Preparation Of Composite Ultrafiltration Membrane By PVDF And TiO₂ Nanoparticles

Membrane technology is one of the preferable ways for drinking water treatment in the 21st century. The pollutants in raw water can be removed when ultrafiltration (UF) is combined with conventional water treatment process. The quality of domestic UF membranes still need improving and is not widely used in water treatment plant due to costs. Therefore, research in UF membrane technology has great significance of theoretical and practical values.The most concentrated research focused on UF membranes is to enhance anti-fouling property and to reduce costs. Though costly, polyvinylidene fluoride (PVDF) has excellent thermal and chemical stability. Nano materials are considered as one of the most prospective material among new type materials. PVDF and TiO₂ nanoparticles were chosen to develop UF membranes with good anti-fouling performance for water treatment. PVDF UF membrane and PVDF-TiO₂ composite UF membranes were prepared by a phase inversion method. The effect of casting solution compositions and preparation conditions on membrane structure and performance was discussed. Modern instrumental analysis was used to investigate the membrane surface, cross-section and inner section.14%¹8% PVDF in the casting solution was appropriate to prepare PVDF UF membrane. Based on former studies, the effect of low LiCl concentration in casting solution (w(LiCl)) on membrane structure and performance was studied. PVDF membrane made from casting solution containing 16% PVDF and 0.05% LiCl was the thinnest, and it had the least flux (F) and flux reduction coefficients (m) and the most rejection (R) of blood serum albumen (BSA) under the experimental conditions. When w(LiCl) was less than 0.05%, F and m of the prepared membrane decreased with increasing w(LiCl), while R increased. However, when w(LiCl) was more than 0.05%, F and m of the prepared membrane increased with increasing w(LiCl), while R decreased. PAN UF membrane had the same phenomena. For example, PAN membrane made from the casting solution containing 18% PAN and 1% LiCl was the thinnest, and it had the least F and m and had the highest R under the experimental conditions.