Preparation Of Superantifouling Membrane For Oil/Water Separation And Study Of Separation Performance

Recently,more and more oily wastewaters are being produced by massive discharge of industrial sewage and frequent spillage of oil.The mass discharge of oily wastewater will cause serious damage to environment and ecology.Therefore,effective separation and rational recovery of oily wastewater meet the double needs of economic development and environmental protection.Compared with traditional oil/water separation technology,membrane separation has the advantages of simple operation,high separation efficiency and energy saving,etc.However,it is difficult to effectively solve the membrane fouling problems.In addition,the mechanism for oil/water（liquid-liquid）separation via membrane is much less studied.Therefore,it is necessary to reveal the antifouling mechanism of superwetting oil/water separation membrane and to prepare superantifouling membrane to solve the membrane fouling problem during continuous oil/water separation.Firstly,a membrane with enhanced superhydrophilicity-underwater superoleophobicity was fabricated by constructing polydopamine（PDA）micro-/nano-spheres on a polyacrylonitrile（PAN）nanofibrous membrane.The obtained composite membrane showed excellent antifouling performance.Permeability of obtained nanofiber composite membrane was maintained as high as 11666±978 L·m^-2·h^-1·bar^-1 with separation efficiency of higher than 99.9% over a 2-h continuous filtration.This permeability was about 2.7 times of pristine PAN membrane(4260±430 L·m^-2·h^-1·bar^-1).Based on the excellent separation performance of the composite membrane,extrusion and cutting demulsification was proposed.Then,antifouling mechanism of the membrane was first theoretically elucidated based on hydration ability and adhesion free energy with recourse to thermal analysis and extended Derjaguin-Landau-Verwey-Overbeek（XDLVO）theory respectively.It was found that PDA micro-/nano-spheres mediated membrane showed strong hydration ability and weak adhesion towards toluene compared to pristine PAN membrane.However,analysis of the results showed that the membrane fouling cannot be fundamentally solved only by the common superwetting modification.Finally,we broke the traditional membrane separation way of oil/water separation and fabricated an superantifouling oil/water separation membrane.When the membrane was used to separate oil/water emulsions,while the water phase passed through the membrane continuously,the oil phase also passed in the form of large oil droplets after demulsification.The membrane fouling caused by the accumulation of oil on the membrane surface was solved.When the membrane was employed to separate toluene-in-water emulsion,the permeability of the membrane could reach to 1078±50 L·m^-2·h^-1·bar^-1 with separation efficiency of higher than 99%.After 2-h of separation,the permeability reduction rate of the membrane was very low（<4%）without separation efficiency reduction.In addition,when applied to separate higher viscosity of D5-in-water emulsion,the membrane also showed excellent separation and antifouling performance.Based on the excellent antifouling performance and separation efficiency of the membrane,simultaneous demulsification on the membrane surface and inside the membrane was proposed,the main influencing factors on the separation performance were also investigated.The study is beneficial for the scale-up application of oil/water separation membrane and provide a new perspective for the development of antifouling oil/water separation membrane.