The Study On Preparation Of TiO₂/PVDF Modifying Hollow Fiber Ultrafiltration Membrane And Its Separation Performance Of Typical Pollutants In Water

The PVDF/PVP/Li Cl blend hollow fiber ultrafiltration membrane was modified by adding different nanosized TiO2 content using non-solvent phase induce separation method. The effect of spinning conditions on the morphology and performance of the modified membrane were investigated. Also, bovine serum albumin(BSA) and sodium alginate(SA) was used as a representative protein and porlysaccharide substance,respectively. The influence of BSA, SA and BSA-SA binary solutions on separation performance and factors were investigated by using TiO2/PVDF modified membrane prepared by the optimal conditions. The main conclusions were showed as follows:(1) The typical asymmetric cross-section structures were formed with adding TiO2 nanoparticles, exhibiting a two-layer finger-like structure extended to the middle of the cross-section, and the dense inner shin layers of the porous network structures were also formed, respectively. With the increase of the TiO2 content, both inner and outer surfaces skin layer were thicker, and the numbers of finger-like morphology decreased.Meanwhile, the pure water flux of modified membrane decreased, BSA rejection rate increased, the tensile strength and elongation at break also increased, the membrane surface hydrophilicity reduced.(2) With the increase of bore liquid temperature, the pure water flux of modified membrane increased, and BSA rejection decreased, the tensile strength and fracture growth rate increased. With increasing of coagulation bath temperature, the water flux of the modified membranes exhibit decreased, while the BSA rejection rate increased first and then decreased, the overall decreasing trend, the tensile strength and elongationat break increased. With the prolonged air gap, the pure water flux of the modified membrane showed a downward trend,while BSA rejection rate is showing a decreasing trend after the first increases,the tensile strength and elongation at break are showing an increasing trend.(3) The TiO2/PVDF blend modified hollow fiber membrane with adding 1% TiO2 exhibited the best performance when the spinning conditions for bore liquid temperature was 40?, the external coagulation bath temperature was 20?, and air gap was 10 cm.Its pure water flux reached 612.54L/(m2·h), BSA rejection rate reached 94.7%, the tensile strength of 2.73 MPa, elongation at break is 187%.(4) With increasing concentration of the BSA, SA, BSA-SA binary solution,fouling on membranes were increased, SA was the superiority foulants in binary solution. BSA-SA binary solution on membrane pollution was most serious, and increased with the increasing of the SA content in solution, SA solution followed, BSA solution lightest. The fouling irreversible of the membrane was on the contrary, its showed follow the order of : BSA>BSA-SA>SA.(5) The effect of BSA solution with different pH values on the fouling of the modified membrane showed follow the order of: pH5 > pH7 > pH3 > pH9 > pH11. As the pH value of SA solution increased, SA fouling on the membrane gradually reduced.The effect of BSA-SA binary solution with different pH values on the fouling of the modified membrane showed follow the order of: pH7 > pH9 > pH11 > pH5 > pH3.(6) With the increase of ionic strength of the solution, BSA, SA, BSA-SA binary solutions on the membrane fouling were reduced. However, with increasing the ionic strength of the SA and BSA-SA binary solution, the fouling irreversibility of membranes were slightly heavier.