Design And Adsorption Properties Of Functionalized Chitosan Electrospun Nanofiber Membranes

Water pollution has become a serious problem today.Heavy metals and organic dyes in sewage are difficult to be degraded,causing great harm to the environment and human health.Therefore,it is of great significance to develop a kind of green non-toxic adsorbent with high adsorption performance.In this paper,CS/PEO composite nanofiber membranes were prepared by electrospinning with chitosan(CS)as raw material and polyoxyethylene(PEO)as auxiliary agent.Then,the polyglycidyl methacrylate(PGMA)and polyethyleneimine(PEI)molecular brushes are sequentially grafted onto the CS nanofibers by a ring-opening reaction between the amino group and the epoxy group to obtain the CS-PGMA-PEI nanofibers.Finally,the morphology,chemical composition and surface functional groups of the nanofiber membranes were characterized by SEM,TG,ATR-FTIR,XRD,DSC and XPS,which verified that the PEI molecules were grafted into the CS nanofiber membranes.The ability of adsorption Cr(Ⅵ),Cu(Ⅱ)and Co(Ⅱ)of the CS-PGMA-PEI nanofiber membranes were investigated.The effects of initial pH,adsorption time and initial concentration on the adsorption effect were investigated,and the adsorption behavior,adsorption mechanism and recycling performance of Cr(Ⅵ),Cu(Ⅱ)and Co(Ⅱ)were studied.The results showed that the solution could reach the adsorption equilibrium rapidly within 60 min,and the pseudo-second-order kinetic model could be better fitted to the experimental data.The adsorption isotherm could be described by the Langmuir model of the monolayer theory.The maximum adsorption capacities calculated by Langmuir model were 138.96,69.27 and 68.31 mg/g for Cr(Ⅵ),Cu(Ⅱ)and Co(Ⅱ),respectively.The adsorption-desorption cycle experiments showd that the membrane samples had good recycling properties.The ability of adsorption Congo red(CR)dye of the CS-PGMA-PEI nanofiber membranes were investigated.The effects of initial pH value,adsorption time,temperature and initial concentration on the adsorption capacity were investigated,and the adsorption behavior,adsorption mechanism and recycling performance of CR dye were studied.The results showed that the maximum adsorbing capacity reached 657.47 mg/g with initial pH 8,contact time 4 h,initial concentration 800 mg/L and temperature 25℃.The pseudo-second-order kinetic model could be better fitted to the experimental data,and the adsorption isotherm can be described by the Langmuir model.Thermodynamic analysis showed that AG0<0,ΔH0>0 andΔS0>0 at temperatures of 288,298,308,318 and 328 K,indicating that the adsorption process of CR on membrane samples was a spontaneous and entropy increasing endothermic reaction.The adsorption-desorption cycle experiments were carried out on the membrane samples,and the membrane samples showed good recycling performance.