCR effect.