• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.887-890
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• 2009

Hydroxyapatite (HAp)-based materials have attracted considerable attention on account of their excellent stability and recrystallization. Nanoscale HAp powders with a mean particle size of 200 nm were used to regenerate the enamel layers of damaged teeth. An artificially scratched tooth was immersed in a nanoscale HAp powder suspension in d.i. water (HAp of 70 wt%) at 37 ${^{\circ}C}$ for a period of 1~3 months. SEM and AFM showed that the scratched surface was ultimately inlaid with HAp after three months and the roughness increased from 2.80 to 5.51. Moreover, the hardness of the neo-generated HAp layer on the crown was similar to that of the innate layer. $Ca^{2+}$ and ${PO_4}^{3-}$ ions from the HAp powders dissolved in d.i. water were precipitated on the tooth to produce cemented pasteson the enamel surface due to its high recrystallizing characteristics, resulting in a hard neo-regenerated HAp layer on the enamel layer. This nanoscale HAp powder solution might be used to heal decayed teeth as well as to develop tooth whitening appliances.

• Journal of Navigation and Port Research
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• v.36 no.6
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• pp.459-463
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• 2012

In the present study, experiments have been performed to investigate the effects of the type of adsorbent, pH, and ionic strength on the adsorption of nutrients (nitrate and phosphate in artificial solution) onto the dredged sediment from a coastal fishery. In addition, this study aims to evaluate the possibility of removing the nutrients from the water using the dredged sediment. In the adsorption experiments of the nutrients, the reactions were completed within 10 minutes using ${NO_3}^-$-N($100{\mu}M$, 10mM) and ${PO_4}^{3-}$-P($100{\mu}M$, 10mM). In the steady state, 61% and 77% of the initial amounts were removed respectively for $100{\mu}M$ ${NO_3}^-$-N and $100{\mu}M$ ${PO_4}^{3-}$-P. The thermal treatment of the dredged sediment at $900^{\circ}C$ was not helpful to increase the removal efficiencies of the nutrients. Additives such as CaO and MgO dropped the removal efficiency of ${NO_3}^-$ to 0%, but increased that of ${PO_4}^{3-}$ up to 98%. Adsorption isotherms of ${NO_3}^-$ and ${PO_4}^{3-}$ could be explained by the Freundlich equation ($R^2$>0.99). The adsorption reaction was little influenced by the pH and ionic strength. Based on the results showing short reaction time and considerably high removal efficiencies of the nutrients, it is proposed to apply the dredged sediment from a coastal fishery to removing nutrients such as nitrate and phosphate in the water.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.5
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• pp.437-442
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• 2010

This work was initiated both to maximize purity of calcium fluoride sludge and to minimize water content in the settled sludge. The sludge was produced in the process of fluoride removal of semiconductor wastewater by the addition of $Ca^{2+}$ ion. Fludized bed reactor(FBR) using calcium fluoride as a seed was adapted. Optimum pH and molar ratio of $Ca^{2+}/F^-$ were determined in lab-scale study. The experimental results showed that fluoride removal was increased as pH and molar ratio of $Ca^{2+}/F^-$ increased, with the best removal of 79.8% in an optimum condition. In the optimum point of fluoride removal, very low ${PO_4}^{3-}$-P removal of 9.3% was observed. It indicates forming $CaF_2$ crystal of high purity, when side reaction of calcium with phosphate was minimized. In addition, water content of settled sludge was 19.3%, which is relatively low compared to other fluoride removal processes. Consequently, the FBR process proposed in this study was very effective in fluoride removal, producing good sludge of high purity and less water content.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.300-304
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• 1999

