Preparation And Application Of High Performance PVDF Ultrafiltration Membranes

Polyvinylidene fluoride(PVDF)is widely used in the preparation of ultrafiltration membranes due to its excellent mechanical properties,stable chemical properties,strong acid and alkali corrosion resistance and simple preparation process.However,polyvinylidene fluoride itself is a hydrophobic material,which causes problems such as contamination of the membrane and short service life of the membrane during use,so it is necessary to improve the hydrophilicity and improve the anti-pollution performance.In this paper,the preparation of high performance PVDF-g-PEGMA/PVDF ultrafiltration membrane was carried out by immersion precipitation phase transformation method.The hydrophilicity of the membrane is increased by the addition of an amphiphilic graft copolymer(PVDF-g-PEGMA),and the membrane resistance is increased by blending the composition of the coagulation bath with the carboxylated carbon nanotubes(CNT-COOH).Pollution performance.In this study,the flux of the membrane,the contact angle,the rejection,the adsorption of bovine serum albumin,and the characterization of the chemical composition and surface morphology of the membrane by FTIR,SEM and AFM were investigated.The effect of the addition on the structure and properties of the membrane yielded the following main conclusions.Firstly,the effect of NaCI concentration(0.00mol/L to 0.40mol/L)on the structure and properties of the membrane was investigated.The results show that the presence of NaCl in the coagulation bath will produce a salt-conducting effect,which can induce the enrichment of PVDF-g-PEGMA with hydrophilic groups on the surface of the membrane.By controlling the concentration of NaCl in the coagulation bath,it can play to a certain extent.The effect of adjusting the pore size and improving the hydrophilicity of the membrane surface.As the NaCl concentration increases,the surface roughness of the PVDF membrane gradually decreases,the hydrophilicity becomes stronger,the initial contact angle of the membrane becomes smaller and smaller,and the time taken for complete wetting becomes shorter and shorter,and the membrane is simultaneously.The size and distribution of surface pores are more unifonn;and as the concentration of NaCl coagulation bath increases,the flux of the membrane increases gradually.The maximum water flux of the membrane reaches 1711.99 L/m2·h,2558.65 L/n2·h.and 3738.89 L./m2·h,4168.21 L/m2·h,which is an order of magnitude higher than pure PVDF ultrafiltration membrane,but the retention rate is gradually reduced due to the larger menbrane pore size and porosity,but both are around 80%,of which M2 is due to pores.The uniform distribution and the smaller average pore size show better interception effect,and the removal rate reaches 89.27%.As the hydrophilicity increases,the anti-pollution performance of the membrane also shows a good effect.When the NaCl coagulation bath is 0.1 mol/L,the adsorption amount of bovine serum albumin is at least 32.91 ug/cm2,,which is smaller than that of pPure PVDF.More than doubled,the anti-pollution performance is the strongest.Considering the hydrophilicity,anti-pollution and recovery properties of the membrane,it is considered that the 0.10mol/L NaCl coagulation bath is the optimal condition for the preparation of PVDF-g-PEGMA/PVDF ultrafiltration membrane.Secondly,the effect of CNT-COOH dosage(0.01g to 0.04g)on the structure and properties of the membrane under optimal coagulation bath conditions was investigated.The results showed that PVDF-g-PEGMA/PVDF/CNT-COOH blended ultrafiltration membrane was prepared by using amphiphilic graft copolymer and carboxylated carbon nanotube as additive in 0.10mol/LNaCl coagulation bath.CNT-COOH The addition of the membrane pores becomes denser,the pore size becomes smaller,and the distribution is more uniform.By controlling the dosage of CNT-COOH,the effect of controlling the pore diameter and increasing the rejection rate can be achieved.With the increase of CNT-COOH dosage,the pore size of the membrane decreases first and then increases.The minimum pore size range is 21.34nm-46.42nm.When the dosage is 0.03g,the average pore size of the membrane is the smallest,and the removal rate of TOC is the smallest.Up to 92.68%,the retention rate of bovine serum albumin also reached 89.47%.The contact angle increases first and then decreases.When the dosage is 0.03g,the contact angle is 53.470.The formation of the hydrophilic layer on the surface of the membrane makes the pollutants not easily adsorbed on the surface of the membrane,and the anti-pollution performance of the membrane is greatly improved.The adsorption amount of bovine serum albumin was reduced to 28.8 ug/cm2.In addition,the addition of CNT-COOH increases the surface roughness of the membrane,which also increases the effective filtration area of the membrane,so that the pure water flux of the membrane is improved,and the hydrophilicity of the carbon nanotubes increases the hydrophilicity of the membrane.Carbon nanotubes have excellent mechanical properties.The addition of carboxylated carbon nanotubes greatly improves the recovery ability of the membrane.With the increase of carbon nanotubes,considering the hydrophilicity,anti-pollution performance and recovery performance of the membrane The PVDF-g-PEGMA/PVDF/CNT-COOH ultrafiltration membrane prepared by the NaCI coagulation bath was 0.10 nol/L,and the carboxylated carbon nanotubes were added at 0.03 g.