Hydroxyapatite Modified And Photocatalytic Degradation Of Dyes In Research

Hydroxyapatite(Ca10(PO4)6(OH)2,HAP) crystal belongs to symmetric L6PC and P63/m space group for hexagonal crystal structure. Synthetic HAP can be widely used as environmental material. The compound catalytic material(Ti-HAP) combined with the hydroxyapatite, doped TiO2, has high activity under UV irradiation and efficient in degradation of dyes. The photocatalytic property of HAP and Ti-HAP is studied with azo dyes, Methyl Orange, and anthraquinone dyes, Reactive Brilliant Blue K-3R, as the degradation substrate.The main contents of this research include the following: (1) HAP is prepared by chemical precipitation while Ti-HAP is prepared by hydrothermal method, and they are analyzed by XRD, SEM, FT-IR, SEM and DSC instruments. (2) The effects of heat treatment temperature of HAP, hydroxyapatite dosage, air aeration and pH value of initial concentration etc. on the photocatalytic degradation of HAP in Methyl Orange and Reactive Brilliant Blue K-3R are investigated. (3) The influence factors of hydrothermal synthesis temperature, titanium-doped proportion, initial concentration of dyes, pH value of initial solution etc. on the photocatalytic degradation of Ti-HAP in Methyl Orange are analysed. (4) Finally, make a study of the dynamic equations of photocatalytic degradation process and the mechanism of degradation preliminarily.The results of the study show that: (1) The main XRD diffraction peaks and the infrared absorption peaks consistent with the standard spectrum of hydroxyapatite, no other diffraction peaks founded, indicating that the synthetic sample is hydroxyapatite; (2) In addition to generating anatase TiO2 coated HAP in the powder after hydrothermal synthesis of titanium-doped, there are changes in XRD and FT-IR absorption peak position and peak shape; (3) The adsorption quantity of Methyl Orange in HAP and Ti-HAP is weaker relative to Reactive Brilliant Blue K-3R; (4) When HAP(200℃) dosage is 4g/L and the air aeration is 300L/h and pH value is 6, the degradation removal ratio of 10mg/L Methyl Orange could reach to 84% after 4h while the degradation removal ratio of 100mg/L Reactive Brilliant Blue K-3R could reach to 74% after 3h; (5) When Ti-HAP (400℃) dosage was 4g/L, the air aeration was 300L/h and pH value is 6, the degradation removal ratio of 50mg/L Methyl Orange could reach to 78% after 4h while the degradation removal ratio of 100mg/L Reactive Brilliant Blue K-3R could reach to 89% after 3h; (6) Ti-HAP has higher degradation rate compared with HAP, which is due to Ti-doped, not only affect the structure of HAP, but also formed TiO2 with a high catalytic activity; (7) The photocatalytic degradation process of dyes in HAP and Ti-HAP followed the Langmuir-Hinshelwood first-order kinetics model with good correlation(R2>0.97); (8) The mechanism of photocatalytic degradation may be to produce the hydroxyl radicals and oxygen radicals, in uv irradiation and catalysis of HAP and Ti-HAP, which can oxidate the chromophore groups of dyes.The research shows that hydroxyapatite and hydroxyapatite doped titanium have good effects for azo dyes and anthraquinone dyes and this is a good development prospect of degradation.