Journal of Membrane Science 246 (2005) 137–144 Characterization of BSA-fouling of ion-exchange membrane systems using a subtraction technique for lumped data J.-S. Park a,1 , T.C. Chilcott b , H.G.L. Coster b , S.-H. Moon a,∗ a Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea b UNESCO Centre for Membrane Science and Technology and Biophysics, School of Physics, The University of New South Wales, Sydney 2052, NSW, Australia Received 12 February 2004; received in revised form 28 July 2004; accepted 30 July 2004 Available online 24 November 2004 Abstract Electrical impedance spectroscopy (EIS) techniques were used to gain insight into BSA fouling of the Neosepta CMX and AMX ion- exchange membranes (IEMs). EIS characterizations were made at concentrations above 0.1 M KCl because the conductance of the IEMs was higher than that of bulk solutions of concentration below 0.1 M KCl. Spectra, expressed in terms of dispersions of the conductance and capacitance with frequency, provided an enhanced indication of IEM fouling during separation processes. Bulk conductance measurements of the solution alone, membrane immersed in solution and fouled membrane immersed in solution showed good agreement with general theoretical predictions. Strong dispersions in capacitance were observed below 1 kHz for each of these configurations. Differences in the dispersions arising from fouling were identified by subtracting the impedance of the solution from those of unfouled and fouled IEMs in solution. The conductance and capacitance dispersions of fouled IEMs decreased with the accumulation of the BSA fouling layer on the surface. © 2004 Elsevier B.V. All rights reserved. Keywords: Fouling; Cation-exchange membrane; Anion-exchange membrane; Impedance spectroscopy; Bovine serum albumin 1. Introduction Electro-membrane processes using ion-exchange mem- branes have been widely used in numerous applications [1–8]. Although ion-exchange membranes have proven very use- ful, prevention of their fouling remains one of the essential problems to overcome in their design and operation. Fouling causes deterioration in the membrane performance such as a decline in the flux and an increase in the electric resistance [9–12]. The macromolecular bovine serum albumin (BSA) ∗ Corresponding author. Tel.: +82 62 970 2435; fax: +82 62 970 2434. E-mail addresses: park@kier.re.kr (J.-S. Park), shmoon@gist.ac.kr (S.-H. Moon). 1 Present address: Fuel Cell Research Center, Korea Institute of Energy Research (KIER), 71-2 Jang-dong Yusong-gu, Daejeon 305-343, South Ko- rea. Tel.: +82 42 860 3548; fax: +82 42 860 3309. deposits on the surface of cation- and anion-exchange mem- branes depending on solution pH. Hence, it is important to evaluate electrochemical properties of these membranes and develop methods to monitor separation processes during their operation in order to minimize fouling. Many researchers have reported that decreases in the in- trinsic conductivity of membranes in real time indicated membrane fouling. However, such decreases can also be due to dilution of the ions in compartments of the membrane or near the membrane surface, physical defect in the membranes or chemical damage of membranes during operations. Watkins and Pfromm [13] used capacitance spectroscopy to characterize the fouling process in anion-exchange mem- brane systems. The capacitance of the fouled anion-exchange membrane increased with decreasing frequency to a larger extent than that of the unfouled one. 0376-7388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2004.07.022