Studies On Preparation And Performance Of Nanowire Modified PVDF Ultrafiltration Membrane

As an environment-friendly membrane separation technology,ultrafiltration has wide application prospect.Polyvinylidene fluoride(PVDF)is a common industrial membranous materials with significant advantages in mechanical strength and stability.However,a large number of C-F bonds and C-H bonds on the surface determined its hydrophobicity which made the oil pollutants can easily be adsorbed on the membrane surface and caused membrane fouling in the separation process,and finally reduced the flux and shortened the service life.So the membrane fouling problem is the bottleneck in the further development of membrane separation technology.It was found that adding hydrophilic inorganic nanomaterials to PVDF membrane can greatly improve the hydrophilicity of PVDF membrane surface and reduce membrane fouling.At the same time,the modified membrane was prepared via combining the one-dimensional nanomaterial with the PVDF casting solution not only has the advantages of both organic polymer and inorganic materials to make up for its defects,but also could produce strong interface effect.This has become a hot topic in recent years.In this paper,Cu(OH)2,Mn O2 and V2O5 nanowires with superhydrophilic properties were synthesized and be blended into PVDF casting solution as hydrophilic modifier to prepare the Cu(OH)2-PVDF,Mn O2-PVDF and V2O5-PVDF modified hybrid ultrafiltration membranes,respectively.In addition,the changes of microstructure and macroscopic separation properties of PVDF ultrafiltration membrane were studied systematically.Blending Cu(OH)2 nanowires(synthesized by chemical precipitation method)with PVDF and porogen PVP in DMAc solvents directly to prepare the Cu(OH)2-PVDF modified membrane with different modifier content by immersion-precipitation phase transformation.The results show that the ultrafiltration membrane had high retention rate before and after modification.In addition,the hydrophilicity,anti-pollution performance and penetration flux of the modified PVDF ultrafiltration membrane all have been improved compared with pure PVDFmembrane,and the optimal addition of Cu(OH)2 nanowires is 1.2 wt%,when the pure water flux of the membrane reached to 508.02 L·(m2·h)-1 from 336.90 L·(m2·h)-1,the water flux recovery rate increased by nearly 20 % and the retention rate of BSA was as high as 100 %.It also achieved remarkable results in the oil-water separation experiment.The superhydrophilic Mn O2 nanowires,which were synthesized by hydrothermal method were used as modifier to prepare Mn O2-PVDF modified membrane with different nanowires content.According to the investigation of the structure and performance of Mn O2-PVDF modified ultrafiltration membrane,it was known that the surface hydrophilicity of the modified membrane was enhanced as well as the water flux recovery rate with the increase of Mn O2 addition.Besides,The filtration performance of modified ultrafiltration membrane was optimal when the addition of nanowires was 1.5 wt%,by this time the BSA retention rate and oil retention rate were also kept higher value.PVDF ultrafiltration membrane was modified with homemade V2O5 nanowire to prepare the V2O5-PVDF modified membranes.Through investigated the effects of modifier addition on the porosity and pore size,contact angle,permeation flux and surface roughness of the membrane can found that the porosity and pore size of the membranes increasing gradually with the increase of the V2O5 nanowires addition.At the same time,the hydrophilicity of membrane was improved gradually,so the permeation flux and anti-pollution performance are also improved.