Journal of Membrane Science 403–404 (2012) 227–235 Contents lists available at SciVerse ScienceDirect Journal of Membrane Science jo u rn al hom epa ge: www.elsevier.com/locate/memsci Combined effects of operational parameters on electro-ultrafiltration process characteristics Maryam Hakimhashemi a,∗ , Abaynesh Yihdego Gebreyohannes a , Hans Saveyn a , Paul Van der Meeren a , Arne Verliefde a,b a Ghent University, Faculty of Bioscience Engineering, Department of Applied Analytical and Physical Chemistry, Particle and Interfacial Technology Group, Coupure Links 653, B-9000 Ghent, Belgium b Delft University of Technology, Faculty of Civil and Environmental Engineering, Department of Sanitary Engineering, Stevinweg 1, 2628 CN Delft, the Netherlands a r t i c l e i n f o Article history: Received 27 December 2011 Received in revised form 22 February 2012 Accepted 24 February 2012 Available online 6 March 2012 Keywords: Crossflow electro-ultrafiltration Flux improvement pH Conductivity Alumina a b s t r a c t The aim of the present study was to identify the influence of process parameters and their interactions on the electro-ultrafiltration performance during the filtration of alumina suspensions at low cross-flow rates. Overall, a weak flux-pressure dependence was observed in the absence of an electric field, indicating mass transfer limitation. A clear enhancement of flux was achieved by superimposing an electric field on the transmembrane pressure. As the feed pH increased from the acidic range to the vicinity of the isoelectric point of the particles, the beneficial effect of the electric field on permeate flux decreased significantly. Statistical analyses showed that in addition to the experimental parameters, some of their interactions were quite influential for determining the performance of the electro-ultrafiltration (EUF) process. Thus, the electric field induced flux enhancement became less pronounced as the initial ionic strength of the feed solution increased. In addition, the three studied response factors were noticed to be interrelated, whereby inevitable pH and conductivity changes associated with the electrode reactions during the electrofiltration process were also important in determining the permeate flux and quality. Overall, the results indicated that a clear understanding of the EUF performance is only possible when considering different effects (such as flux improvement and pH shift) simultaneously. © 2012 Elsevier B.V. All rights reserved. 1. Introduction In many membrane processes, particles are separated on the basis of their size and shape using pressure, and specially designed semi-permeable membranes [1]. More stringent environmental legislations, together with the possibility of cost-comparable and more energy-efficient application, have made membrane separa- tion an attractive and promising technology in many wastewater reclamation and drinking water production utilities. According to Scholz and Lucas [2], the possibility of zero pollutant discharge becomes more realistic in the future by applying membrane sepa- ration. However, the efficient use of membrane technology requires consideration of membrane fouling and concentration polarization as these both determine the economical and technical feasibility of the process [3]. Electro-ultrafiltration (EUF) is a process in which ∗ Corresponding author. Tel.: +32 9 264 99 43; fax: +32 9 264 62 42. E-mail address: Maryam.Hakimhashemi@UGent.be (M. Hakimhashemi). charged solutes are taken away from the surface of the membrane by applying an electric field and hence, it opens perspectives to reduce concentration polarization and fouling [4]. Many researchers have investigated this technology for differ- ent applications. For example, Weng et al. [5] investigated the application of EUF for the treatment of water containing arsenic. They reported that arsenic rejection increased from 30% to 90% by applying a dc electric field. According to Weigert et al. [6], an elec- tric field improved the permeate flux during filtration of cristobalite and baker’s yeast by ten- and six-fold, respectively. Kim et al. [7] examined the effect of electric field application on the reduction of fouling, inactivation of microorganisms and the enhancement of particle coagulation for fresh sewage. They found that the coagu- lant (poly aluminum chloride) dose for the 95% removal of turbidity could be reduced by about 75% by applying 10 kV/cm electric field. The two major electrokinetic phenomena that control EUF are electrophoresis and electro-osmosis. Electrophoresis is the move- ment of particles relative to a stationary fluid due to an applied electric field [8,9], which may prevent particles from depositing on the membrane by changing the direction of their movement [10]. Upon imposing an external electric field across a porous matrix, 0376-7388/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2012.02.054