Electric field assisted layer-by-layer assembly of graphene oxide containing nanofiltration membrane

Abstract

An external electric field (EF) was applied to assist the preparation of graphene oxide (GO) and polyethyleneimine (PEI) layer-by-layer films on hydrolyzed polyacrylonitrile (H-PAN) substrate. The property and structure of the resultant membranes were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM), electrokinetic analyzer and water contact angle goniometer. The effect of assembly conditions (e.g. EF voltage, deposition time, GO concentration and number of PEI/GO bilayers) on nanofiltration (NF) performance of LbL membranes was systematically investigated. The optimized preparation conditions were 5V EF voltage, 3min deposition time, 0.025mg/ml GO, and 2 PEI/GO bilayers. The resultant EF assisted LbL membrane exhibited a flux of 65.6lm−2h−1 and a rejection of 80.9% to 0.5g/l MgCl2 at 0.40MPa. Salts rejection of LbL2.0 membrane followed the sequence of Na2SO4>MgSO4>MgCl2>NaCl, which indicated that the membrane surface was negatively charged with GO as the outmost layer. It was also demonstrated that the EF enabled denser and more ordered pack of PEI and GO layer, resulting in higher stability than the PEI/GO membrane prepared without EF. Our work not only offered an efficient approach for GO based membrane assembly and hereby provided a stable and high performance GO− containing NF membrane, but also paved a new way towards the design of nanomaterials contained membranes.