To tap the feasibility of exploiting the 2$^{nd}$ phases as flux-pinning centers in the (Bi,Pb)$_2Sr_2Ca_2CuO_{10}$ superconductor, the size and the distribution of the precipitates have been controlled by changing reaction temperature and time, oxygen partial pressure Po$_2$ and annealing condition. Various annealing heat treatments were also conducted on the as-received 61 filament Bi-2223 tapes with Bi$_{1.8}Pb_{0.4}Sr_2Ca_{2.2}Cu_3O_8$ starting composition and annealed specimen were analyzed with XRD, SEM, EDS and TEM.. The grain size of (Ca,Sr)$_2$(BiPb)O$_4$ or Bi$_{0.5}Pb_3Sr_2Ca_2CuO_{\delta}$ was controllable by optimizing the heat treatment condition and critical current density (J$_c$) showed dependence on the size of the 2$^{nd}$ phases.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.84-89
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• 2009

The turbid/translucent, near colorless(milky) metamorphic sapphire samples from Sri Lanka have been characterized after the heat treatment in $N_2$ at $1650^{\circ}C$. As-received sapphire specimens became bluish-colored and exhibited more clarity after the heat treatment. It was found that the color change at inclusions zoning region is attributed by the dissolution. As received samples contain the micro/nano inclusions such as rutile($TiO_2$), ilmenite($FeTiO_3$), spinel($MgAl_{2}O_{4}$)/ulvospinel($Fe_{2}TiO_{4}$) and apatite($Ca_5(PO_4)_3$), which were dissolved by the heat treatment and form the blue color through $Fe^{2+}/Ti^{4+}$ charge transferring. The microstructures become different because as the dissolution of apatite($Ca_5(PO_4)_3(OH,F,Cl)$) in alumino silicates($Al_{2}SiO_{5}$) occurred, resulting in morphological change with the appearance of(Ca, Mg, Al) silicate on the surface. Both as-received and heat treated samples showed the rhombohedral crystal structure of $Al_{2}O_{3}$.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.994-999
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• 1997

The sintering properties of hydroxyapatite isolated from tuna bone and hydroxyapatite-containing wollastonite sintered by solid-state reaction was investigated. As the sinterability of hydroxyapatite dependent upon the particle size by dry milling, it showed a sintering. But the hydroxyapatite-containing wollastonite was appeared good sinterability. On X-ray measurements, the major phases of hydroxyapatite-containing wollastonite by solid state reaction at $1250^{\circ}C$ were identified as hydroxyapatite and pseudowollastonite(${\alpha}-CaSiO_3$). And the phases appeared as whitlockite [$Ca_3(PO_4)_2$] by decomposition of hydroxyapatite at higher temperature above $1250^{\circ}C$. The shapes of microstructure on SEM images changed from porous to dense bulk by elevating temperature. The mean bending strength of hydroxyapatite-containing wollastonite sintered by solid-state reaction at $1300^{\circ}C$ was about 18 MPa, it was close to the cancellous bone's maximum strength, 20 MPa.

• Korean Journal of Soil Science and Fertilizer
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• v.19 no.3
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• pp.217-221
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• 1986

A column test was conducted to find out the effect of application of slaked lime, calcium sulfate, calcium superphosphate, and phosphoric acid on the solubility of lead in soil. The soil was adjusted to 310.8 ppm concentration of Pb and applied with amounts of calcium equivalent to 600, 1000, 2000 ppm as slaked lime; sulfate 144, 288, 432 ppm as calcium sulfate; phosphate 95, 190, 285 ppm as calcium superphosphate and phosphoric acid, respectively. The results obtained are as follows: 1. The increasing application of improvement agents reduced the amounts of water soluble Pb in soil. Phosphoric acid was the most effect among to the treatments. 2. The slaked lime treatment has the highest pH of soil and the lowest at the phosphoric acid one. The soil Eh has a reverse tendency the soil pH. 3. Water soluble Ca, $PO_4$ and $SO_4$ contents increased with increasing application amounts of improvement agents in soil. 4. $1N-NH_4$ OAC soluble Pb content in soil was a decreasing tendency in the order of calcium superphosphate, phosphoric acid, slaked lime, calcium sulfate and control after experiment.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.130-132
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• 1996

