Study On Preparation And Properties Of Hydroxyapatite

Hydroxyapatite（HAP）has good biocompatibility and bioactivity,which also has photocatalytic properties in recent years.As a kind of biomaterial,HAP has the advantages of simple synthesis,wide source,easy structure modification and environmental friendliness.Therefore,it has more and more important applications in bioremediation,photocatalytic treatment of wastewater and photocatalytic reduction of CO₂.In this dissentation,HAP nanoparticles were first prepared by the method of biomimetic mineralization,low crystallinity and partial carbonate substitutional HAP nanoparticles were successfully prepared.And in the conditions of different concentrations of Mg²⁺and polyacrylic acid（PAA）,HAP was used to repair enamel.The tooth enamel had the best mechanical strength in the condition of pretreated with200μg/ml PAA solution and then absorbed in HAP nanoparticles prepared at 4.5 m M Mg²⁺concentration.The hardness of tooth enamel after remediation was 1.95 times than that of the tooth enamel without HAP treatment.In this dissentation,HAP was also prepared from waste fish scales by alkali treatment and calcination and was used for photocatalytic degradation of ammonia nitrogen wastewater.With the increase of calcination temperature,the amount of biochar in the sample decreased,and HAP was formed when it was at 600℃.When it was calcined at 800℃for 2 h,the prepared sample has the best adsorption and degradation performance:the maximum adsorption capacity of ammonia nitrogen is1.003 mg/g within 300 min（in terms of N）and the photocatalytic degradation efficiency of ammonia nitrogen is 21%,while the total removal rate of ammonia nitrogen is 41%.Finally,Cu²⁺doped Cu-HAP photocatalyst was prepared by a rapid method in simulated human body fluid.The effect of calcination conditions on the photocatalytic reduction of CO₂ by Cu-HAP were investigated.The results showed that the produce rate of CH₄ and CO in the photocatalytic reduction of Cu-HAP were 1.71 and 9.04μmol·g^-1·h^-1,respectively,which were 3.4 and 8.2 times of the pure HAP.Besides,the produce rate of CH₄and CO in calcined Cu-HAP were 4.75 and 37.74μmol·g^-1·h^-1,respectively,which were 9.3 and 34.1 times of the pure HAP.Meanwhile,all Cu-HAP samples showed high CO selectivity,and the highest CO selectivity of calcined Cu-HAP was 89%.