原位合成羟基磷灰石/壳聚糖复合吸附剂及除氟特性研究

利用原位共沉淀法合成了羟基磷灰石/壳聚糖复合吸附剂,通过扫描电镜、X射线粉末衍射、红外光谱和N2吸附-脱附曲线,研究复合前后羟基磷灰石的理化特征变化。实验结果表明与壳聚糖复合后羟基磷灰石的晶型并没有改变,只是结晶度有所降低,且复合后表面形成了不规则的凹凸结构,表面粗糙度增加。比表面积从106.75m2/g增加到127.58m2/g。复合吸附剂孔径大部分集中在10~50nm,属于介孔结构。利用Langmuir和Freundlich吸附等温方程对实验数据进行了拟合,对比相关系数R2值,Langmuir模型能更好地描述该吸附过程。复合吸附剂对氟离子的吸附符合拟二级反应动力学方程。计算了吸附热力学和动力学参数值,探讨了复合吸附剂对氟离子的吸附机理。ΔG0<0、ΔH0>0和ΔS0>0,说明复合吸附剂对氟离子的吸附是自发的、吸热的熵增过程,温度升高有利于吸附。吸附活化能(Ea)=15.03kJ·mol-1,迁移能(E)=7.639kJ·mol-1,说明该吸附过程以物理吸附为主。

In situ Fabrication of Hydroxyapatite/Chitosan Composite Adsorbent and Its Property for Defluorination

Hydroxyapatite/chitosan(HAP/CS) composite adsorbent was prepared by the in-situ co-precipitation method. The physical and chemical characteristics of adsorbents with and without CS were characterized via SEM, XRD, IR, and N2 adsorption-desorption isotherms. The results showed that crystal form of HAP has no change after composition, but the crystallinity was decreased. Moreover, the as-prepared composite has an irregular concave-convex structure with increased surface roughness. The specific surface areas also increased from 106.75 m2/g to 127.58 m2/g, and the pore size of composite adsorbent was 10~50 nm, which belongs to mesoporous. Both models, including the Langmuir and the Freundlich, could predict the experimental data conducted. However, the Langmuir model had a better correlation coefficient than the Freundlich model. The kinetic adsorption data showed that the adsorption process follows the pseudo-second-order kinetic. The thermodynamic and kinetics parameters were obtained. ΔG0<0、ΔH0>0 and ΔS0>0 indicated that the adsorption was a spontaneous and endothermic process with increased entropy, and a higher temperature would benefit the adsorption. The adsorption′s activation energy(Ea)=15.03 kJ·mol-1 and migration energy(E)=7.639 kJ/mol indicated that the adsorption was mainly physical.