In this study, an antibacterial ultrafiltration (UF) membrane was developed by depositing polyethyleneimine (PEI) onto a microporous polyacrylonitrile (PAN) membrane surface via the electrostatic self-assembly followed by immobilization of copper (II) ions on the membrane surface. The resulting PAN-PEI-Cu membrane showed an improved separation performance, copper stability and antibacterial properties. The filtration experiments indicated that the resulting membrane exhibited a steady-state flux of 63 L/(m(2) h) and a rejection of 91% for a feed containing 5 mg/L humic acid (HA) at 0.16 MPa. In addition, an atomic absorption spectrophotometer (AAS) was used to monitor the release of copper ions from the membrane driven by various chelating solutions. It was found that copper on the membrane could still act effectively as a biocide for long-tem operation in raw seawater. Furthermore, the membrane exhibited an antibacterial efficiency of 71.5% against Escherichia coli. This modification technique is simple and practical because dilute solutions are used for surface treatment and commercial membrane units can be modified in their original modules. The membrane is considered to be suitable for such applications as ultrafiltration for pretreatment of seawater desalination. (C) 2012 Elsevier B.V. All rights reserved.