Preparation And Properties Of Superhydrophilic-underwater Superoleophobic EVAL/F127 Blended Porous Membrane

Nowadays,global water resources are scarce,and the treatment and reuse of water resources is particularly important.Oily wastewater will be produced in the industrial field and life.Therefore,a method for treating oily wastewater is urgently needed.In recent years,the superhydrophilic-underwater superoleophobic porous membranes used for treating oily wastewater have been favored by a large number of scholars.Due to the excellent hydrophilicity and stability,the polyvinyl vinyl alcohol copolymer(EVAL)has become one of the choices for membrane materials.Pluronic F127 hydrophilic additive has attracted a lot of attention because of its good hydrophilicity and the role of the porogen.Based on these contents,the paper aims to solve the problems by preparing the super hydrophilic-underwater superoleophobic EVAL/F127 blend porous membrane by immersion precipitation.First of all,an EVAL/F127 blended porous membrane(F membrane)was prepared by immersion precipitation.As a control,a membrane without F127 was called EVAL porous membrane(E membrane).Pluronic F127 plays a dual role of hydrophilic agent and porogen,in which propylene oxide(PPO)segment can be firmly anchored on the membrane surface,and the ethylene oxide(PEO)segment plays a significant role of hydrophilic.Through the study of the additional content of Pluronic F127 and the composition of coagulation bath,it was found that when the addition amount of F127 is 10%(relative to EVAL)and the addition amount of DMSO in coagulation bath is 5%,the performance of F membrane was the best.At this time,the hydrophilicity of the membrane was greatly improved,the water flux could reach 452.23 L/(m~2·h),and the flux recovery rate(FRR,which is an important index for evaluating the anti-fouling performance of the membrane,the greater the recovery rate,the better its anti-fouling performance)is also increased 60%to 75%.Secondly,based on the F membrane,immersion precipitation assisted with micromolding(PSμM)EVAL/F127 blended porous membrane was prepared..The influence of the number of mesh and semi-gel time on the structure and properties of the membrane was investigated.When the number of sandpaper mesh was 500#and the separation time of semi-cured membrane away from template was 60 s,the structure and performance of the membrane was the best,and the membrane reached super hydrophilic-underwater super oleophobic(water contact angle spreads instantly,underwater oil contact angle is greater than 150°).At this time,the anti-fouling performance of the membrane was also improved.The rough surface of membrane produced greater repulsive force against the contamination.The repulsion between the pollutant and the membrane reduced the adhesion,so that the membrane could be recovered by backwashing.Finally,three types membrane(E membrane,F membrane and S membrane)were tested for oil-water emulsion in separation experiment(petroleum-in-water emulsion,soybean oil-in-water emulsion,and diesel-in-water emulsion).Through the investigation of chemical oxygen demand(COD)and cyclic stability,the permeation flux by S membrane filtration was greatly improved,in which COD in soybean oil decreased from the original1710 mg/L to less than 500 mg/L,and the oil removal rate was greater than 82.7%.F127blocked pollutants by combining with water molecules to form a hydrated layer.The"valley"structure in the microstructure was clean and the"ridge"structure collected pollutants.The synergy of the two made the S membrane more resistant to pollution than the flat membrane.After 20 cycles of oil-water emulsion,COD still met the national petrochemical industry emission standards.