| PVDF is one of the most commonly used organic membrane materials,which has received widespread attention in recent years by researchers and manufacturers.PVDF has good corrosion resistance,as well as strong resistance to ultraviolet radiation,chemical stability and mechanical strength,which is very important for the practical application of the separation membrane.However,PVDF membranes are poor in hydrophilicity,are easily contaminated during application,resulting in reduced membrane efficiency and increased operating costs.Hydrophilic modification of PVDF membranes is an effective way to solve the above problems.In this paper,nano AgCl/Poly(MMA-St)/PVDF blended ultrafiltration membranes with copolymer(Poly(MMA-St))of nano AgCl,methyl methacrylate(MMA)and styrene(St)co-doped were prepared by microemulsion and its polymerization technique.The morphology and structure of the ultrafiltration membrane were characterized and the performance of the ultrafiltration membrane was evaluated.The main research contents are as follows:1?Using AgNo3 and NaCl as precursors,sodium(2-ethyl)hexyl succinate(AOT)as surfactant,and a mixture of methyl methacrylate(MMA)and styrene(St)as oil phase medium,forming microemulsions comprising nano AgCl,and then obtain a composite comprising nano AgCl emulsion and Poly(MMA-St)copolymer by microemulsion polymerization.The effects of AgNo3,NaCl concentration(CAgNO3,CNacl),solubilized water(?)and polymerization time on nano AgCl/Poly(MMA-St)composite emulsion were investigated.And the optimal preparation conditions for the composite emulsion were determined as follows:?= 2?3,CAgNO3 = CNaCl = 0.1-0.5 mol·L-1,CAOT = 0.2 mol·L-1,and the microemulsion polymerization time was 5?7 h.2?Nano AgCl/Poly(MMA-St)/PVDF blend ultrafiltration membrane was prepared by blending and impregnation precipitation method with composite emulsion containing nano AgCl and Poly(MMA-St)copolymer as additive.The effects of microemulsion composition on the morphology,structure and properties of the blended ultrafiltration membrane were discussed:(1)When the amount of solubilized water(?),(MMA-St)oil phase medium,and the amount of composite emulsion added are constant,The effect of the composite emulsion containing nano AgCl and Poly(MMA-St)copolymers obtained under different CAgNO3 and CNaCl(CAgCl)on the morphology and structure of the blended ultrafiltration membrane is as follows.When CAgNO3 and CNacl(CAgCl)is low,the nano AgCl/Poly(MMA-St)composite emulsion is uniformly dispersed in the blended ultrafiltration membrane,and there is no obvious agglomeration.The size of nano AgCl is about 50 nm,and the shape is approximately spherical.The blended ultrafiltration membrane has an approximately elliptical pore cavity,and with the increase of CAgNO3 and CNaCl(CAgCl),the approximately elliptical pore cavity disappears in the blended ultrafiltration membrane,which grows into a narrower and more regular finger hole.Thus,we speculate that the presence of nano AgCl particles affects the formation of finger-like pores.In terms of membrane properties,when CAgcl?0.3 mol·L-1(CAOT =0.2 mol·L-1,co=2,VMMA:Vst =1:1,AgCl/Poly(MMA-St)polymerized emulsion is 15 wt%),With the increase of CAgCl,the porosity,hydrophilicity and anti-pollution performance of PVDF blend membranes increased.The porosity,water flux,water flux recovery rate,BSA retention rate and reversible pollution rate were respectively 70.6%,307.7 L· m-2 ·h-1,83.79%,78.2%,71.4%,about 2.3,3.8,1.6,1.28 and 2.0 times of the unblended PVDF hybrid membrane;when 0.3 mol·L-1<CAgCl ?0.5 mol·L-1,the porosity,hydrophilicity and anti-pollution performance of the blended ultrafiltration membranes decreased gradually.(2)In the case of the determinate CAnNO3 and CNaCl,(MMA-St)oil phase media content and the addition amount of composite emulsion,the results of the effect of the composite emulsion containing nanometer AgCl and Poly(MMA-St)copolymer on the blend ultrafiltration membrane were as follows:with the increase of the ?,the porosity,hydrophilicity and anti-pollution performance of the blend ultrafiltration membrane were slightly increased.The maximum porosity,water flux,water flux recovery rate,BSA retention rate and reversible contamination rate were 65.3%,228.7 L·m-2·h-1,60.0%,73.4%and 45.1%,respectively,which was about 2.16,2.84,1.15,1.2 and 1.26 times of the mixed PVDF supermembranes without blending.(3)In the case of the determinate CAgNo3 and CNaCL,solubilization of water(?),medium(MMA-St)oil phase content of must,affect of the different Poly real(MMA-St)composite emulsion copolymer content of blend ultrafiltration membrane morphology were as follows:When the addition amount of AgCl/Poly(MMA-St)composite emulsion is low(?15 wt%),the AgCl/Poly(MMA-St)composite is uniformly dispersed in the blended ultrafiltration membrane,and there is no obvious agglomeration phenomenon.The size of the nano AgCl is about 50 nm,and the shape is approximately spherical;When the addition amount of AgCl/Poly(MMA-St)composite emulsion is more than 15 wt%,the pore size of the blended ultrafiltration membrane is no longer circular or elliptical,but gradually exhibits irregular changes,and the ultrafiltration membrane pores are blended.There is a mutual connection between them,and the surface of the blended ultrafiltration membrane is also gradually rough and uneven.The AgCl/Poly(MMA-St)composite appeared very obvious reunion in the finger holes and sponge pores of the membrane.In the performance of blending ultrafiltration membrane,when the addition amount of AgCl/Poly(MMA-St)composite emulsion is low(?15wt%),with the increase of the addition amount of AgCl/Poly(MMA-St)composite emulsion,The porosity,hydrophilicity and anti-pollution performance of the blended ultrafiltration membranes increased,and the porosity,water flux,water flux recovery rate,BSA rejection rate and reversible pollution rate were 73.6%and 341 L·m-2·h-1,87.8%,81.2%,74.1%,respectively,about 2.4,4.2,1.7,1.33 and 2.1 times of the unblended PVDF hybrid membrane;when AgCl/Poly(MMA-St)polymerization When the amount of emulsion added was>15 wt%,the porosity,hydrophilicity and anti-pollution performance of the blended ultrafiltration membrane decreased.In addition,the addition of AgCl/Poly(MMA-St)composite emulsion promoted the conversion of PVDF from ???phase. |
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