Chemical Engineering Science 58 (2003) 5291–5298 www.elsevier.com/locate/ces Polymer adsorption on multicomponent surfaces with relevance to membrane fouling Simcha Srebnik * Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel Received 12 June 2001; received in revised form 9 July 2002; accepted 15 May 2003 Abstract Block copolymer thin lms that include low surface energy domains are analyzed as a possible way to overcome the problem of membrane fouling by proteins and other natural organic matter. A model is presented that accounts for both fouling due to chemical interactions between the solute and surface and due to convective deposition. Guidelines for the formation of novel membranes with improved fouling-resistant properties are suggested based on comparison of the relative permeate ux decline due to fouling on dierent model copolymer membranes. In general, it is observed that copolymer lms having small and dispersed polymer blocks that interact unfavorably with the fouling species show an overall decrease in fouling and increase in permeate ux compared with the homopolymer lms. ? 2003 Elsevier Ltd. All rights reserved. Keywords: Adsorption; Fouling; Deposition; Membranes; Modeling; Filtration 1. Introduction Membranes are extensively used in a wide variety of separation processes in various applications and industries including water treatment, agro-food industries, pharmaceu- ticals, and biomedical applications such as articial organs, drugs, and biosensors. In many of these applications, a prob- lem that is often encountered is the deposition of fouling material on the membrane surface or in its pores, leading to blocking of the pores. With time and increased opera- tion pressure, permeate ux reaches an asymptotic value be- yond which further increase in pressure does not increase the ux. Consequently, in order to continue at acceptable levels of operation the membrane must be cleaned, or even replaced if irreversible fouling occurs. As an alternative to cleaning, membrane research today increasingly focuses on various solution pretreatments or membrane modication methods to retain a clean surface during normal operating conditions. Considerable research is being devoted towards modify- ing the surface properties of composite membranes, where the nature of the membrane is altered so that the adhesive or ∗ Fax: +972-4-829-5676. E-mail address: simchas@tx.technion.ac.il (S. Srebnik). adsorptive forces between the membrane and the solute are minimized. Numerous studies on specic membrane-solute systems have been carried out with mostly encouraging results showing that specic chemical and physical mod- ications of the membrane’s surface reduce fouling (e.g., Stengaard, 1988; Nystr om and J arvinen, 1991; Yamagishi et al., 1995; Ulbricht and Belfort, 1996; Mueller and Davis, 1996; Belfer et al., 2000). However, although these studies provide some information on the mechanism of adsorp- tion, in general each new membrane-solute system must be individually analyzed since the current experimental approaches treat fouling as a solute dependent process. Hence, the goal of this paper is to provide some general indications for the preparation of fouling-resistant modi- ed membranes. A simple model is presented that captures general qualitative characteristics of the membrane-solute system. Fouling can be caused by various mechanisms including chemical binding, short-ranged forces, electrostatic attrac- tive forces, or convective deposition. The extent to which these factors contribute depends on the nature of the fouling particles, the solution properties and the membrane material. Fouling by proteins and other natural organic matter (NOM) presents an especially dicult problem due to the inher- ently complex nature of the solutes. Indeed, the processes 0009-2509/$ - see front matter ? 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.ces.2003.05.008