It is well known when porous calcium phosphate ceramics are used as a bone graft substitute, new tissues or blood vessels are grown into the porous implant due to their excellent biocompatibility. In this study, the ${\beta}$-crystalline form of calcium metaphosphate, $Ca(PO_{3})_{2}$ is prepared by the controlled thermolysis of monocalcium phosphate, $Ca(H_{2}PO_{4})_{2}$. The diameter of cylindrical pores formed during cooling was controlled by a holding time at the melting point of a monocalcium phosphate and by the change of a recrystallization temperature, to obtained the most appropriate size (about $200{\mu}m$) of pores. It was observed that the increasing holding time at the melting point of monocalcium phosphate results in the decreases of pore sizes.

• Microbiology and Biotechnology Letters
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• v.9 no.2
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• pp.51-57
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• 1981

1,2-propanediol-utilizing yeast, Y-1-4, was isolated from sludge sample by the enrichment culture technique. The product produced from 1,2-propanediol by the selected strain was identified as lactic acid by paper chromatography and infrared absorption spectrum. The strain assimilated ethanol, 1,2-propanediol, glycerine and glucose, but it produced lactic acid from 1,2-propanediol used as the sole carbon source. Under optimal conditions, the strain Y-1-4 was cultured with shaking at 3$0^{\circ}C$ for 4days in the medium containing 1,2-propanediol 20.0g, NH$_4$Cl 5.0g, KH$_2$PO$_4$ 1.0g, MgSO$_4$.7$H_2O$ 0.5g, FeSO$_4$.7$H_2O$ 0.25g, yeast extract 0.4g, CaCO$_3$ 3. 0g and tap water to one liter, and then the yield of lactic acid was about 12. 1g per liter of the culture broth.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.3
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• pp.223-231
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• 1999

This study was carried out to investigate the factors influencing water quality of the river (Mankyeong River) and groundwater in controlled horticulture region from 1994 to 1998. Water quality of Mankyeong River was monitored at 13 sites along main stream for 6 months from April to September from 1994 to 1997. Monthly average concentrations of $NH_4-N$, $SO{_4}^{2-}$ and $Cl^-$ were highest in April, while that of $NO_3-N$ was highest in August. Monthly average concentrations of COD was highest in September Concentrations of $NH_4-N$ and $SO{_4}^{2-}$ in many sites of Mankyeong River exceeded the water quality criteria of agricultural water for irrigation. Water quality of Mankyeong River was not suitable for the irrigation source excepted the sites such as Hari, Gosan and Soyang stream. The floodgates of Mokcheon, Yocheon, Jeonju and Samcheon streams were rapidly polluted by the municipal sewage, otherwise the Iksan stream was rapidly polluted by the sewage of swine. The sum of inorganic ion concentrations in Mankyeong River was highest at floodgate of Yocheon due to the sewages municipal and industrial. The order of the major anions and canons concentration in Mankyeong River- stream were $SO{_4}^{2-}$ > $Cl^-$ > $NO{_3}^-$ > $PO{_4}^{3-}$ and $Na^+$ > $Ca^{2+}$ > $NH{_4}^+$ > $Mg^{2+}$ > $K^+$, respectively. The geoundwater quality at controlled horticulture region was surveyed 4 sites from 1994 to 1998. Concentrations of $NH_4-N$ and $NO_3-N$ were lower at the deeper groundwater. However there was no difference between the concentrations of $SO{_4}^{2-}$ and $Na^+$, and the groundwater depth below 15m. Contents of $NH_4-N$, $NO_3-N$, $PO{_4}^{3-}$, $SO{_4}^{2-}$, $Na^+$ and $Cl^-$ in groundwater were the highest at dry season. Nitrate-N level, exceeded $20mg\;l^{-1}$, the critical level for agricultural usage, at Yongjinmyeon Wanju and $PO{_4}^{3-}$ concentration were higher at Seogtandong Iksan than the other places.