• Microbiology and Biotechnology Letters
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• v.42 no.3
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• pp.232-237
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• 2014

We investigated the effects of silica gels on the reduction of the crystallization time for the purification of vancomycin. The shortest crystallization time for vancomycin was obtained when silica gel with a pore diameter of $40-60{\AA}$ and with a particle diameter of 230-400 mesh was used as the material. The use of silica gel as a surface area increasing material dramatically reduced the crystallization time four fold (6 h) when compared with the results where the surface area had not been similarly increased. In addition, the crystal size of vancomycin was decreased with the addition of silica gel. This improved crystallization process has a significant effect on the convenience and feasibility of the purification step for vancomycin.

• Journal of Environmental Health Sciences
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• v.23 no.4
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• pp.133-138
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• 1997

The technology of removing phosphorous, considered as one of the most important control nutrients causing eutrophication in various water bodies, have been investigated by many researchers. Recently, phosphorous crystallization process is emerging as a new technology for phosphorous removal. In this study, waste oyster shells which can be easily obtained from the ocean, were used as a seed crystal, and their effects of several physical/chemical factors on the phosphorous removal efficiencies were examined by batch tests. Ca$^{2+}$ and pH affected phosphorous crystallization process using waste oyster shells. As alkalinity of wastewater increased, phosphorous removal efficiencies gradually decreased. Phosphorous removal efficiencies were increased, as specific area and contact efficiency per unit area of waste oyster shells were increased. In case of high temperature, phosphorous crystallization process was rapidly advanced and phosphorous removal efficiencies were increased. Dependig on X-ray diffraction analysis, it was showed that generation materials extracted from the surface of waste oyster shells with short reaction time were dominated by $CaHPO_4\cdot 2H_2O$, but progressed to $Ca_5(OH)(PO_4)_3$. The SEM observation reveals that the evident variations were hardly seen, but particle sizes of waste oyster shells were relatively bigger and showed forms of smaller plate than before.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.4
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• pp.210-214
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• 2002

The crystallization behavior of amorphous silicon (a-Si) film was investigated by using Cu-field aided lateral crystallization (Cu-FALC) process below $450^{\circ}C$. The lateral crystallization was induced from the Cu deposited region outside of pattern toward the Cu-free region inside of the pattern by applying an electric field during heat treatment. As expected, the lateral crystallization toward Cu-free region proceeded from negative toward positive electrode side. The occurrence of Cu-FALC phenomenon was interpreted in terms of dominant diffusing species in the reaction between Cu and Si. Even at the annealing temperature of $350^{\circ}C$, the large dendrite-shaped branches were formed in the crystallized region and the polarity in the lateral crystallization was clearly observed. Consequently, we could successfully crystallize the a-Si at the temperature as low as $350^{\circ}C$ by an electric field of 30 V/cm with fast crystallization velocity of 12 $\mu$m/h.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.2
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• pp.207-215
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• 2014

Wastewater containing heavy metals such as copper (Cu) and nickel (Ni) is harmful to humans and the environment due to its high toxicity. Crystallization in a fluidized bed reactor (FBR) has recently received significant attention for heavy metal removal and recovery. It is necessary to find optimum reaction conditions to enhance crystallization efficacy. In this study, the effects of crystallization reagent and pH were investigated to maximize crystallization efficacy of Cu-S and Ni-S in a FBR. CaS and $Na_2S{\cdot}9H_2O$ were used as crystallization reagent, and pH were varied in the range of 1 to 7. Additionally, each optimum crystallization condition for Cu and Ni were sequentially employed in two FBRs for their selective removal from the mixture of Cu and Ni. As major results, the crystallization of Cu was most effective in the range of pH 1-2 for both CaS and $Na_2S{\cdot}9H_2O$ reagents. At pH 1, Cu was completely removed within five minutes. Ni showed a superior reactivity with S in $Na_2S{\cdot}9H_2O$ compared to that in CaS at pH 7. When applying each optimum crystallization condition sequentially, only Cu was firstly crystallized at pH 1 with CaS, and then, in the second FBR, the residual Ni was completely removed at pH 7 with $Na_2S{\cdot}9H_2O$. Each crystal recovered from two different FBRs was mainly composed of CuxSy and NiS, respectively. Our results revealed that Cu and Ni can be selectively recovered as reusable resources from the mixture by controlling pH and choosing crystallization reagent accordingly.

