The Preparation Of Photothermal Amphiphobic Membrane And Its Anti-fouling Performance In Membrane Distillation

Recently,membrane distillation has brought significant attention regarding its feasibility of treating high salinity water that reverse osmosis cannot deal with.However,membrane fouling and membrane wetting would unavoidably occur during membrane distillation process.Changing the properties of membranes are the most crucial solution to address membrane fouling and membrane wetting.Fortunately,surface modification can endow membrane surface with new characteristics without destroying the bulk of membrane.In this work,commercial poly-vinylidene fluoride(PVDF)is used as substrate,hydrophilic polydopamine(PDA)is utilized to functionalize the pristine PVDF,and then nanosilver particles grew on the membrane surface by in situ method,endowing the membrane photothermal effect.Finally,the membrane was fluoridized by 1H,1H,2H,2H-perfluorodecanethiol.Consequently,a photothermal amphiphobic membrane with special structure and controllable wettability by surface design without influencing the membrane pore structure,pore size,porosity and thickness.The effect of operational conditions on membrane structure and chemical properties,including p H,the time of PDA deposition,the concentration of Ag~+,were studied in detail.Furthermore,the chemical and thermal stability of the amphiphobic membrane were investigated as well as its desalination effect and comprehensive anti-fouling performance in direct contact membrane distillation(DCMD).It is revealed that the water and oil contact angle of the amphiphobic membrane modified under optimal condition can achieve 167.6+0.27°and 136.9+0.4°,respectively,while the water sliding angle is only approximately 3°,which demonstrates prominent hydrophobicity,oleophobicity and self-cleaning property.In the long-term direct contact membrane distillation experiments The membrane flux of amphiphobic membrane can approximately stay constant at 28 kg/m~2h,the conductivity of permeate water is always lower than 8μS/cm,and the rejection can reach 99.9%..Additionally,under the radiation of ultraviolet light at 365 nm,the pure water flux of the amphiphobic membrane can approximately increase to 3.35 times as the pristine PVDF.Interestingly,its membrane flux can achieve as 3 times as the pristine PVDF even when dealing with simulated sea water and the conductivity of permeate water constantly stays low.To sum up,the photothermal amphiphobic membrane possesses high flux and prominent comprehensive antifouling performance,which shows promising potentials for application in the field of membrane distillation.