Study On Synthesis Of Hydroxyapatite And Their Adsorption Of Organic Matter

Hydroxyapatite （HAP） is a function material, which is basically consistent with theinorganic composition and structure of human bone; it has good biocompatibility and active.Because hydroxyapatite has good adsorption effect, which can remove the metal ion and someorganic matter from wastewater under the specific conditions, it can achieve the function ofwastewater treatment.In this experiment, not calcined hydroxyapatite （HAP） and carbonated hydroxyapatite（CHAP） were synthesized by the method of sol-gel. Fourier transform Infared spectroscopy（FT-IR）, X-ray diffraction （XRD）, Scan electron microscopy （SEM） and Surface areameasurement （BET） were used to characterize the two types of hydroxyapatite. The resultshows that, we can see that the carbonated hydroxyapatite successfully mixed with CO₃^2-fromthe IR characterization. Compare with the XRD standard card of hydroxyapatite, we can see thesynthetic sample is hydroxyapatite. The surface area of the synthetic hydroxyapatite andcarbonated hydroxyapatite were121.75and129.91m²/g respectively, the pore volumes were0.44and0.53cm³/g respectively, and the particle sizes were14.62and15.60nm respectively,which belongs to the nanometer level particles. The surface areas of the two hydroxyapatiteswere larger than other samples, and which is the porous structure. So the pollutants are easilyadsorbed on the hydroxyapatite surface.If the organic matter exist in wastewater, the aerobic microorganism in the water whichcan degrade the organic pollutant, and consume the dissolved oxygen at the same time. If theorganic pollutant is too much, the water will appear the phenomenon of dissolved oxygendeficit and even without oxygen, which can make water quality deterioration and endanger theaquatic creatures and human health. There have been reported in the literature thathydroxyapatite has the good adsorption properties. In this paper, the calcination hydroxyapatite,not calcined hydroxyapatite and carbonated hydroxyapatite were as adsorbents, the three kindsof hydroxyapatite adsorbed xylenol orange, not calcined carbonated hydroxyapatite adsorbedAcid Blue7and Basic Green4, and calcination hydroxyapatite adsorbed phenol, we mainlyinvestigated the affect of different solution pH, different organic matter initial concentrationand different reaction times, and explore the adsorption mechanism simply. The results showed that: the adsorption amount of xylenol orange onto the three kinds of hydroxyapatite firstlyincreased and then decreased with the pH increasing, and the adsorption effect was best about atpH8.00, xylenol orange adsorbed onto hydroxyapatite by chemical adsorption. The adsorptioncan be described by Langmuir isotherm, and the adsorption ability of xylenol orange ontohydroxyapatite was not calcined hydroxyapatite> not calcined carbonated hydroxyapatite>calcination hydroxyapatite. The adsorption process can be represented by pseudo-second-orderkinetic model, and the equilibrium can be achieved at120min. Through the determination ofUVDRS, xylenol orange adsorbed onto the three kinds of hydroxyapatite by the Ca²⁺of itssurface, the adsorption is chemical adsorption. The adsorption amount of Acid Blue7onto notcalcined carbonated hydroxyapatite decreased with the pH increasing, so at about pH6.00, theadsorption effect of Acid Blue7onto not calcined carbonated hydroxyapatite was best. Theadsorption amount of Basic Green4onto not calcined carbonated hydroxyapatite increased andthen went to equilibrium with the pH increasing, so the adsorption of Basic Green4onto notcalcined carbonated hydroxyapatite is best in the range of alkalinity, and the not calcinedcarbonated hydroxyapatite was apt to adsorb the basic dye. The adsorption of Acid Blue7ontonot calcined carbonated hydroxyapatite followed the Freundlich isotherm, and the adsorption ofBasic Green4followed the Herry isotherm. The process of adsorption of Acid Blue7and BasicGreen4can be described by pseudo-second-order kinetic model, and the equilibrium can beachieved at120min. Through the determination of UVDRS, The process of not calcinedcarbonated hydroxyapatite adsorbing Acid Blue7and Basic Green4is physical adsorption,which was got by Van der Waals force. The adsorption amount of phenol onto calcinationhydroxyapatite increased with the pH increasing, and the adsorption amount increasedstraightly when the pH>7, so the hydroxyapatite can effectively remove phenol in alkaline.Langmuir isotherm can be used to describe the adsorption of phenol onto hydroxyapatite.Pseudo-second-order kinetic model can represent the adsorption of phenol onto hydroxyapatite,and the equilibrium can be achieved at120min. Through the determination of UVDRS, Theprocess of calcined hydroxyapatite adsorbing phenol is physical adsorption.