Synthesis Of Inorganic Polyaluminum Cationic Framework Materials And Study On Adsorption Performance Of F^- And Cr（Ⅵ）

An important factor leading to water pollution is caused by anionic pollutants,such as F^-and Cr（Ⅵ）.Due to the easy migration and diffusion of anionic pollutants in nature,the pollution of water bodies is often more serious.Cationic framework materials are considered to be one of the effective materials for removing anionic pollutants,and it is imminent to find cationic framework materials with excellent removal performance.Most of the inorganic framework materials existing in nature are neutral or negatively charged,and only a few are cationic framework materials,such as layered double hydroxides（LDHs）and layered rare earth hydroxides（LRHs）.The number and structure of cationic framework materials are very limited.Therefore,it is of great significance to develop novel,low-cost,high-efficiency,environment-friendly,inorganic cationic framework compounds with strong ion selectivity and excellent adsorption performance.Determining the microstructure of a new material is usually the most difficult step in the study of new materials.In recent years,the development of three-dimensional electron diffraction（3D-ED）techniques using transmission electron microscopy has overcome the barriers of nanoscale and submicron scale crystal structure analysis.It breaks the barrier that single crystal structure analysis can only be determined by X-ray diffraction of large crystals（>50μm）,and the crystal structure analysis only requires data collection and structure analysis of nano-single crystal samples.In this paper,for the first time,the Themis Z aberration-corrected transmission electron microscope was used to successfully collect microcrystalline three-dimensional electron diffraction（3D-ED）data under ultra-low temperature conditions through continuous tilt data collection（c RED）,and used REDp,XDS and shelx software nalyze the crystal structure.In this paper,an inorganic polyaluminum cationic framework material was successfully synthesized,and a purified crystalline single phase of the compound was obtained by controlled hydrolysis,but it was still unable to obtain a single crystal large enough for X-ray single crystal diffraction（SXRD）analysis.At the same time,due to the small number of powder diffraction peaks,it is difficult to determine its crystal structure using PXRD data.In this paper,for the first time,the Themis Z aberration-corrected transmission electron microscope was used to successfully collect three-dimensional electron diffraction（3D-ED）data under ultra-low temperature conditions through continuous tilt data collection（c RED）.The crystal structure of this new material uses REDp,XDS and shelx software analysis to obtain and the results show that it is a new type of inorganic cationic two-dimensional layered structure,with the constant anion Cl^-in the interlayer.Due to its unique spatial structure,the adsorption performance for the removal of F-and Cr（Ⅵ）was further investigated.Combined with XRD,XPS,SEM,FT-IR,EDS and other characterizations,the adsorption mechanism was explored,and the following conclusions were drawn:（1）Two crystalline inorganic polyaluminum cationic adsorbents were prepared by controlled hydrolysis,named:Infinite-Flat-Al₈and named:Infinite-Al₁₀.（2）The research on the adsorption performance of F^-shows that Infinite-Flat-Al₈has excellent adsorption performance:under the condition of low dosage（1.0g/L）,it has a wide p H value response range（3-11）,high removal efficiency（>95%）,ultra-fast adsorption speed（<1min to reach adsorption equilibrium）;adsorption capacity（207mg/g）is higher than other adsorbents of the same type.（3）Research on the adsorption performance of Infinite-Flat-Al₈and Infinite-Al₁₀on Cr（Ⅵ）,the research results show that the dosage is low（<1.0g/L）and has a wide p H response range（3-10）.And the removal efficiency is high,showing a fast adsorption rate（>99%）;the adsorption kinetics are in line with the pseudo-second-order kinetic model.The adsorption isotherms are in accordance with the Freundlich isotherm equation.However,the adsorption selectivity of Cr（Ⅵ）by Infinite-Flat-Al₈and Infinite-Al₁₀is poor,which will be interfered by high-valent anions,which will affect the removal efficiency,which needs to be further optimized.