Preparation And Surface Properties Of GO/g-C₃N₄ Visible Light Photocatalytic Separation Membrane

In the field of membrane separation,poly?vinylidene fluoride??PVDF?has been widely studied and applied due to its simple preparation process,good toughness,high mechanical strength and high plasticity.However,due to the strong hydrophobicity of PVDF membrane,it is easy to cause serious membrane fouling in practical applications,resulting in the increase of operation cost and membrane life of membrane modules,which further restricts the popularization of membrane technology.The photocatalytic separation membrane was prepared by coupling the photocatalytic technology with membrane separation technology,which can effectively solve the problem of membrane fouling.Photocatalytic degradation of organic pollutants can effectively alleviate membrane fouling,but there are still some problems in the photocatalytic separation membrane,such as the lack of photocatalytic activity and the weak photocatalytic efficiency and narrow spectrum response range,which can not make use of visible light but only use ultraviolet light and so on.This topic is based on the graphene oxide?GO?and graphite phase nitride carbon?g-C₃N₄?was used as modifiers.To take the combined modification method with in situ dispersion polymerization and ultrafiltration pumping the surface modification on polyvinylidene fluoroethylene plate ultrafiltration membrane?for short original membrane?was conducted.The new nano composite modified membrane with visible-light photoresponse was obtained?GO/g-C₃N₄ modified membrane?.The optimal preparation conditions of the GO/g-C₃N₄ modified membrane and its surface properties as below were investigated:retention performance?hydrophilicity?anti-fouling characteristics and the visible-light photocatalytic activity on rhodamine B?RhB?.The results were shown that:The optimum preparation conditions for the modified GO/g-C₃N₄ film are obtained:1.The optimum preparation conditions for the modified GO/g-C₃N₄ film are obtained:g-C₃N₄ dosage 10mg,The ratio of g-C₃N₄ to GO 80,the concentration of aniline0.5wt%,soak time of aniline 4 hours,the APS concentration 0.8g/L,ammonium persulfate soak time 3 hours.2.The hydrophilicity of GO/g-C₃N₄ modified membrane was improved significantly,the surface contact angle decreased from 78.2°±1.1°to 35.1°±1.4°.There are clear absorption peaks of-OH,C-O,C=O,-NH,-NH₂ and other hydrophilic groups on the surface of the modified membrane,he mass ratio of element O to C was raised to 0.401from 0.052.3.The GO/g-C₃N₄/polyaniline composite modified layer was firmly attached to the surface of GO/g-C3N4 modified membrane.The specific stretching vibration peak of polyaniline,such as N=Q=N and N-B-N,was obvious,and the tensile strength and the tensile modulus of elasticity increased significantly..4.The improvement of the surface resistance of GO/g-C₃N₄ modified membrane is obviously improved,The flux attenuation rate decreased from 70.6%before the modification to 37.9%,and the membrane flux recovery rate increased from 39.5%of the original film to 81.5%after the hydraulic flushing.5.GO/g-C₃N₄ modified membrane has demonstrated strong visible-light photocatalytic ability.The maximum absorption band of GO/g-C₃N₄ modified membrane is 495nm,The band gap?Eg?value of the surface modified functional layer is 2.5eV?The value of the pure g-C₃N₄ corresponds to 2.7 eV?.Under the condition of visible light,the modified membrane of GO/g-C₃N₄ was used to the treatment of Rhodamine B?RhB?for 5hrs continuously,the removal rate of visible-light photocatalytic degradation can reach 81.2%,while that of the original membrane was only 42.2%.6.Under the dark condition,the concentration of RhB and CR solution decreased by the adsorption of GO/g-C₃N₄ modified membrane and the original film.Compared with the original film,the anti pollution ability of GO/g-C₃N₄ modified membrane to RhB and CR solution was significant.The adsorption removal rate of the modified membrane on the anion dye CR was higher than that of the cationic dye RhB solution.7.Under the light condition,the RhB and CR solution of GO/g-C₃N₄ modified membrane not only has adsorption,but also has strong photocatalytic degradation effect.The degradation rate of GO/g-C₃N₄ modified membrane to CR solution is significantly higher than that of RhB solution.Under the condition of visible light driving,Luo Danming B?RhB?5h was treated continuously.The removal rate of photocatalytic degradation could reach 81.2%,while the removal rate of the original film to RhB was only 42.2%.For the treatment of Congo red?CR?5h,the removal rate of photocatalytic degradation can reach92%,while the removal rate of the original film to CR is only 45.6%.8.Under the light condition,the composite modified layer on the surface of GO/g-C₃N₄ modified membrane has visible light photocatalysis,which can effectively degrade the contaminants on the surface.Under the same illumination time,continuous illumination has better catalytic effect than multiple intermittent illumination.Under a long time of illumination,the pore structure of GO/g-C₃N₄ modified membrane did not change,and its physical properties remained stable.