Preparation And Properties Of The Hydroxyapatite

Hydroxyapatite (HA) as a new type of nano-biological materials has been widespread concern at home and abroad in recent years. Hydroxyapatite-dimensional chemical structure of the rules and good biocompatibility make it in the catalysis, protein separation, high-profile areas such as bio-sensing for sensitive biological detection and sensor miniaturization has opened up new applications road. Based on the strong adsorption of hydroxyapatite and unique multi-adsorption sites, HA has been used to deal with waste water containing heavy metal ions, contaminated soil, etc.This paper outlined the review part of the unique stereochemistry of hydroxyapatite bodies, compared with several conventional method of preparing hydroxyapatite, described in detail the adsorption mechanism of heavy metal ions by hydroxyapatite and discussed influence factors. Hydroxyapatite application in biological sensing had been looked forward. Experimental studies include the following elements:1. HA modified platinum electrodes for glucose biosensorA novel glucose biosensor was constructed by immobilizing the glucose oxidase(GOD) on hydroxyapatite(HA)-polyvinyl alcohol(PVA) composite film electrodeposited on platinum electrode and applied to the highly selective and sensitive determination of glucose. The GOD adsorbed onto the HA-PVA composite film exhibits a pair of well-defined nearly reversible redox peaks and fine catalysis to the oxidation of glucose. The results demonstrated that with the cooperation of HA-PVA and Nafion, which can enhance the electrochemical activity of GOD and promote electron transfer, the composite film played an important role in enhancing the stability and sensitivity of the biosensor, the decreased reduction current was linear with the concentration of glucose in the range of 0.02- 0.52 mM. The results demonstrated that this modified electrode can achieve highy sensitive determination of glucose.2. HA modified TiO₂ for glucose biosensorA glucose biosensor was constructed by immobilizing the glucose oxidase(GOD) on hydroxyapatite prepared by sol-gel method on TiO₂ prepared by anodic oxidation to the highly selective and sensitive determination of glucose. In this experiment,we optimized the best work voltage of this composite electrode by chronoamperometry of glucose in the solution and tested the sensor stability and reproducibility. Within the Nafion/GOD-HA-PVA/TiO2/Ti structure, there was a good synergy between hydroxyapatite, titanium dioxide nanotubes and Nafion, to keep the activity of GOD. This composite electrode showed excellent catalyst for the oxidation of glucose at -0.42V voltage.3. HA adsorption of Zn²⁺ in aqueous solutionIn this experiment, we prepared hydroxyapatite by liquid phase precipitation and studied the adsorption of Zn²⁺, mainly on the initial concentration of Zn²⁺, temperature, pH, and reaction time on removal efficiency and adsorption mechanism of HA.Experimental results showed that HA synthesized by liquid phase precipitation was a good new adsorbent to the adsorption of Zn²⁺. The optimized adsorption conditions for water-soluble Zn²⁺ were as following: pH 6.5, reaction time 50min, the temperature 35℃. HA on the adsorption of heavy metal ions in solution can be divided into roughly the beginning of the late stage of the surface adsorption and ion exchange adsorption.