不同合成方法的类水滑石对磷吸附特性研究

Study on Phosphorus Adsorption Properties by Layered Double Hydroxides with Different Preparation Methods

不同合成方法制备的类水滑石其结晶度、比表面积和孔容孔径存在差异,进而影响其吸附性能。该文采用水热法和共沉淀法制备了镁铝类水滑石(LDH-H和LDH-C),研究了初始pH、吸附时间、初始浓度和共存离子等对吸附磷酸根的影响,拟合了吸附动力学和吸附等温模型。结果表明:LDH-H在pH为3~6时性能更为稳定;LDH-H和LDH-C对磷酸根的吸附更符合拟二级动力学方程和Langmuir吸附等温模型,属于单层化学吸附;LDH-H的吸附速率是LDH-C的7.2倍,两者对应的最大吸附容量分别为41.003 mg/g和22.179 mg/g;低浓度的共存离子(Cl^(-)、NO_(3)^(-)、CO_(3)^(2-)和SO_(4)^(2-))对LDH-H和LDH-C吸附磷酸根的影响较弱。结合X射线衍射、傅里叶变换红外能谱对吸附前后的材料表征结果,LDH-H吸附性能优于LDH-C的原因在于其层间离子交换作用更强。该研究可为缓解水体的富营养化和开发高效除磷吸附剂提供技术支持。

Magnesium-aluminum layered double hydroxides(LDH)were prepared by hydrothermal(LDH-H)and co-pre⁃cipitation(LDH-C)methods to study the effect of LDH’s preparation method on its adsorption properties.The effects of initial pH,adsorption time,initial concentration,and co-existing ions on the adsorption of phosphate ions(PO43-)were investi⁃gated.The pH experiments showed that the adsorption performance of LDH-H was more stable at pH 3~6.The adsorption behaviors of PO43-on LDH-H and LDH-C were more fitted to the pseudo-second-order and Langmuir model,indicating a monolayer chemisorption process.Alternatively,the fitted adsorption rate constant(k2)of PO43-adsorption on LDH-H was 7.2 times higher than that on LDH-C,and the corresponding maximal adsorption capacity of LDH-H and LDH-C were 41.003 mg/g and 22.179 mg/g,respectively.Additionally,the PO43-adsorption by LDH-H and LDH-C was slightly affected by low concentrations of coexisting ions(Cl^(-),NO_(3)^(-),CO_(3)^(2-),SO_(4)^(2-)).X-ray diffraction and Fourier transform infrared spectrosco⁃py results implied that the superior adsorption performance of LDH-H was attributed to the stronger interlayer ion ex⁃change.This study could provide technical support for mitigating the eutrophication of water and developing efficient adsor⁃bents for phosphorus removal.