• Resources Recycling
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• v.12 no.5
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• pp.10-15
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• 2003

In this study, the separation of rare earths and aluminium from the dried powder of waste cerium polishing slurry was investigated. Since cerium oxide, 40％ of rare earths, is the most stable state in rare earth, the dissolution of cerium oxide in acid solution is not easy. Therefore the dissolution process of cerium oxide by sulfation was examined in order to increase the recovery of rare earth. The rare earths could be separated from aluminum by double salt precipitation using sodium sulfate.

• Journal of Microbiology and Biotechnology
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• v.12 no.2
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• pp.209-216
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• 2002

Bacillus sp. A56 was studied, because of its high flocculating activity. The flocculating substance produced by this strain was purified by ethanol precipitation, cetylpyridinium chloride (CPC) precipitation, and gel permeation chromatography (GPC). The FT-IR spectrum of the purified bioflocculant, designated as BF-56, showed typical characteristics of polysaccharides. The non-sugar substituents, and sugar components of BF-56 containing glucose, fucose, glucuronic acid, and galactose in an approximate molar ratio of 2.76:1.10:1:0.12, suggested that it was a novel bioflocculant with an estimated molecular mass of over $7{\times}10^3$ kDa. Rheological analysis of BF-56 revealed that it was a pseudoplastic that had higher apparent viscosity rate at dilute concentrations than those of zooglan. The solution of bioflocculant BF-56 exhibited non-Newtonian characteristics and it was compatible to high concentrations of salts such as KCl, NaCl, $CaCl_2,\;or\;FeCl_3.$ The present results suggested strong possibility of bioflocculant BF-56 to be fully applicable to industries such as wastewater treatment.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1084-1089
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• 2010

This study elucidates the formation mechanism of SnO plate observed during the precipitation reaction of a $SnCl_2$ aqueous solution. $Sn_{21}Cl_{16}(OH)_{14}O_6$ and $Sn_6O_4(OH)_4$ precipitates was formed at pH=3~5 and at pH=11, respectively. When the pH was in the range of 11.5~12.5, the $Sn_6O_4(OH)_4$ precipitates dissolved into $HSnO_2{^-}[Sn_6O_4(OH)_4+4OH^-={6HSnO_2{^-}+2H^+]$ and dissolved $HSnO_2{^-}$ ions reprecipitated to SnO plate $[HSnO_2{^-}+H^+=SnO+H_2O]$. The $Sn_6O_4(OH)_4$ precipitates completely transformed into SnO plate through a repeated process of dissolution-precipitation in the range of pH=11.5~12.5.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.2
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• pp.92-98
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• 2012

The co-precipitation technique has been applied to synthesize biphasic calcium phosphate (BCP). $Ca(NO_3)_2{\cdot}4H_2O$, $(NH_4)_2HPO_4$, TEOS and $Mg(NO_3)_2{\cdot}6H_2O$ as the starting materials was used. After the heat treatment of powder crystalline phases HAp and ${\beta}$-TCP analysis showed a mixed phase. The overall spectra appear to have mainly two modes corresponding to characteristic $PO^{3-}_4$ and $OH^-$ groups. After immersion in Hanks' Balanced Salt Solution (HBSS) for 1 week a precipitation started to be formed with individual small granules on the specimen surface. An MTT assay indicated that ionic substituted BCP powders had no cytotoxic effects on MG-63 cells, and that they have good biocompatibility.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.243-248
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• 2010

Si-substituted biphasic calcium phosphates (Si-BCP) were prepared by co-precipitation method. X-ray diffraction and fourier transform infrared spectroscopy were used to characterize the structure of Si-BCP powders. The Si-BCP powders with various Ca/(P+Si) molar ratio were carried out on structural change of hydroxyapatite (HAp) and ${\beta}$-tricalcium phosphate ($\ss$-TCP). The in-vitro bioactivity of the Si-BCP powders was determined by immersing the powders in SBF solution, after that observing the chemical composition and morphology change by X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.1
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• pp.34-41
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• 2002

CdS and $TiO_2$ nanoparticles were made by the precipitation method and sol-gel method, respectively, and they were mixed mechanically and then treated with the hydrothermal processing. CdS-$TiO_2$ composite particulate films were thus prepared by casting CdS-$TiO_2$ mixed sol onto $SnO_2$ conducting glass and a subsequent heat-treatment at $400^{\circ}C$. Again, the physico-chemical and photoelectrochemical properties of these films were controlled by the surface treatment with $TiCl_4$ aqueous solution. The photocurrents and the hydrogen production rates measured under the present experimental conditions varied in the range of $3.5{\sim}4.5mA/cm^2$ and $0.3{\sim}1.8cc/cm^2$-hr, respectively, and showed the maximum values at the $CdS/[CdS+TiO_2]$ mole ratio of 0.2. Also, the surface treatment with $TiCl_4$ aqueous solution caused a considerable improvement in the photocatalytic activity, Probably as a result of close contacts between the primary particles by the etching effect of $TiCl_4$ It was found that the photoelectrochemical performance of these particulate films could be effectively enhanced by this approach.

