| Membrane separation technology is gradually being widely used as a water treatment technology, while "Membrane Fouling" which is one of the most important issue in the application process. So how to control the membrane fouling and improve the membrane anti-pollution capacity is becoming the most concern at present researchers research direction.Polyvinylidene fluoride(PVDF) due to its own relatively high physical and chemical properties and become the most popular film material. However, PVDF surface energy is low, showing more significantly hydrophobic, lead to PVDF ultrafiltration membrane is easy to be affected by water pollution in the process of water treatment. In this test, control the casting solution that PVDF concentration is between 8% to 18% to prepare the ultrafiltration membrane, The results show that The water flux of the membrane decreased with the increase of PVDF concentration; The PVDF ultrafiltration membrane rejection rate will gradually increase when PVDF concentration of between 8% to 14%, between 14% to 18% is basically stable. After comprehensive consideration two factors of water flux and rejection the PVDF concenotration is decided to be 12%. To improve the hydrophilic of the PVDF ultrafiltration membrane, The nano Mg(OH) 2 is added in the casting solution of PVDF UF membrane, and the matrix modification of the UF membrane was carried out, the preparation of the membrane was completed by the method of immersion gel phase transformation. Analysis The performance and structure of the preparation of PVDF/ Mg(OH) 2 modified ultrafiltration membrane. The purified water flux and rejection rate of the modified membrane were determined by the MSC-300 type ultrafiltration cup, The results showed that Nano Mg(OH) 2 particles modified ultrafiltration membrane is improved in the aspects of hydrophilicity and retention rate, The water flux of the modified membrane was increased to 333.37 L/(H m2) with the addition of nano Mg(OH) 2 particles content of 0.8%, compared with the unmodified membrane improved 126.32%, while the rejection rate can be maintained at 75.96%, water flux attenuation coefficient increased from 0.53 down to 0.34 after modification. Determination of wetting angle measured after the modified membrane wetting angle decreased to 59.31 °, showed significant hydrophilic properties.The membrane structure was analyzed by a relatively large scale instrument and equipment: The surface of the membrane and the structure of the cross section were observed by scanning electron microscope, and the roughness of the film surface was observed by atomic force microscope. The results showed that the prepared PVDF/Mg(OH) 2 composite modified membrane surface pore size compared to the unmodified PVDF ultrafiltration membrane increased, and the number of modified membrane pores also increased significantly. After the observation of the film section, it is found that the micro network pore structure of the modified membrane section is similar to that of the double layer. After AFM observation and comparison, the PVDF/Mg(OH) 2 composite modified film showed more concave and convex parts, it shows that the modified film has a further enhancement, thereby increasing the effective surface area of the ultrafiltration membrane. This structure can increase the water flux at the same time to ensure retention.However, there is no single state optimization for the improvement of the properties of the nanoparticles, when the nano- Mg(OH)2 addition amount of less than 0.8%, The hydrophilic property of the nanoparticles increased with the increase of the content of nano- Mg(OH)2, but when nano- Mg(OH)2 at the amount of 0.8% or more, It is easy to cause the aggregation of nanoparticles, which lead to large holes or defects in the film making, rejection of the film will rapidly decline, do not have practical value.Modified ultrafiltration membrane cooperated with A2/O process, To investigate the treatment effect and anti fouling property of modified PVDF UF membrane in practical application, the results showed tha The removal rate of COD in raw water can reach 37.8% and 56.1% respectively, respectively, after the treatment of the untreated UF membrane and the modified ultrafiltration membrane, And can significantly reduce the effluent turbidity, the turbidity of the effluent after ultrafiltration in 0.2NTU or so. Modified after the membrane water flux attenuation was lower than that of the non modified ultrafiltration membrane, indicating that the PVDF ultrafiltration membrane after nano Mg(OH) 2 particles blending modification of modified ultrafiltration in hydrophilicity and anti fouling of were better than that of the unmodified membrane. In cooperation with other water treatment process for the further deepening of domestic sewage treatment, for the ultrafiltration membrane application provides a certain reference value for the future. |
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