Preparation, Composition Comparative Crystal Chemistry And Absorbing F～- Action Of Apatite (AP)

Because one-valence ations in the apatite (AP) occupy the "column" in structure, and cationshave two different crystal chemistry circumstances in Ca (1) and Ca (2) site, the kind of specialstructure brings considerably interaction of absorption and ion exchange to different valenceexternal-ations. Taking full advantage of the function, AP manufactured for filter of removing F isnot restricted within temperature, pressure, pH, contents and flow, has a wide-ranging usingprospect and low production cost, can produce immobilization, and is with no-toxicity andnon-secondary pollution. Therefore, AP will become the most valued green environmentprotection material. In this paper, composition comparative crystal chemistry research method isfirst used to study the relationship of absorbing Faction with crystal chemistry characteristics of APby using of XRD, FT-ER, TEM and DTA/TG. The main contents of the paper are as follows. The apatite (AP) with end-member cations, the apatite solid solutions [M-M1 AP] withdivalent cations substitution, the fluorapatite (FAP) and the chlorapatite (CLAP) with end-memberations, the apatite solid solutions [Xi-X2 AP] with column-ions substitution were synthesizedthrough ' solid-phase reaction method' in inert gas. The appetite (AP) with different valent cationssubstitution, the hydroxyapatite (HAP) with different molar ratio (R) of Ca to P and the variousCO32" substitution hydroxyapatite solid solutions (CHAP) with granular-shortcylinder shapes wereprepared by a 'Sol-Gel process' . The CHAP whisker with controlled average ratio of length towidth were prepared by 'one-phase co precipitating method in two-steps temperature' . Usingcollagen protein as the template-mediated, the flake-like CHAP was synthesized through' biomimetic synthesis method'.Influence of composition in cations site and column-ion site on apatite crystal chemistrycharacteristics-lattice-parameters, degree of lattice defect and [PO4] tetrahedral distortion indexhave been investigated by XRD and FT-IR.To the hydroxyapatite (HAP) with different Rs , when 1.2<=R<=2.3, the specific surface area (As,) and the degree of lattice defect increases. (Tr) , but the crystalline size (rA,r(221),rR) ,the morphology index (MI) and the crystalline (CD) decrease with the increasing of stoichiometric deviating, when R =2.5, the degree of lattice defect increases regularly, but the crystalline size and the degree of crystallization increase reversibly. The lattice defect model demonstrated by the measurement of average crystalline density and analysis of phase tranversion is that (1) defect type of the Ca- deficient HAP (R<1.67) is vacant defect, (2)defect type of the Ca surplus HAP (R<1.67) is inset defect and (3)defect type of the HAP (R=2.5) is composite defect.When calcinations temperature (Tc) is < 800 #, the all HAPs are with good thermal stability. When Tc is >= 800#,the Ca-deficient HAP occur dehydroxy-decomposition, into Ca3(PO)2(TCP phase); the Ca-stoichiometric HAP(R=1.67) and the Ca-surplus HAP have good thermal stabilization ,and exist without so much as dehydroxy-decomposition at 1500X2. Based on the natural diffusion theory of Schottky-Frenker, the natural diffusion coefficient is expressed by theAequation: D = y0(3a2o + 2C0)exp, which demonstrates that the different lattice defectRTtypes result in differences of phase tranversion of HAPs with various Rs. In a successive non-equilibrium solid solution decomposition way, CO32" escapes from the CHAP at 150~800"C, meanwhile crystallization degree and re-crystalline size increase. Because of the difference of the ' lattice defect types and the OH" contents in column structure , when O32"<3.34 %, the CHAP occurs dehydroxy-decomposition at 776,when JFCO32">3.34 % , the CHAP can not occur dehydroxy-decomposition at 150~1500.By means of Gauss function fitting and substitution index (SI) determinnating, the model of AB mixed-type substitution structure of CHAP is deduced. [COyOH] tetrahedral-coordination is substi...