Preparation And Adsorption Properties Of Three-dimensional Layered Double Hydroxide/graphene Nanocomposites

With the rapid development of global industry,the output of industrial wastewater is increasing day by day,and the problem of water pollution is becoming more and more prominent.Adsorption method is recognized as an efficient and cheap water treatment technology,but most of the existing adsorbents have defects such as adsorption capacity,recovery and utilization difficulties,so how to prepare efficient and easy to recover the adsorbents has become a problem.2D graphene has made great progress in treating sewage by adsorption,but it is still difficult to recycle.Recent studies have found that the preparation of two-dimensional graphene materials into three-dimensional graphene materials can not only enhance their adsorption properties,but also effectively solve the problem of difficult recycling.Therefore,in this paper,one-step in-situ hydrothermal synthesis of three-dimensional Mg-Al layered double hydroxide(LDH)/graphene nanocomposites and three-dimensional Mg-Fe LDH/graphene nanocomposites were used to systematically characterize the prepared materials by XRD,SEM,FTIR,Raman,XPS and BET characterization techniques.The adsorption properties of the two composites for methylene blue(MB)and ciprofloxacin(CIP)were investigated.The specific research results are as follows:1.Three-dimensional Mg-ferrotalcite/graphene nanocomposites were successfully prepared by one-step in-situ hydrothermal method,and their adsorption properties for MB and CIP were investigated.The adsorption kinetics of MB was consistent with the second-order kinetic model and the thermodynamic performance was consistent with the Freunlich adsorption isotherm model.The optimal adsorption condition was 318 K,and the adsorption capacity was 490.96 mg/g at the adsorption equilibrium.The adsorption process is endothermic and high temperature is beneficial to adsorption.After 5 times of adsorption-desorption experiments,the adsorption capacity of MB is 77.14% of that of the first time,which still maintains a high adsorption performance.The CIP adsorption kinetics was consistent with the second-order kinetic model and the thermodynamic performance was consistent with the Freunlich adsorption isotherm model.The optimal adsorption condition was 318 K,and the adsorption capacity was 182.90 mg/g at the adsorption equilibrium.The adsorption process is endothermic and high temperature is beneficial to adsorption.After 5 times of adsorption-desorption experiments,the adsorption amount of CIP is 53.79% of the first time,which still maintains a high adsorption performance.2.Three-dimensional Mg-Al hydrotalcite/graphene nanocomposites were successfully prepared by loading Mg-Al hydrotalcite on 3D graphene materials;The adsorption kinetics of MB was consistent with the second-order kinetic model and the thermodynamic performance was consistent with the Langmuir adsorption isothermal model.The optimal adsorption condition was 318 K,and the adsorption capacity was439.71 mg/g at the adsorption equilibrium.The adsorption process is endothermic and high temperature is beneficial to adsorption.After 5 times of adsorption-desorption experiments,the adsorption amount of MB is 79.99% of the first time,which still maintains a high adsorption performance.The CIP adsorption kinetics was consistent with the second-order kinetic model and the thermodynamic performance was consistent with the Freunlich adsorption isotherm model.The optimal adsorption condition is 288 K,and the adsorption capacity is 606 mg/g at adsorption equilibrium.The adsorption process belongs to exothermic process,low temperature is beneficial to adsorption.After 5 times of adsorption-desorption experiments,the adsorption capacity of CIP is 85.34% of the first time,which still maintains a high adsorption performance.