Preparation Of Polyethylene-imine Functionalized Composites And Their Adsorption Properties For Dyes

Congo red is a direct azo anionic dye with good chemical stability,water solubility and photothermal stability.The Congo red dissolved in water is difficult to be biodegraded.At present,various techniques have been used to remove Congo red dye from water,such as membrane separation,advanced oxidation and adsorption.The adsorption method is widely used for its high efficiency,low cost and simple operation.At present,most adsorbent materials have many problems such as complex preparation steps,high preparation cost,small adsorbent particles and difficult recovery.In this paper adhere to the concept of green chemistry,through simple synthesis methods to prepare low cost,simple synthesis process,can be easily enriched and recycled composite adsorption materials.Polyethylene imine（PEI）is a cationic polymer,which contains a large number of amino groups in its molecular structure and has strong adsorption capacity for anionic pollutants.In this paper,PEI was selected as the functional material of adsorption function,and polyethylene imine（PEI）was anchored on different substrate materials.Based on molecular diffusion adsorption and electrostatic adsorption theory,congo red was used as the target substrate for adsorption separation.The research contents are as follows:（1）Using 3-isocyanate propyl triethoxysilane（IPTS）to modify the halloysite nanotubes（HNTs）,a highly active isocyanate group was introduced on the surface of HNTs.The amino group in polyethyleneimine（PEI）reacted with the isocyanate group,and PEI was grafted onto the halloysite nanotubes to prepare HNTs@IPTS-PEI nanocomposite adsorbent.The maximum adsorption capacity of HNT@IPTS-PEI to congo red is 181.12 mg/g under the optimum experimental conditions.The experimental data fit well with pseudo-second-order kinetic model and Langmuir isothermal adsorption model,indicating that the adsorbent surface is uniform and the adsorption process is similar to monolayer chemisorption.The study of adsorption thermodynamics shows that high temperature is beneficial to the adsorption process.（2）In view of the problems of powder adsorption materials in chapter 1,particle size is too small and it is not easy to separate and recycle.In this chapter,PEI was anchored on the surface of（SA/GO）gel microspheres by chemical cross-linking method to prepare millimeter bead aerogel microspheres adsorbent（SA/GO）@PEI.The preparation method is simple,the microspheres are stable and can be separated from the solution only by simple filtration.The results showed that the maximum adsorption capacity of（SA/GO）@PEI was 128.65 mg/g at 303.15 K.The experimental data fitted well with the pseudo-second-order kinetic model,and the adsorption process was mainly controlled by chemical adsorption mechanism.The number of adsorption isotherms can be simulated by Langmuir isotherm model.The study of adsorption thermodynamics shows that high temperature is beneficial to the adsorption process.（3）In order to shorten the adsorption equilibrium time and achieve rapid separation of adsorbent in solution.In this chapter,magnetic nanomaterial Fe₃O₄ and adsorption functional material PEI are combined to prepare magnetic Fe₃O₄@PDA-PEI core-shell material by one-pot method.The adsorption capacity of Fe₃O₄@PDA-PEI to congo red was 139.08 mg/g at 303.15 K.The adsorption isotherm data fit well with Langmuir isotherm model,indicating that the adsorbent surface is uniform.The experimental data fit well with the pseudo-second-order kinetic model,and the adsorption process is mainly controlled by chemical adsorption mechanism.The preparation method of the composite material is simple,it can be recovered by simple magnetic separation,and the adsorption equilibrium can be achieved within 60min.