The removal of Fe(III) ions from aqueous solutions was studied using membrane filtration. A water-soluble polymer alginic acid (AA) was used to bind the metal ions, which was followed by batch ultrafiltration using poly(methyl methacrylate-methacrylic acid) membranes modified with poly(ethylene glycol) (PMMA-MA-PEG). The complexation behavior of AA and the effect pH on the rejection of iron were investigated. Maximum recovery of 87.13% was obtained when the filtration was carried out in the presence of AA at pH 3.1.