Preparation Of Zirconia Composite Ultrafiltration Membranes And Application In Seawater Desalination Pretreatment

Proper pretreatment is one of the most critical factors for the successful long-term performance of seawater reverse osmosis plant. Compared with the conventional pretreatment process, ultrafiltration (UF) pretreatment can effectively reduce SDI and turbidity from seawater, offer RO system with high and stable water supply and upgrade the reliability of RO system. The preparation methods of ZrO2 ultrafiltration composite membrane (ZUM) and the application of ZUM in the pretreatment of seawater desalinization were investigated in the dissertation.The high-grade ZrO2/Al2O3 composite ceramic ultrafiltration membranes were prepared with the modified sol-gel method. The influence of precipitator and stabilizing agent on the performance of sol and membranes were systematically studied. The surface morphology, phase transformation and character of gas permeation of the ZrO2 membranes were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), etc. It shows that carbamide as stabilizing agent is suitable for zirconium sol. Y2O3, CaO and CeO2 play a significant role in stabilizing the phase of zirconia because only the tetragonal zirconia existed at 800℃. Crack-free zirconia ultrafiltration membrane (ZUM) has an integrated surface and the most concentrative pore diameter of ZUM is about 25nm with a narrow distribution.Nanometer-sized power of yttria-stabilized zirconia (YSZ) was prepared by sol-gel method with zirconium oxychloride and yttria nitrate as the precursor. The structure, crystalline phase and particle size of YSZ were investigated. With polyethylene glycol (PEG) as dispersant, the stable suspension was prepared by ultrasonic dispersion of YSZ nanometer powders. Then, tubular ZrO2/Al2O3 composite membrane whose most concentrative pore diameter was about 42nm was prepared by dip coating.Self-made ZrO2 ceramic ultrafiltration composite membrane was applicated for desalinization pretreatment. The quality of ultrafiltration-water meet the reverse osmosis membrane entering water requirement(GB/T19249-2003) far effectively. The technic can slow down the membrane pollution and prolong the life of membrane. The results showed that, under the experimental conditions, the membrane flux of permeation reached 65L/m2·h, turbidity of permeant water reached below 0.15NTUand SDI below 0.25.