Polyvinylidene fluoride (PVDF) ultrafiltration membranes modified by nano-ZnO are prepared by phase inversion method to improve their hydrophilicity and enhance application in water treatment. The effects of nano-ZnO amount on the structure and performances of the membranes are investigated. The porosity, hydrophilicity, microstructure, mechanical strength, pure water flux, protein rejection and flux recovery efficiency are characterized by porosity measurement, contact angle measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), mechanical property test and ultrafiltration experiments, respectively. The results show the following. When the mass fraction of nano-ZnO is 0.2%, the contact angle of the membrane is decreased from 76.3° to 63.4°, indicating a significant hydrophilic improvement. The porosity increases from 53.4% to 54.1% and the tensile strength increases from 2.09 MPa to 2.82 MPa. Pure water flux, protein rejection and flux recovery efficiency are improved to a certain degree. The cross-section structure of the membrane is regular, the size of finger-like hole is large and the surface of the membrane is smooth.

phase inversion method  /  polyvinylidene fluoride  /  ultrafiltration membrane  /  nano-ZnO