• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.284-288
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• 2004

To improve mechanical properties of $Al_2$O$_3$/ZrO$_2$composites have been controlled dispersion of ultra low size ZrO$_2$ particles in $Al_2$O$_3$ ceramics by polymeric precursor method (Pechini process). In case of coprecipitation or mechanical mixing of ZrO$_2$ powders with $Al_2$O$_3$, homogeneous dispersion and controlling the ZrO$_2$ size were relatively difficult due to high sintering temperature. So the polyesterization process of Zr/Y(NO$_3$)$_3$-citric acid solution in ethylene glycol with the commercial sub-micron sized o(-alumina powder (Sumitomo AES-11(0.4 ${\mu}{\textrm}{m}$)) was adopted in order to obtain homogeneous dispersion of ZrO$_2$ in A1203. By this partial polyesterization process, the homogeneous dispersion of relatively low sized ZrO$_2$in $Al_2$O$_3$/ZrO$_2$composites was achieved at 1450∼1$600^{\circ}C$ of sintering temperature range and their mechanical properties were measured.

• 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 the Korean Ceramic Society
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• v.38 no.11
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• pp.1030-1036
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• 2001

Hydroxyapatite[COL] nanocomposite was prepared through coprecipitation process. The chemical bond formation between HAP and COL was confirmed by diffusive reflectance FT-IR and TEM observation. Higher concentration of COL in the preparation induced tiny nanocrystalline composite particles, but lower concentration of COL contributed to form the well developed HAP particles. From TEM observation and ED(Electron Diffraction) pattern the embedded HAP nanoparticles were oriented along the c-axis of COL fiber. In an aqueous system of constant [Ca$\^$2+/] and [PO$_4$$\^$3-/], quantity of soluble COL matrix was doing an important role of controlling the heterogeneous nucleation site for the formation of HAP nanocrystals. Higher concentration of COL will provide more nucleation sites for Ca$\^$2+/ and so the concentration of calcium ions for the total number of active nucleation sites will be getting relatively dilute.

• Journal of the Korean Ceramic Society
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• v.33 no.9
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• pp.1057-1063
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• 1996

Y2O3-CeO2-ZrO2 powders were prepared from water-soluble salts using a coprecipitation method. The forming process of oxide and the characteristics of the calcined powders treated in different drying conditions were investigated. The oxidation was occurred at the temperature of around 40$0^{\circ}C$ and the main crystallization of ZrO2 around $600^{\circ}C$. On calcination at $600^{\circ}C$ heating lamp-dried powders consisted of agglomerates of globular morphology with average agglomerate size of 2.27${\mu}{\textrm}{m}$ and specific surface area of 68.3m2/g and spray dried powders contained dense spheric particles with average agglomerate size of 1.35${\mu}{\textrm}{m}$ and specific surface area of 11.0m2/g which exhibited low agglomeration tendency. Removal of the water by a freeze-drying technique produced calcined powders containing flake-like secondary particle structures with wide agglomerate size distri-bution of 0.1-60${\mu}{\textrm}{m}$ and specific surface area of 24.5${\mu}{\textrm}{m}$. The 20 MPa-pressed density (36.8-41.4% T,D) of calcined powders did not nealy depend on drying methods whilst compaction ratio of calcined powders derived from freeze-drying was the highest ( 6.24) among three drying methods. On continuous heating up to 150$0^{\circ}C$ the sinterability of calcined powders derived from heating lamp-drying was superior to those derived from spray-and freeze-drying. The final sintered density of calcined powders was the highest (96% T,D at 150$0^{\circ}C$) in case of heating lamp-drying.

• 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.

• Resources Recycling
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• v.20 no.3
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• pp.28-39
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• 2011

This review investigated theoretical principals and practical application examples on recirculation system of soil washing-wastewater treatment-treated water recycling. As for technologies which have attempted to remediating metals-contaminated soil in and around country, there are reactive barriers, encapsulation, solidification/stabilization, soil washing, and phytoremediation. Among those, in particular, this review covers soil washing technology which physicochemically removes contaminants from soils. The major drawbacks of this technology are to generate a large amount of wastewater which contains contaminants complexed with ligands of washing solution and needs additional treatment process. To solve these problems, many chemical treatment methods have been developed as follows: precipitation/coprecipitation, membrane filtration, adsorption treatment, ion exchange, and electrokinetic treatment. In the last part of the review, recent research and field application cases on soil washing wastewater treatment and recycling were introduced. Based on these integrated technologies, it could be achieved to solve the problem of soil washing wastewater and to enhance cost effective process by reducing total water resources use in soil washing process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.2
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• pp.93-100
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• 2010

The calcium to phosphate ratio (Ca/P) in biphasic calcium phosphates powders using X-ray diffraction analysis (XRD) was characterized. The BCP powders with various stoichiometric Ca/P molar ratio were synthesized with coprecipitation process and calcination. Compositions of the powders with Ca/P molar ratio between 1.5 and 1.67 were subjected to starting Ca/P molar ratio, pH = 10, and thermal treatment up to $900^{\circ}C$. The structural, morphological and chemical characterizations for BCP powders with stoichiometric Ca/P ratio were carried out with scanning electron microscope (SEM) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) and a phase quantification was investigated by XRD. The solubility of HAp, $\beta$-TCP, and BCP powders was tested in the phosphate buffer solution (PBS) at $36.5^{\circ}C$ and pH = 7.4.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.4
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• pp.204-209
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• 2015

The effluent limit of nickel from electroplating wastewater has been strengthened from 5 mg/L to 3 mg/L from 2014. However, currently applied treatment process for nickel plating wastewater is unable to meet the effluent limit, most of the treatment concept conducted by treatment plant is dilution with other metal bearing wastewater. This can cause very significant impact to the environment of nickel contamination. With this connection, the feasibility test has been conducted with the use of electrolysis by using sacrificial electrodes. Experiments were conducted in synthetic and electroless nickel plating wastewater. Optimal condition of current density, pH were derived from the synthetic wastewater. It was found that the removal efficiency of nickel exceeded 94% at the operation condition of at pH 9 and the current density of $1{\sim}2mA/cm^2$. At this conditions, the iron sludge was generated very low amount. However, it was unsuccessful to meet the effluent limit by applying these treatment conditions to the real electroplating wastewater. This can be explained due to the matrix effect of other metals and anions contained real electroplating wastewater. From the result of further study, the optimal conditions for the real wastewater treatment were found out to be at pH 9, current density $6{\sim}7mA/cm^2$, for 5 minutes of operating time. At these conditions, 88% removal of nickel was achieved, which results the residual nickel concentration was below 3 mg/L.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.886-893
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• 2001

We synthesized $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ powders by coprecipitation, citration and solid-state reactions. The oxygen permeation membranes were fabricated by cold isostatic pressing of the synthesized powders, followed by sintering in air. All powders and membranes consist of perovskite phases. The coprecipitated powders showed the highest surface area ($7.5m^2/g$) but strontium deficiency was found during washing and filtering in the process. The membrane with lower relative density was fabricated by citration method. On the other hand, solid state reacted powders had high relative density (95%), and mechanical properties showed superior properties. Especially, the composition of the solid-state reacted powders was relatively well-controlled.