Journal of Membrane Science 224 (2003) 11–28 Alumina and aluminate ultrafiltration membranes derived from alumina nanoparticles Kimberly A. DeFriend a,c , Mark R. Wiesner b,c , Andrew R. Barron a,c,∗ a Department of Chemistry, Rice University, MS-60, 6100 Main Street, Houston, TX 77005, USA b Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA c Center for Biological and Environmental Nanotechnology, Rice University, Houston, TX 77005, USA Received 20 December 2002; received in revised form 2 June 2003; accepted 16 June 2003 Abstract The fabrication of alumina ultrafiltration membranes using acetic acid surface stabilized alumina nanoparticles (A-alumoxanes) has been investigated. The pore size, pore size distribution, and molecular weight cut-off (MWCO) pa- rameters of the resulting membranes are highly dependant on the uniformity of the nanoparticle precursor, which is a function of the reaction time and reaction pH during their synthesis. By the control over the alumina nanoparticles, a significant im- provement of the membrane performance is observed over our prior results. The new alumoxane-derived membranes have a molecular weight cut-off in the range of <1000 g mol -1 , and show good selectivity to a range of synthetic dyes. Further control over selectivity and flux of these ceramic membranes may be obtained by the use of doped alumina nanoparticles (Fe, Mn, and La) that result in the formation of the appropriate aluminate membranes. Of these, LaAlO 3 shows the most promising results, with an increase in selectivity and increased flux as compared to the alumina analogue. Retention coefficients and flux values may also be altered by the chemical functionalization of the interior surface of the membranes by reacting the alumina surface with carboxylic acids. © 2003 Elsevier B.V. All rights reserved. Keywords: Ceramic membranes; Nanoparticle; Ultrafiltration; Synthetic dyes; Chemical functionalization 1. Introduction Previous research at Rice University has been aimed at understanding the control of ceramic porosity af- forded by the use of carboxylic acid surface stabilized alumina nanoparticles (carboxylate-alumoxanes) as ceramic precursors [1,2]. It was found that the pore size and pore size distribution is influenced by the selection of the organic substituent on the nanopar- ∗ Corresponding author. Tel.: +1-713-348-5610; fax: +1-713-348-5203. E-mail address: arb@rice.edu (A.R. Barron). URL: http://www.rice.edu/barron. ticle surface, while the average pore sizes may be altered through either physical or chemical mixtures of two (or more) carboxylate-alumoxanes [3]. Initial results provided alumina thin films with 20–50 nm intra-granular pores inside 2 m crystals [1]. Further studies allowed for reduction of the average pore size (8 nm) and pore size distribution by the use of smaller nanoparticles. Based on the ability to dip-coat sub- strates with alumoxane solutions to provide uniform defect free ceramic coatings [4,5], the fabrication of ceramic membranes was investigated [6,7]. Defect free asymmetric alumina ultrafiltration membranes (Fig. 1) with a thickness of ca. 2 m were prepared using acetic acid surface stabilized 0376-7388/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0376-7388(03)00344-2