改性羟基磷灰石制备及除氟特性研究

Preparation and Absorption Property of Modified Hydroxyapatite for Fluoride Ion

为了提高羟基磷灰石(HAP)的除氟容量,利用羟基铝(Al-OH)改性HAP制备羟基铝-羟基磷灰石复合材料(Al-OH-HAP),通过红外光谱(FTIR)、扫描电镜(SEM)、X-射线粉末衍射(XRD)和N2吸附-脱附曲线等方法对样品进行表征分析,结合吸附热力学和动力学模型拟合,探讨Al-OH-HAP对水溶液氟离子的吸附特性。实验结果表明:Al-OH改性后Al3+和OH-进入HAP晶格中,且改性后HAP的衍射峰更尖锐,结晶度增大。Al-OH改性后HAP的比表面积分别从106. 75 m2/g增加到220. 45 m2/g,且大部分孔为介孔结构。吸附拟合模型表明Al-OH-HAP对氟离子的吸附更加遵循Langmuir模型,说明Al-OH-HAP对F-的吸附更趋近于单层吸附,吸附过程中化学吸附占主导地位。热力学参数吸附吉布斯自由能(ΔGo)小于0、焓变(ΔHo)和熵变(ΔSo)大于0,说明Al-OH-HAP对F-的吸附是一个自发吸热的熵增过程,Al-OH-HAP对F-的吸附更符合拟二级反应动力学过程。Al-OH-HAP可以成为一种有潜力的饮用水除氟剂。

Defluoridation adsorbent hydroxy-aluminium hydroxyapatite(Al-OH-HAP)was prepared by modification of HAP with hydroxy-aluminium to improve the defluoridation capacity.The properties and structure of Al-OH-HAP were characterized by FTIR,SEM,XRD and N 2 adsorption-desorption curve.The defluoridation properties of Al-OH-HAP were discussed.The results showed that the Al-OH was successfully exchanged into the HAP,and the diffraction peaks of Al-OH-HAP were sharper.The specific surface areas of HAP increased from 106.75 m 2/g to 220.45 m 2/g after modification of Al-OH,and most of pores belonged to mesoporous.The fitness of adsorption data by Langmuir model was superior to Freundlich model.The adsorptions of fluorid ion on Al-OH-HAP are belonging to monomolecular layer adsorption and chemical adsorption.According to thermodynamic parameters,adsorption of fluoride was a spontaneous reaction(ΔG o<0),endothermic(ΔH o >0)and entropy increasing(ΔS o >0)process.The kinetic simulation of fluoride absorption by Al-OH-HAP is conformed to pseudo second-order kinetics.The Al-OH-HAP adsorbent could be employed as a promising adsorbent for fluoride adsorption from drinking water.