The Preparation And Application Properties Of Sepiolite Loaded β-Cyclodextrin Adsorbent Were Studied Based On First Principles

Sepiolite has a large specific surface area and nanosized channels,which can be used to treat environmental problems such as water,air and soil pollution.However,the defects of low grade and high impurity content limit the practical application of sepiolite.β-cyclodextrin has a unique cavity structure,which can capture many molecules matching its size and polarity and effectively remove all kinds of pollutants in water.However,due to the solubility of its monomer,it loses a lot in the process of use and is not easy to separate and recycle.In this paper,based on the special structure of sepiolite and β-cyclodextrin,using γ-glycidyl ether oxypropyl trimethoxysilane(KH560)as crosslinking agent,β-cyclodextrin adsorbent supported by sepiolite was prepared successfully.Response surface method was used to optimize the preparation process of KACDS and test its adsorption properties for phenol(representative of organic pollutants)and Cr(Ⅵ)ions(representative of heavy metal pollutants).Finally,the properties of sepiolite surface after acidification and the adsorption behavior of β-cyclodextrin molecules on the acidified surface were studied by first principles.The main research results are as follows:(1)KACDS was successfully prepared as β-cyclodextrin composite loaded with pelolite.Using phenol as adsorbent,single factor and response surface method were used to optimize the preparation conditions of KACDS: the mass ratio ofβ-cyclodextrin derivatives to acidified sepiolite was 8:6,the modification time was16 h,the modification temperature was 35℃,the maximum adsorption capacity of phenol was 2.4899 mg/g.It was characterized by scanning electron microscopy(SEM),infrared spectroscopy(FTIR),specific surface area(BET)and thermal analysis.The results showed that β-cyclodextrin not only covered the sepiolite surface,but also formed chemical bonds with the sepiolite surface.Moreover,the adsorption capacity of KACDS for phenol was obviously better than that ofβ-cyclodextrin and natural sepiolite.(2)Appropriate amount of inorganic acid solution can purify and activate sepiolite.In the experiment,three kinds of acids,namely sulfuric acid,nitric acid and hydrochloric acid,were selected to acidize sepiolite.Through XRD analysis and comparison of adsorption properties of phenol,the optimum acidizing conditions of acidified sepiolite were determined as follows: concentration of hydrochloric acid is 1.2 mol/L,reflux temperature of condensation is 80℃,stirring time is 12 h,and the best adsorption effect of KACDS for phenol is 2.4801 mg/g.(3)To explore the influence of different experimental conditions on the adsorption of phenol solution and Cr(Ⅵ)solution by KACDS,it can be concluded that the adsorption effect is the best when the initial adsorption concentration of KACDS is 100 mg/L at 25℃ and the p H is 7 phenol solution is 100 min,and the removal rate can reach 95.03%.The initial adsorption concentration of 20 g/L KACDS was 80 mg/L,and the adsorption effect was the best when Cr(Ⅵ)solution with p H=7 was added for 100 min.The maximum removal rate was75.22%.The adsorption effect of KACDS on phenol and Cr(Ⅵ)was higher than that of acidized sepiolite and protosepiolite,and the removal rate of phenol by KACDS was better than that of Cr(Ⅵ).The kinetic experiments show that the adsorption of KACDS to phenol solution is more consistent with the second-order kinetic model.The recycle experiment of KACDS shows that KACDS has good regeneration performance and can be recycled.(4)Based on the first principles,substituting H for different number of Mg atoms on sepiolite(001)surface electronic structure properties,the replacement of a small number of Mg atoms by H will not affect the overall atomic configuration of sepiolite(001)surface,and make it easier to open the internal channels of sepiolite,thus increasing the surface conductivity of sepiolite and effectively improving the catalytic efficiency of sepiolite.The optical properties of sepiolite(001)have been studied.It is concluded that H substituting Mg atomic energy can improve the response ability of sepiolite(001)surface to the range of visible light and the refractive index and extinction coefficient of its atomic system,without affecting the surface light absorption range of sepiolite(001).Through molecular dynamics simulation,it is shown that a comprehensive multilayer solvation structure can be formed between sepiolite and all acid solutions,and the interaction between sepiolite and 1.2mol/L hydrochloric acid molecules is the strongest at80℃.(5)Based on the first principles,the mechanism of the interaction between KACD,a molecular derivative of β-cyclodextrin,and acid-modified sepiolite was explained from the microscopic point of view.The mechanism of the interaction between KACD,a molecular derivative of β-cyclodextrin,and acid-modified sepiolite(001)was formed by substituting H with Kacd,a derivative ofβ-cyclodextrin,to form a three-dimensional structure of-Si-O-Si.The atomic orbitals on the surface of sepiolite(001)are stable after adsorption of KACD molecules,and the interaction between Si and O atoms is enhanced,while the interaction between Mg atoms is weakened.