• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.3
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• pp.96-102
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• 2022

Hydroxyapatite (HAp) was synthesized from calcium hydroxide (Ca(OH)₂) reacting with phosphoric acid (H₃PO₄) in aqueous solution. HAp powders were synthesized from extremely high concentration of precursor solutions over 3 M of Ca(OH)₂ aqueous suspension using modified process parameters such as phosphoric acid (H₃PO₄) pouring rate, aging time and post ball milling process. Regardless of phosphoric acid pouring rate, the DCPD (dicalcium phosphate dihydrate) was formed at room temperature and when heated above 700℃, β-TCP (tricalcium phosphate) was synthesized and the amount reached its maximum at 900℃. When the synthesized powder was sintered at 1150℃, β-TCP, a high temperature impurity phase, remained. The single HAp phase without DCPD was obtained from post ball-milled precipitates followed by 3 day aging. For the ball-milled precipitates even without the aging process, the desired single HAp phase without β-TCP could be obtained by heat treatment above 500℃. The post ball milling process provided a convenient route for HAp synthesis.

• Resources Recycling
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• v.13 no.3
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• pp.3-11
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• 2004

Basic studies have been conducted regarding the crystal formation of hydroxyapatite which was produced in the treatment process of phosphate-containing wastewater using calcium ions as the precipitating agent for its employment as the material for artificial bones. The precipitation of hydroxyapatite were conducted in the synthetic solution which simulating human body fluid for its increased applicability. Ca($NO_3$)$_2$$.$$4H_2$O and ($NH_4$)$_2$$HPO_4$ were employed for the precipitation of hydroxyapatite and its composition was analyzed after drying at 80oC. The thermal behavior of precipitate was investigated by examining the change in its crystalline structure according to the sintering temperature. DTA/TG analysis showed that the escape of moisture from the precipitate occurred at ca. $100^{\circ}C$ and the decomposition of ammonia and the evaporation of lattice water were brought about at around $250^{\circ}C$. X-ray diffraction analysis indicated that the thermally treated precipitate consisted mainly of hydroxyapatite. For dried precipitate, the bonds in the component materials which used for the precipitate formation were observed by FT-IR, and after thermal treatment the major bonds in the precipitate were shown to be $OH^{-}$, $PO_4^{3-}$ , and $CO_3^{ 2-}$ , which were main comprising bonds of hydroxyapatite.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.484-485
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• 2006

The process of coprecipitation of biocomposite hydroxyapatite/chitosan from aqueous solution at low temperature in alkali environnement was examined. We have shown that initially we have the formation of amorphous octocalcium phosphates $(Ca_8(HPO_4)(PO_4)_5,\;nH_2O:\;OCP)$ and the transferring from OCP to amorphous calcium phosphate $(Ca_9(PO_4)_3,\;nH_2O:\;TCP)$, and then from TCP to calcium-deficient hydroxyapatite $(Ca_{10-X}\;(HPO_4)_X(PO_4)_{6-x}(OH)_{2-X}\;:\;ACP)$ and hydroxyapatite $(Ca_{10}(PO_4)_6(OH)_2\;:\;HAP)$. The transformation of ACP to HAP was inhibited in the presence of chitosan. The result suggests that there is an affinity binding between ACP and chitosan and subsequently blocking the active growth site of ACP.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.855-859
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• 2000

An application of synergistic solvent extraction for the etermination of trace lithium in sea water has been studied by forming an adduct complex of thenoyltrifluoroacetone (TTA) and trioctylphosphine oxide (TOPO) in a solvent. The interference by major constituents in sea water was eliminated by phosphate precipitation. Ex-perimental conditions such as solution pH, concentrations of TTA and TOPO etc. were optimized in synthetic sea water with similar compositionto its natural counterpart. To eliminate the interference, 1.38g of ammoni-um dihydrogen phosphate and 2.5 mL of ammonia water were added into 100 mL of thediluted solution at $60^{\circ}C$ to form the phosphate precipitates of Ca2+ and Mg2+ ions. After the pH of this filtrate was adjusted to 8.0, 10.0 mL of m-xylene containing 0.1 M TTA and 0.05 M TOPO was added to the solution in a separatory funnel, and the solution was shaken vigorously for 20 minutes. The solvent was separated from the aqueous solution, and 20 uL of m-xylene solution was injected into a gaphite tube to measure the absorbance by GF-AAS. The detection limit was 0.42 ng/mL. Lithium was determined within the range of 146 to 221 ng/mLin Korean coast-al sea waters, and the recoveries in the spiked samples were 94 to 106%.

• Clean Technology
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• v.16 no.4
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• pp.258-264
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• 2010

This study estimated the possibility of phosphate removal characteristics to utilize EAF(electric arc furnace) slag as submarine cover material. The major phosphate removal mechanism was a certain formation of HAP precipitation occurred by the ionization reaction between $Ca^{2+}$ and $OH^-$, which were leached from the EAF Slag. Another phosphate removal mechanism was the adsortion of EAF slag surface. As a result of $PO_4{^-}-P$ removal characteristics using continuous column reactor, $PO_4{^-}-P$ concentration decreased rapidly after 3 days and 10 days later, it show under 0.5 ppm. The result as applied in real sea water, shows that the phosphate removal effects were 93~98% by the subaqueous sediment removal using the EAF slag. In conclusion, EAF slag is useful in $PO_4{^-}-P$ removal and control and it is possible to use without additional process like crush and selection.

