Cross-linked carboxymethylated starch derivatives were synthesized and tested for their iron adsorbing capacity in aqueous solutions. To obtain the highly substituted carboxymethyl starch (CMS), a multi-step carboxymethylation process was adopted. The CMS with DS = 0.92 in aqueous medium was then exposed to electron beam radiation (EB) at various doses to yield the cross-linked carboxymethyl starch (CCMS). The CCMS of maximum gel content (87.1%) was obtained at 50 kGy with a 50% (w/v) aqueous CMS solution. The iron removal capacity of the CCMS was almost independent of the pH of the metal solution in the acidic range (pH 3-5), where the physical entrapment of the ion is dominant over a chelation reaction. The high physical entrapment was apparently associated with the high cross-link density. The adsorption capacity improved when the pH approached neutral but the iron showed complete precipitation at pH 7.