Preparation And Application Of Functional Graphene Oxide Composite Membrane

Pb(II)is a kind of non-degradable toxic heavy metal,which will accumulate in human body when discharged into the environment.It is harmful to human body.Therefore,an effective adsorbent is urgently needed to treat lead ion(II)in water environment.Graphene oxide(GO)has a large specific surface area and contains a variety of oxygen-containing functional groups.Through effective modification,it can achieve efficient adsorption of lead ion(II),and the membrane material composed of GO has a excellent separation performance toward heavy metal ions.In this paper,functional graphene oxide was prepared by post grafting method,and then GO/PVDF composite membrane was obtained by vacuum filtration method.Firstly,amino-functionalized graphene oxide(N-GO)was prepared by grafting diethylenetriaminopropyltrimethoxysilane(NQ-62)onto GO surface.Correspodingly,N-GO/PVDF composite membrane was obtained by vacuum filtration method.Thiophene functionalized graphene oxide(A-GO)and A-GO/PVDF composite membrane were prepared by grafting 2-acetylthiophene onto N-GO surface by Schiff base reaction.Specially,thiophene functionalized graphene oxide(F-GO)could be prepared by one-step synthesis.In this preparation process,Schiff base intermediate was firstly synthesized through the reaction between 2-acetylthiophene and NQ-62,and then the Schiff base intermediate was introduced onto GO surface to obtain F-GO,finally the F-GO/PVDF composite membranes could be prepared.The adsorbents were characterized by TEM,SEM,EDX,FT-IR,TGA,Raman spectrum and XRD.Effects of p H value,adsorption time,adsorption temperature and initial concentration on the adsorption performance were investigated.As a result,the optimum adsorption conditions were obtained.The adsorption thermodynamics,kinetics and isotherm were analyzed,and the corresponding mathematical model was established.The adsorption mechanism of different functionalized graphene oxide for Pb(II)was determined by the combination of adsorption behavior and characterization methods.SEM,TEM,Raman and XRD showed that the distance between the functionalized go layers increased and the layers peeled off.The analyses of FT-IR and XPS showed that thiophene groups were successfully grafted onto the GO surface.The adsorption capacity of N-GO,A-GO and F-GO toward Pb(II)were 347.2mg/g、408.2mg/g and 787.4mg/g,respectively.The results of adsorption kinetics showed that the adsorption of Pb(II)by N-GO,A-GO and F-GO could be well described by the pseudo-second-order kinetic model,mainly chemical adsorption and membrane diffusion.Langmuir model can well describe the isothermal process of adsorption,that is,monolayer adsorption.The adsorption process is spontaneous,endothermic and entropy increasing.In addition,in the coexistence system of Cu(II),Zn(II)and Ni(II),the adsorbent has good selectivity for Pb(II).The separation performance of N-GO/PVDF,A-GO/PVDF and F-GO/PVDF membranes for Pb(II)in aqueous solution was studied.The effects of loading amount of functionalized graphene oxide on PVDF,operating temperature,initial p H value and initial concentration of Pb(II)on the separation of Pb(II)were systematically studied.The results showed that the removal rates of Pb(II)by N-GO/PVDF,A-GO/PVDF and F-GO/PVDF membranes at 60 °C were 85%,94.1% and 97.2%,respectively.The results show that F-GO has high adsorption capacity,good reusability and selectivity,and its corresponding F-GO/PVDF membrane has good separation performance,which has potential application in the adsorption of Pb(II)from aqueous solution.