• Journal of Soil and Groundwater Environment
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• v.12 no.6
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• pp.100-106
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• 2007

The objective of this study was to evaluate the efficiency of $(NH_4)_2HPO_4$, $Na_2HPO_4{\cdot}12H_2O$, $CaHPO_4{\cdot}2H_2O$, $Ca(H_2PO_4)_2{\cdot}H_2O$ and $H_3PO_4$ for the stabilization of soils contaminated with multi-metals containing Pb, Cd and As. The application rate of stabilizers to soils was determined based on $PO_4/Pb_{total}$ molar ratio of 0.5, 1, 2, 4. The results of Korea Standard Test and TCLP (EPA Method 1311) showed the reduction of metal leachabilities below the regulatory limits for Pb and Cd when $H_3PO_4$ and $Ca(H_2PO_4)_2{\cdot}H_2O$ were applied. However, stabilization efficiency for Cd was low and in case of As leaching concentration increased rather. It is considered that $PO_4$ reacted effectively $Pb^{2+}$ due to leaching Pb under low pH condition created by adding $H_3PO_4$. Accordingly Pb was stabilized by dissolution and precipitation of hydroxypyromorphite. From the change of metals fraction using sequential extraction procedure when $H_3PO_4$ applied as a stabilizer, we confirmed that residual fraction increased more than 60% and this result was accorded with XRD analysis that detected only hydroxypyromorphite peak in $H_3PO_4$.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.28-39
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• 2016

Struvite (MgNH₄PO₄ ⋅ 6H₂O) and hydroxyapatite (HAP, Ca₁₀(PO₄)₆(OH)₂) precipitation in urine-separating toilets (NoMix toilets) causes severe maintenance problems and also reduce the phosphate and calcium content. Application of urine separating technique and extraction of by-products from human urine is a cost effective technique in waste water treatment. In this study, we extract urine calcite from human urine by batch scale method, using urease producing microbes to trigger the precipitation and calcite formation process. Extracted urine calcite (calcining at 800℃) is a potential adsorbent for removal of heavy metal(loid)s like (Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, Zn²⁺ and As³⁺) along with additional leaching analysis of total nitrogen (T-N), phosphate (T-P) and chemical oxygen demand (COD). The transformations of calcite during synthesis were confirm by characterization using XRD, SEM-EDAX and FT-IR techniques. In additional, the phosphate leaching potential and adsorbate (nitrate) efficiency in aqueous solution was investigated using the calcinedurine calcite. The results indicate that the calcite was effectively remove heavy metal(loid)s lead up to 96.8%. In addition, the adsorption capacity (q_e) of calcite was calculated and it was found to be 203.64 Pb, 110.96 Cd, 96.02 Zn, 104.2 As, 149.54 Cu and 162.68 Ni mg/g, respectively. Hence, we suggest that the calcite obtain from the human urine will be a suitable absorbent for heavy metal(loid)s removal from aqueous solution.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.371-376
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• 2007

The features of precipitating reaction of fluorine have been examined under several aquatic conditions by employing calcium ion as a precipitant. Based on MINTEQ program, fluorine was found to exist in the forms of $H_2F_2$ and HF in strong acidic environment and change into $F^-$ with increasing pH. In the experimental condition, the precipitating reaction of fluorine progressed rapidly within a few minutes after the reaction started and reached its equilibrium in 10 minutes. As the addition of precipitant was increased, removal of fluorine by the formation of precipitate was promoted and its was also enhanced by the rise of pH. The precipitating reaction of fluorine was impeded when its initial concentration was low and X-ray analysis showed that the crystalline structure of precipitate was mainly $CaF_2$ with partly NaF. Coexisting phosphate in solution influenced the fluorine removal by impeding the precipitate formation and similar effect was found when metallic ion such as $Zn^{2+}$ was present with fluorine.

• Advances in nano research
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• v.4 no.4
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• pp.295-307
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• 2016

The present research work reports a low temperature ($40^{\circ}C$) chemical precipitation technique for synthesizing hydroxyapatite (HAp) nanoparticles of spherical morphology through a simple reaction of calcium nitrate tetrahydrate and di-ammonium hydrogen phosphate at pH 11. The crystallinity of the single-phase nanoparticles could be improved by calcinating at $600^{\circ}C$ in air. Thermogravimetric and differential thermal analysis (TG-DTA) revealed the synthesized HAp is stable up to $1200^{\circ}C$. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies confirmed the formation of spherical nanoparticles with average size of $23.15{\pm}2.56nm$ and Ca/P ratio of 1.70. Brunauer-Emmett-Teller (BET) isotherm of the nanoparticles revealed their porous structure with average pore size of about 24.47 nm and average surface area of $78.4m2g^{-1}$. Fourier transform infrared spectroscopy (FTIR) was used to confirm the formation of P-O, OH, C-O chemical bonds. Cytotoxicity and MTT assay on MG63 osteogenic cell lines revealed nontoxic bioactive nature of the synthesized HAp nanoparticles.

• Journal of Animal Science and Technology
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• v.45 no.3
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• pp.491-498
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• 2003

The purpose of this study is to observe purification and properties of osteopontin(OPN) from bovine milk. The purification of osteopontin from bovine milk was performed by using ion-exchange and hydrophobic chromatography. SDS-PAGE analysis revealed that the protein migrated at Mw. 60,000. NH2-terminal sequence analysis of the first seven amio acids revealed the protein to be identical to that previously reported for bovine OPN. 35-wk-old chickens, including 3 Single Comb White Leghorn (SCWL), were used to produce egg yolk antibody(IgY) against OPNas a antigen. However, the anti-OPN antibody activities determined by ELISA. Immunological assy of OPN in milk was performed using radial immunodiffusion test based on the standard curve of pure OPN. The radial precipitation lines of four different milk samples indicated that the concentrations of OPN in the milk samples were within the range of 31.7 to 39.7${\mu}g$/ml. On inhibition with OPN on precipitation of calcium phosphate, OPN was slightly higher than casein phosphopeptide(CPP) and poly-glutamic acid.