Study On The Preparation Of The PVDF/TiO₂ Nano Blending Membrane Supported By Fabric And Its Anti-Fouling Performance In MBR

Because of the incomparable advantages to traditional wastewater treatment process, the high efficient and useful treatment process named MBR that consist of microbial degradation of pollutants and membrane separation technology is attracting attention of water treatment researchers in the world. But the expensive membrane filtration module and the issue of membrane fouling are the major obstacles to the wide application of MBRs. So the research to membrane materials and the method to reduce membrane fouling are very valuable to use in practical application.In this experiment, the low prices filter material called nylon fabric was used to be the supported layer of polymer membrane materials to instead of the traditional membrane materials. TiO2 was added to the PVDF membrane which mainly used PVDF and DMAC to make the PVDF/TiO2 blending membrane that can dispose the life sewage. This article is mainly from the following several aspects of research:(1) The PVDF/NANO TiO2 blending membrane that supported by the nylon fabric was made with the Immersion Precipitation. Testing the water flux of membrane and BSA interception rat and analyzing the membrane surface structure with SEM to confirm the formula of membrane that can get the PVDF/TiO2 blending membrane with larger water flux, correct interception rat and well-proportioned membrane. There was a PVDF/TiO2 blending membrane preparation plan according to the single factor analysis of experimental results:the Solid content of PVDF was 10%, DMAC was the solvent, add 0.7%NANO TiO2, choosing the 200 mesh nylon fabric as the bottom supporting layer. The PVDF/NANO TiO2 blending membrane made on this occasion had the best water flux that nearly five times as high under the same conditions when the temperature was 25℃and the pressure was 0.1 MPa.(2)The membrane was used in the MBR to filter activated sludge in order to get the membrane module that had better water flux and flow effect. In this experiment, the best blending membrane project is:the Solid content of PVDF was 10%, DMAC was the solvent, add 0.7%NANO TiO2, choosing the 200 mesh nylon weaving as the bottom supporting layer. When at room temperature and 0.1 MPa press the PVDF/0.7%NANO TiO2 blending membrane had the best water flux and was the most effective one to intercept organic. Considering the production budget, the cost to the PVDF/0.7%NANO TiO2 blending membrane was much less than the commercial membrane. Moreover, the sewage flux to the blending membrane was much better than the normal PVDF membrane.(3)The PVDF membrane, PVDF/0.7% NANO TiO2 mixed membrane and PVDF/1.0% NANO TiO2 blending membrane that supported by nylon fabric were mingled in the MBR to analysis the mechanism of membrane fouling and tested the sewage flux, the rate of flux descending, the distribution of total resistance and the recovery rate of flux after cleaning, then further researched the performance of the membrane to resist the pollution.With the extension of time the experimental results show that the sewage flux of PVDF membrane, PVDF/0.7% NANO TiO2 blending membrane and PVDF/1.0% NANO TiO2 blending membrane were all reduced when the membrane resistance increased. Comparing these membranes, the resistance and the flux's variation rate of the PVDF/0.7% NANO TiO2 blending membrane were the lowest, so some NANO TiO2 had certain effect on delaying pollution. The blocking of membrane hole was the mean reason to pollute the membrane that running in a short time. After long-time membrane resistance analysis, the main reason to the membrane resistance of PVDF membrane and PVDF/0.7% NANO TiO2 blending membrane was the membrane internal pollution which meant membrane blocked hole. Secondly, the formation of concentration polarization layer and gel layer was the reason to increase resistance. Moreover, the membrane fouling of the PVDF/1.0% NANO TiO2 blending membrane were made by the resistance of blocked hole and the sedimentary layer. Through aggregate analysis, the PVDF/0.7% NANO TiO2 blending membrane had certain practical value because its great flux, well retention rate and strong anti-fouling capability.