Bio-inspired Preparation Of Separation Materials And Application For Dye Wastewater Purification

With the aggravating water pollution and shortage,methods and materials which can efficently purify the polluted water have arisen great attention.Among water purification methods,adsorption and membrane separation technologies have unique advantages for their less energy consumption and high separation effiency.Therefore,study and development of efficient adsorbents and membrane materials can solve the problem of water shortage.In this study,we firstly utilized the copolymerization reation between low-cost DOPA-derived gallic acid(GA)and polyethyleneimine,a cationic polyelectrolyte,to fabriate a magnetic adsorbent Fe3O4@GA/PEI and explore the application in water purification.The adsorbent is consist of the mangentic Fe3O4 core and outer GA/PEI adsorption layer.Transmission electron microscope(TEM),fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),Zeta potential and thermal gravimetric analysis(TGA)were utilized to characteristic the physical and chemical structures of Fe3O4@GA/PEI.Besides,the adsorption capacities of the preparaed Fe3O4@GA/PEI to various dyes were measured.The results have illustrated that the fabricated Fe3O4@GA/PEI shows the optimal water purification ability when reaction time is 9 h and the mass ratio between PEI and GA is 3:2.The highest adsorption capacities of Fe3O4@GA/PEI to anionic dyes methyl blue(MB)and rose Bengal(RB)are 243.5 mg·g-1 and 190.2 mg·g-1 respectively.However,the poor adsorption capacity to cationic dyes refines its application in dye wastewater purification.Besides,inspired by two dimensional stacked-layer structure of nacre,the nacre-like ultra-thin RGO&PEI composite nanofiltration membrane was prepared by crosslinking reaction between PEI and graphene oxide(GO)nanosheets.The assembly process of RGO&PEI membrane was actuated by pressure and followed by thermal reduction.The physical and chemical structures of RGO&PEI was characterized by SEM,Zeta potential,water contact angle analysis,XPS.Furthermore,the structure and property variations of different RGO&PEI membranes manufactured by various molecular weight of PEI,PEI concentration and GO concentration were investigated in this study.The nanofiltration test revealed that when the molecular weight of PEI is 1800 g mol-1,GO concentration is 2.5 mg L-1 and PEI is 2.5 mg L-1,the fabriated RGO&PEI composite nanofiltration membrane possess 95.8 L m-2 h-1 bar-1 pure water permeance and as high as 99.9% rejection to both of cationic dye Victoria blue B(VB)and anionic dye Methyl Blue(MB),together with superior water stability and acid-or alkali-resistant ability.Thus,we believe that the prepared RGO&PEI composite nonofiltration membrane can be applied in heavily polluted water for long time.