Poly(methyl methacrylate-methacrylic acid) P(MMA-MA) copolymer membranes were used in the filtration process to concentrate Fe(III) solutions. Suitable gelation period and thickness were determined, and transport properties of the membranes were modified using poly(ethylene glycol) (PEG) in the casting solution. The effects of pH and a complexable polymer [poly(vinyl alcohol) (PVA)] on the rejection of iron were investigated. Maximum recovery of 74% was obtained when the filtration was carried out in the presence of PVA at pH 3.1. (C) 1997 John Wiley & Sons, Inc.