• Resources Recycling
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• v.12 no.6
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• pp.57-63
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• 2003

In this study, the separation of neodymium was investigated from NdFeB permanent magnet scrap. Decomposition and leach-ing process of NdFeB permanent magnet scrap by oxidation roasting and sulfuric arid leaching were examined. Neodymium could be separated from iron by double salt precipitation using sodium sulfate. The optimum conditions established for decom-position and leaching are as follows: oxidation roasting temperature is $500^{\circ}C$ for sintered scrap and $700^{\circ}C$ for bonded scrap, concentration of sulfuric acid in leaching solution is 2.0 M, leaching temperature and time is $50^{\circ}C$ and 2 hrs, and pulp density is 15%. The leaching yield of neodymium and iron was 99.4% and 95.7% respectively. The optimum condition for separation of neodymium by double-salt precipitation was 2 equivalents of sodium sulfate and $50^{\circ}C$ The yield of neodymium was above 99.9%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.6
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• pp.279-285
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• 2012

The co-precipitation technique has been applied to synthesize Biphasic Calcium Phosphate (BCP), Mg-BCP and Si-BCP. X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy were used to characterize the structure of synthesized BCP, Mg-BCP and Si-BCP powders. The results have shown that BCP and substitution of magnesium and silicon in the calcium deficient apatites revealed the formation of biphasic mixtures of Hydroxyapatite (HAp)/${\beta}$-Tricalcium phosphate (${\beta}$-TCP) ratios after heating at $1000^{\circ}C$. Ionic substituted BCP is able to develop a new apatite phase on the surface in contact with physiological fluids faster than BCP does. An MTT assay indicated that BCP, Mg-BCP, and Si-BCP powders had no cytotoxic effects on MG-63 cells, and that they have good biocompatibility.

• Korean Journal of Metals and Materials
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• v.49 no.12
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• pp.995-1000
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• 2011

The microstructure of Cu-24 wt.%Ag filamentary nanocomposite fabricated by a thermo-mechanical process has been investigated by transmission electron microscopy (TEM) observations. This study is focused on the stability of Ag filaments formed by cold drawing; the effects of thermal treatment on the precipitation behavior and distribution of Ag-rich precipitates were also investigated. The Ag filaments elongated along the <111> orientation were observed in Cu-rich ${\alpha}$ phase of the as-drawn specimen and the copper matrix and the silver filament have a cube on cube orientation relationship. Annealing at temperatures lower than $200^{\circ}C$ for the as-drawn specimen caused insignificant change of the fibrous morphology but squiggly interfaces or local breaking of the elongated Ag filaments were easily observed with annealing at $300^{\circ}C$. When samples were annealed at $400^{\circ}C$, discontinuous precipitation was observed in supersaturated Cu solid solution. Ag precipitates with a thickness of 7-20 nm were observed along the <112> direction and the orientation relationship between the copper matrix and the Ag precipitates maintained the same orientation relationship in the as-drawn specimen. The interface between the copper matrix and the Ag precipitates is parallel to {111} and micro-twins were observed in the Ag precipitates.

• KSBB Journal
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• v.10 no.1
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• pp.1-8
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• 1995

A lot of water soluble proteins and lipids are released from minced mackerel meat and lost into the washing waste during the leaching process of Kamaboko or surimi manufacture. The removed proteins and lipids are not only an edible things but also a big burden for treating the wastewater. In order to recover the proteins from the effluent and to use as food stuff, the "pH-shifting" treatment, a modified isoelectric point precipitation method, was tried. This method is based on a myogen-aggregation phenomenon, which occurs when a solution of sarcoplasmic proteins is acidified or alkalified beyond the critical pH zone of 2∼3 or 12∼13 respectively and then neutralized. The maximum amount of precipitation was obtained by shifting the pH of the wastewater from original pH to isoelectric point (pH 4) or alkali pH 12 and then changing to neutral pH. The precipitates were easily collected by filteration or centrifuging at 10,000rpm. The oils which were only floating in the washing wastewater are easily recovered by seperating with oil separator after pouring. The recovered proteins were slightly denaturated during this pH shifting precipitation process, while the composition of amino acids was good balance as a food.