Study On The Equipment And Technology Of Preparaing PVDF Separation Membrane And Its Photocatalytic Modification

Polyvinylidene fluoride(PVDF) is a semi-crystalline polymer with excellent corrosion resistance, chemical stability and film-forming properties, and has been used widely in membrane separation technology, but the application PVDF membrane is limited by organic pollution in filtration. The flat membrane casting equipment and casting film fluid composition have an important influence on Polyvinylidene fluoride separation membrane performance, so improving equipment and formula has an significant significance to Polyvinylidene fluoride separation membrane.This paper first complete flat membrane casting equipment design, than use this equipment to preparing PVDF membrane and Ti O2-PVDF membrane, and the optimization of the hybrid photocatalytic modified PVDF membrane The main research content is as follows:Firstly, in consideration of the low accuracy and efficiency of small-sized flat membrane casting equipment, a new flat membrane casting equipment was design in this paper. In the design, The thickness can be adjusted by a precise adjusting knob, and gel water bath and guiding roller can assist to complete continuous blowing membrane. In order to ensure the precision of membrane, the liner velocity is kept constant by motor and speed online regulating device.By using self-design lat membrane casting equipment is to improve pollution resistance of PVDF membrane. The effect of PVDF content and PEG-6000 content on membrane’s performance was explored, then the optimal formula was added Ti O2 and modified by photocatalysis. The influence of content of Ti O2 on membrane was studied. In order to improve the dispersion of Ti O2 in casting solution, Ti O2 sol was prepared, and compared with effect of adding Ti O2 only, adding Ti O2 and dispersant into casting solution on membrane performance. Finally, the effect of light intensity, illumination time, filtrate PH value and filtrate concentration on photocatalysis on membrane pollution resistance.The result shows:1) The self-designed flat membrane casting equipment with high precision of membrane thickness, the thickness can be adjusted accuracy of 1um, maximum casting speed of 2.0 m/min, gel bath time can be controlled.2) The excellent membrane can be get with mass fraction 22% PVDF, 12.5% PEG-6000, which water flux and pepsin resistance have reached 1270 L/(m2?h?bar) and 68%.3) Casting membrane solution with 0.5% Ti O2 has a good film-forming performance, modified membranes have a certain degree of improvement in thermal stability, et al; By preparing Ti O2 sol can improve Ti O2 dispersion in casting membrane solution, by EDS, a Ti element weight percentage of Ti O2 sol modified membrane surface reached 4.66%, which is the highest of the three modified membranes.4) During photocatalytic UV irradiation experiments, Ti O2 modified membranes shows self-purification properties, under UV irradiation(1m W/cm2), modified separation membrane flux recovery more than 20%, the pure PVDF membrane flux is 1%, 1m W/cm2 is the best light intensity of such Ti O2 modified membranes; when PH=7, the photocatalytic Ti O2 photocatalytic modified membranes shows best optimal performance; at the same time, when humic acid concentration of 0.5mg / L, the separation membrane flux attenuation minimum.