Study On Hydrophilic Modification Of Polymer Membrane And Its Application In Oil-Water Separation

Membrane separation was a low cost,energy-efficient solution to separate oil–water mixtures.However,there were still many constraints and limitations involved in this process.Membrane fouling was an important factor that restricts its widespread application.In recent years,development of superhydrophilic and underwater superoleophobic membranes had become a research hotspot in the eld of membrane separation.Therefore,we prepared novel anti-fouling membranes by mussel-inspired chemistry.While improving the hydrophilicity of the polymer membrane,the modified membranes also had excellent resistance to oil.Here,polydopamine served as the intermediary layer,the organic-inorganic composite membrane（iPP@PDA@GO）was parepared by surface modification technology.Graphene oxide（GO）was anchored by polydopamine（PDA）on the surface of iPP membrane.The water contact angle of the iPP@PDA@GOmembrane was 0°,and the underwater oil contact angle was 152°.The modified membrane had excellent superhydrophilic and underwater superoleophobic property compared with the pristine membrane.In addition,when tested for the treatment of three different oil in water emulsions,the modified membrane exhibited wonderful surfactant-stabilized oil-water emulsions separation performance,including high oil-water permeation(188Lm^-2h^-1,0.1MPa)and superior oil rejection（>99%）.Furthermore,it could be seen from the SEM images there was no obvious oil stuck on the internal surface and inner pore of iPP@PDA@GO membrane,and the mechanical property of the membrane still maintained in great condition after several cycling test,indicating that the membrane had excellent antifouling performance and reusability.A novel polyvinylidene-fluoride（PVDF）membrane was prepared via a high-efficient deposition of polydopamine（PDA）coating oxidized by sodium persulfate（SP）.In contrast to the traditional PDA coating on membrane autoxidized by O₂,The modified membrane had excellent superhydrophilic and underwater superoleophobic property.The modified membrane also exhibited excellent chemical stability in harsh p H environments for practical applications.The as-prepared membranes could be applied in varieties of oil-in-water emulsions separation with ultrahigh permeate flux(above 1232Lm^-2h^-1)under ultralow operating pressure（only 0.04MPa）and excellent oil rejection（>99%）.After five cycles of oil-water separation tests,the flux recovery rate of PVDF@PDA@SP membrane was greater than 90%,indicating that the modified membrane has excellent recycling performance.In summary,these findings suggested that the modification has a great potential for the highly efficient oil-water emulsions separation and practical wastewater treatment applications.