Synthesis Of Hydroxyapatite By Chemical Precipitation Method And Its Application In Dye Degradation

Hydroxyapatite(Ca₁₀（PO₄）₆（OH）₂,HAP) crystal belongs to symmetric L₆PC andP63/m space group for hexagonal crystal structure. Artificially synthetic HAP can bewidely used as environmental material. HAP-Fe³⁺,which is made by loading Fe³⁺ontoHAP, was used as catalyst of fenton system, efficiently oxidating the dyes. In thisstudy, methylene blue and crystal violet were used as reaction substrate to study thecatalytic oxidization performance of this kind of fenton system of HAP-Fe³⁺/H₂O₂.The main contents of this research include the following:（1） Expandedgraphite（EG） was made and analyzed by XRD, FT-IR, TEM and BET;（2） HAP isprepared by chemical precipitation in the presence of EG and analyzed by XRD, SEM,FT-IR, SEM, TEM and BET;（3） Hydroxyapatite was used as catalyst of fentonreaction catalyst by loading Fe³⁺onto HAP, then the catalyst was analyzed by XRD,FT-IR, TEM and BET;（4） The influence of reaction temperature, initial concentrationof dyes, pH value of initial solution, dose of Catalyst and oxidant etc. on theoxidization property of dyes are analysed;（5） Make a study of the dynamic equationsof reaction process.The results of the study show that:（1） The main XRD diffraction peaks and theinfrared absorption peaks consistent with the standard spectrum of hydroxyapatite, noother diffraction peaks founded, indicating that the synthetic sample is hydroxyapatite;（2） In the presence of EG, the infrared diffractogram of the synthetic sample can showthe infrared absorption peaks of PO3-4completely;（3） When pH＞10or pH＜5,absorption of HAP to Methylene blue is better. When pH is close to8, however, Theadsorption efficiency of HAP to Methylene blue is low;（4） When HAP-Fe³⁺is2g/Land pH value is8and H₂O₂is10mL/L, the oxidization decomposition ratio of40mg/L Methylene blue could reach to96.9%after80min; when HAP-Fe³⁺is1g/Land pH value is9and H₂O₂is20mL/L, the oxidization decomposition ratio of40mg/L Crystal violet could reach to96.6%after40min;（5） The kinetics model of dyes onto fenton-like reagent HAP-Fe³⁺/H₂O₂were investigated. The oxidizationprocess of dyes can be better described by the pseudo-second-order model（R2>0.98）.