Journal of Membrane Science 235 (2004) 73–86 Preparation and performance of cellulose acetate/polyethyleneimine blend microfiltration membranes and their applications Zhaoan Chen a,b,∗ , Maicun Deng a,b , Yong Chen a,b , Gaohong He a,c , Ming Wu a,b , Junde Wang b a National Engineering Research Center of Membrane Technology, 457 Zhongshan Road, Dalian 116023, China b Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China c School of Chemical Engineering, Dalian University of Technology, Dalian 116012, China Received 27 August 2003; received in revised form 29 January 2004; accepted 31 January 2004 Abstract A modified microfiltration membrane has been prepared by blending a matrix polymer with a functional polymer. Cellulose acetate (CA) was blended with polyethyleneimine (PEI), which was then crosslinked by polyisocyanate, in a mixture of solvents. In the membrane, PEI can supply coupling sites for ligands in affinity separation or be used as ligands for metal chelating, removal of endotoxin or ion exchange. The effects of the time of phase inversion induced by water vapor, blended amount of PEI and amount of crosslinking agent on membrane performance were investigated. The prepared blend membranes have specific surface area of 12.04–24.11 m 2 /g and pure water flux (PWF) of 10–50 ml/cm 2 min with porosity of 63–75%. The membranes, made of 0.15 50 wt.% PEI/CA ratio and 0.5 crosslinking agent/PEI ratio, were applied to adsorbing Cu 2+ and bovine serum albumin (BSA) individually. The maximum adsorption capacity of Cu 2+ ion on the blend membrane is 7.42 mg/g dry membrane. The maximum adsorption capacities of BSA on the membranes with and without chelating Cu 2+ ion are 86.6 and 43.8 mg/g dry membrane, respectively. © 2004 Elsevier B.V. All rights reserved. Keywords: Polyethyleneimine; Blend membrane; Crosslink; Surface modification; Adsorptive membrane 1. Introduction Rapid developments in biotechnology and the pharmaceu- tical potential of biomolecules have brought great demand for reliable, efficient methods to purify preparative amounts of proteins, peptides and nucleic acids [1–3]. Membrane fil- tration can meet the demand and is used in bioprocess re- covery to remove cell debris, colloidal or suspended solids and virus particles from homogenized suspensions of bacte- rial cells [2]. In recent years, polymeric membrane materials with functional groups have gained more attention because through chemical modification, ligands intended for affinity, pseudo-affinity, ion exchange, etc. can be coupled to func- tional groups in membrane substrates to adsorb biomolecules selectively in the filtrate [2–4]. Thus, modified membrane is ∗ Corresponding author. Tel.: +86-411-4379223; fax: +86-411-4677947. E-mail address: zachen@dicp.ac.cn (Z. Chen). called as adsorptive membrane or membrane adsorber. Ad- sorptive membrane chromatography reflects technological advances in both membrane filtration and fixed-bed liquid chromatography. Dissolved molecules are carried directly to adsorptive sites in these membranes by convective flow, eliminating the long diffusion time required by resin-based chromatography. This adaptation increases the throughput of adsorption processes [5]. Based on the analysis of the adsorption kinetics [6–9], basic membranes should have homogeneously microp- orous/macroporous structure with a large internal surface area, high interconnectivity and mechanical stability, which is usually owed to the feature of microfiltration membrane. Adsorptive membrane substrates should be mechanically resilient and resistant to solvents used to activate coupling and not participate in secondary hydrophobic adsorp- tion, which produces non-specific retention that interferes with product resolution or can lead to the denaturation of biopolymers. Most of the polymers used in manufacturing 0376-7388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2004.01.024