Preparation And Application Of Super-hydrophilic/underwater Super-oleophobic Membrane

There is still an urgent need for the development novel green materials with high separation capacity,aiming to resolve industrial oily wastewater and oil-spill pollution.Based on the relationship of wettability of materials and surface structure,we chose porous polypropylene microfiltration membrane(PPMM,mean pore size 0.2μm,porosity 75%)as the support and report the fabrication of the novel superhydrophilic and underwater superoleophobic materials that are polydopamine(PDA)and polyethyleneimine(PEI)decorated PPMMs using a facile approach of depositing hydrophilic polymer on the surface.Meanwhile,we designed and fabricated a GO coated PDA/PEI/PPMM structure with an optimized hierarchical surface roughness for antifouling oil/water separation.Moreover,the optimal fabrication conditions,wettability,oil-water separation and antifouling performance of modified membrane are systematically studied.(1)The PDA/PEI-decorated membranes show more excellent wettability afer a shorter deposition time than PDA-decorated.Furthermore,The optimal conditions for the fabrication of PDA/PEI/PPMM are that the deposition time is 4h,the molecular weight of PEI is 600,and the ratio of DA to PEI is 1:1.Interestingly,our PDA/PEI-decorated membranes show superhydrophilicity(WCA is 0 °)and underwater superoleophobicity(an underwater oil contact angle of 164.38°),compared with the hydrophobic nascent PPMM.(WCA is 134.43°)(2)PDA/PEI/PPMM modifed by 50%GO,“water-locking” GO coatings with the optimized hierarchical surface roughness,provided by the inherent roughness of the porous PDA/PEI/PPMM supports and the corrugation of the GO coatings,minimizes underwater oil adhesion on the membrane surface.(3)We have tested the membrane to separate a series of surfactant-stabilized oil-in-water emulsions with PDA/PEI/PPMM and GO/PDA/PEI/PPMM.A high separation efficiency(>99%)and a higher separation efficiency(>99.5%)were achieved by using PDA/PEI/PPMM and GO/PDA/PEI/PPMM respectively.Particularly,GO/PDA/PEI/PPMM generates a group of low-oil-adhesion and has a excellent antifouling and easy-to-recover capability.