• Proceedings of the Korean Fiber Society Conference
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• 1986.06a
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• pp.14-14
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• 1986

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.415-415
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• 2006

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.664-672
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• 2010

This study was performed to evaluate the feasibility of industrial by-products such as converter slag, olivine, red mud and fly ash as a seed crystal of struvite crystallization for the removal of highly concentrated $NH_4-N$ and $PO_4-P$. In the kinetic experiments, more than 90% of $NH_4-N$ and $PO_4-P$ was eliminated by struvite crystallization within 30 minutes of reaction time. The pH range in meta-stable region of struvite crystallization was found to be pH 7.0~9.0 under the Mg:N:P=1:1:1 equi-molar condition with 100 mg/L of $NH_4-N$. Total removal efficiencies of $NH_4-N$ and $PO_4-P$ by both struvite precipitation and crystallization were increased with the increase of pH. Removal efficiencies of $NH_4-N$ and $PO_4-P$ were significantly enhanced by struvite crystallization using industrial by-products as a seed crystal compared with those by struvite precipitation without seed crystal. Red mud, converter slag, olivine and fly ash enhanced the removal efficiencies of $NH_4-N$ by 40.9%, 37.7%, 28.4% and 16.4%, respectively. Removal efficiencies of $PO_4-P$ for converter slag, red mud, fly ash, olivine were increased by 3.7 times, 2.6 times, 72.4% and 68.0%, respectively. Converter slag and red mud showed higher feasibility as a seed crystal than others for the removal of highly concentrated $NH_4-N$ and $PO_4-P$. In particular, converter slag might have a high capacity of phosphorus removal.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.5
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• pp.229-233
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• 2002

Nano-sized ZnO particles were successfully synthesized at low temperatures by a polymerized complex method via an organochemical route. The polymeric precursors could be prepared using Zn nitrate hexahydrate and a mixed solution of citric acid and ethylene glycol as a chelating agent and a reaction medium. The polymeric precursors were calcined at temperatures from 300 to $700^{\circ}C$ for 3 h, and evaluated for degree of crystallization process, thermal decomposition, surface morphology and crystallite size. The thermal decomposition and crystallization process were analyzed by TG-DTA, FI-IR and XRD. The morphology and crystallite size of the calcined particles were evaluated by scanning electron microscopy (SEM), transmittance electron microscopy (TEM) and Scherrer's equation. Crystallization of the ZnO particles was detected at $300^{\circ}C$ and entirely completed above $400^{\circ}C$. Particles calcined between 400 and $700^{\circ}C$ showed a uniform size distribution with a round shape. The average particle sizes calcined at $400^{\circ}C$ for 3 hour were 30~40nm showing an ordinary tendency to increase with the temperatures.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.916-921
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• 2009

This study was aimed to both enhance the fluoride removal and to reduce the phosphorus removal in treating semiconductor wastewater using $Ca(OH)_2$ at low pH so as to facilitate struvite crystallization reaction. The struvite crystallization could be introduced after fluoride removal by retaining the phosphorus source. As the results, the method applied in this study achieved high fluoride removal efficiency (about 91%) with retardation of phosphorus removal at pH 4, compared to conventional methods where the removal of fluoride and phosphorus were done at pH 11. Therefore, the fluoride removal at low pH would contribute to the enhancement of nitrogen and phosphorus removals in a consecutive struvite crystallization reactor. Treatment of semiconductor wastewater at low pH using $Ca(OH)_2$ also had lower (about 20%) water content of precipitated sludge compared to conventional method. As the molar ratio of Ca to F increased the removal efficiencies of fluoride and phosphorus increased. Although the amount of seed dosage didn't affect the removal of fluoride and phosphorus, its increase reduced the water content of precipitated matter. Finally, considering consecutive struvite reaction, the optimum condition for the removal of fluoride and phosphorus was as follow: pH: 4, the molar ratio of Ca:F: 1:1.

• Journal of the Korean Ceramic Society
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• v.19 no.3
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• pp.236-240
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• 1982

The crystallization of melts with similar composition of Portland cement liquid containing 0-5% $K_2O$ was studied by differential thermal and isothermal reaction. The devitrification of melts was occured in stages, the recognizable amount of CaO was appered at the first step, then proto-C3A was crystallized. The latter showed to occur in both cubic C3A and Ca-ferrite crystallization. Batches lost remarkable amounts of $K_2O$ as a result of volatilization during melting and the solubility of $K_2O$ in the melts was unstable.