为了提高羟基磷灰石的分散性，通过水热法合成羟基磷灰石粉体。通过添加柠檬酸提高样品的分散度、降低晶粒尺寸，从而提高在模拟水样中的除氟效率。通过单因素试验和响应面法对羟基磷灰石的水热合成工艺条件进行主要参数优化，并利用红外光谱、扫描电镜、能量色散X射线光谱、比表面积及孔隙分析和X射线衍射仪等表征了不同柠檬酸添加比例下水热合成羟基磷灰石。结果表明，柠檬酸的加入会显著影响羟基磷灰石在纳米尺度下的微观形貌。利用Box-Behnken设计的3因素3水平响应面试验确定水热法合成羟基磷灰石的最佳参数为：水热温度147 ℃、水热时间8 h、柠檬酸添加量0.5%，在最佳工艺条件下，成功得到高分散度的纳米羟基磷灰石，针对模拟水样（氟离子质量浓度为6 mg/L）除氟效率达44.6%，除氟容量为2.678 mg/g，高于同等测试条件下的市售羟基磷灰石测试值（1.437 mg/g）。吸附过程的热力学研究表明，Langmuir等温模型拟合效果要优于Freundlich模型。计算热力学参数可知，所制备的羟基磷灰石对氟离子的吸附是自发(ΔG0＜0)、放热(ΔH0＜0)、熵增(ΔS0＞0)的过程。羟基磷灰石对氟离子的吸附符合准二级反应动力学过程。通过造粒成型及连续吸附装置对所制羟基磷灰石样品进行评价，出水氟离子质量浓度连续9 d保持在1.0 mg/L以下，该吸附剂具有良好除氟效果。

In order to improve the dispersibility of hydroxyapatite,hydrothermal method with citric acid as chelating agent was used to prepare hydroxyapatite with improved dispersibility and citric acid was added to improve the dispersion of the sample,reduce the grain size,and adsorb fluorine ions in simulated water samples. The main parameters of hydrothermal synthesis of hydroxyapatite were optimized by single factor test and response surface method. Hydroxyapatites with different ratio of citric acid were characterized by five techniques such as：X-ray Diffraction (XRD),Fourier Transform Infrared Spectroscopy (FT-IR),Scanning Electron Microscope (SEM),Nitrogen Adsorption/Desorption Experiment and Energy Dispersive Spectrometer (EDS). The results show that the addition of citric acid will significantly affect the micro morphology of hydroxyapatite in nano scale. Box-Behnken design with three-levels and three-factors has been applied to determine the optimal parameters such as hydrothermal time (4-8 h),temperature (140-160 ℃),citric acid dosage (0.5%-1.5%) on removal of fluoride from simulated solution. The results show that the optimal conditions are 147 ℃ of hydrothermal temperature,eight hours of hydrothermal time,and 0.5% of citric acid addition. Under the best process conditions,nano hydroxyapatite with high dispersion is successfully obtained. For simulated water samples (fluorine ion concentration is 6 mg/L),the fluoride removal efficiency reaches 44.6%,The fluoride removal capacity is 2.678 mg/g,which is higher than the test value of commercially available hydroxyapatite under the same test conditions (1.437 mg/g). According to thermodynamic [JP+2]parameters，adsorption of fluoride is a spontaneous process(ΔG0＜0) with reduced endothermic (ΔH0<0) and increased entropy (ΔS0＞0)．The kinetic simulation of fluoride absorption by hydroxyapatite is conformed to pseudo second-order kinetics. The prepared hydroxyapatite samples were made into particles and evaluated by continuous adsorption device. The fluoride concentration in the effluent remained below 1.0 mg/L for 9 days,which means the hydroxyapatite made in lab has a significant removal effect of fluoride.

0 引言

1 试验材料和方法

   1.1 试验材料

   1.2 分析测试仪器

   1.3 试验方法

2 结果与讨论

   2.1 单因素试验结果

   2.2 Box-Behnken试验结果与分析

   2.3 样品表征

   2.4 吸附热力学研究

   2.5 吸附动力学研究

   2.6 连续除氟试验验证

3 结论