Novel nanofiltration membrane with ultrathin zirconia film as selective layer

Thin film composite (TFC) membranes with ultrathin dense selective layer have emerged as a promising candidate for nanofiltration with excellent permeation and rejection performance. Herein, novel organic-inorganic TFC nanofiltration membranes (TFC NFMs) are fabricated via the mussel-inspired modification of ultrafiltration membrane followed by a mineralization process. Hydrolyzed polyacrylonitrile (HPAN) ultrafiltration membrane is facilely co-deposited with polydopamine (PDA) and polyetheylenimine (PEI), and the PDA-PEI coating further induces the growth of zirconia (ZrO2) nanoparticles on the membrane surface. The formed zirconia selective layer is defect-free, uniform, and ultrathin (10-20 nm). The organic-inorganic TFC NFMs show high retention ( > 90%) for bivalent cations with a salts rejection sequence of MgCl2 > CaCl2 > MgSO4 > NaCl > Na2SO4 at pH 6.0 ascribed to the positively charged membrane surface. The water flux reaches as high as 60 L/m(2) h under 0.6 MPa due to the ultrathin and hydrophilic properties of the inorganic selective layer. Moreover, the organic-inorganic TFC NFMs show good structure stability for long-term nanofiltration operation. (C) 2015 Elsevier B.V. All rights reserved.