Research On Preparation Of PDMS/PVDF Composite Membrane And Pervaporation Separation Properties For Phenol Water

Industrial waste water containing phenol which does great harm to natural water body has extensive sources.Compared with traditional biological treatment technology,pervaporation separation technology has a series of advantages such as low energy consumption,simple operation and small secondary pollution and so on.Pervaporation membrane materials is the core of pervaporation technology,but single pervaporation membrane materials can usually not completely satisfy the requirement of the target pollutants removal.In order to improve the film selectivity and the flux of organic matter,it is necessary to modify membrane materials.PVDF with a large flux,good separation effect and easy to clean,good membrane material,has been widely used.But further research should be done in its relatively properties of hydrophobic and easy swelling in organic matter.PDMS has excellent hydrophobic performance often used as the active layer of pervaporation membrane and commonly used in pervaporation membrane materials field.But its large-scale application is limited due to relatively poor film-forming ability and the selection of low permeability.In order to improve the selectivity of membrane and organic matter flux,the asymmetric PDMS and PVDF blending pervaporation membranes were prepared through phase transformation method in this paper.First of all,based on PVDF membrane materials,with DMAc as solvent,with PVP as the additive,PVDF flat membrane was prepared by phase transformation method.Water flux of film,entrapment rate,contact angle and mechanical strength were determined and characterized.The SEM observation was used to study the morphology structure of film.The influence on the membrane structure and performance of PVDF and PVP concentration,casting solution temperature,evaporation time and coagulation bath temperature were respectively investigated.The results showed that,PVDF flat membrane preparation conditions after the membrane performance strengthened: concentration of PVDF 18wt%,the PVP concentration 3wt%,casting solution temperature 50 ?,the evaporation time 40 s,coagulation bath temperature 20?.Secondly,after the strengthening of PVDF membrane system,PDMS/PVDF blend pervaporation flat membrane was prepared.By SEM,pore size analysis,contact Angle,mechanical properties,micro filter performance,infrared testing,EDS energy spectrum test,the influence of PDMS/PVDF mass ratio on blend flat membrane structure and performance were studied.After comprehensive consideration and analysis of experimental data,the PDMS/PVDF membrane with quality ratio of 1/10 had good morphology structure and larger contact Angle of 82.92°.Then,with the optimal reference to the PDMS/PVDF blend flat membrane system,based on PVDF membrane matrix and adding PDMS,blending PDMS/PVDF hollow fiber membrane was prepared.By SEM,contact Angle,mechanical properties,compression testing,micro filter performance,EDS energy spectrum test,thermogravimetric testing,XRD analysis,the influence of PDMS/PVDF mass ratio on blend hollow fiber membrane structure and performance were examined.Experiments show that the hollow fiber membrane comprehensive performance could be improved with PDMS/PVDF quality ratio of 1/20.Finally,flat membrane and hollow fiber membrane pervaporation membrane module were prepared,the PDMS/PVDF blend membrane were used in pervaporation process of water containing phenol,the effect on the properties of blend membrane pervaporation adding PDMS materials was explored.The influence of material liquid temperature,film pressure,material liquid velocity and other operating conditions on the properties of blend membrane pervaporation was also inspected.The research results showed that the addition of PDMS had greatly increased the pervaporation performance of the mixed membranes.PDMS/PVDF blend membrane had excellent comprehensive pervaporation performance.With vacuum degree of 60 k Pa,material liquid velocity of 2.0 L/min and feed liquid temperature of 50?,the membrane permeation flux could reach to 26.44 g/(m~2·h)with separation factor of 4.9.