A comparative study of hexavalent chromium (Cr(VI)) removal from aqueous solution using Fe-0 and Fe3O4 particles in nano and micro-scale was performed. Our results indicated that the Cr(VI) removal efficiency using starch-stabilized Fe-0 nanoparticles, nonstabilized Fe-0 nanoparticles, Fe3O4 nanoparticles, Fe and Fe3O4 microparticles was 99.25%, 60.4%, 9.13%, 6.92% and 6.17%, respectively. Results revealed that the Cr(VI) removal efficiency using Fe3O4 particles was highly dependent on pH with maximum removal efficiency at pH 3. The stabilized Fe-0 nanoparticles efficiently remove Cr(VI) from aqueous solution in a wide pH range. In the present of Fe-0 nanoparticles, increasing the initial Cr(VI) concentration from 10 to 50 mg/L decreased removal efficiency and observed pseudo-first order rate constant (k(obs)) from 100% to 56.4%, and 0.101 to 0.015 min(-1), respectively. Increasing Fe-0 nanoparticles dosage from 0.1 to 2 g/L increased k(obs) value from 0.028 to 0.110 min(-1) and led to a 60% increase in the removal efficiency. The reaction rate constant decreased from 0.075 to 0.043 min(-1) with increasing pH from 3 to 9, respectively. Our results suggest that stabilized Fe-0 nanoparticles may serve as an effective agent for reductive removal of Cr(VI) from contaminated waters. (C) 2010 Elsevier B.V. All rights reserved.