We demonstrated that the reactivity of nano-sized zero-valent iron (nZVI) can be inhibited by magnetite for the reductive degradation of 1,1,1-trichloroethane (1,1,1-TCA) in nZVI/magnetite suspension under low content of nZVI. A remarkable reductive degradation of 1,1,1-TCA (0.289 h(-1)) was observed in nZVI (0.01 g/24 mL) suspension in 5 h, while no significant degradation was observed in nZVI (0.01 g)/magnetite (0.5 g) suspension in 80 h. The reductive dechlorination of 1,1,1-TCA in the nZVI/magnetite suspension started as the content of nZVI increased to 0.02 g. The slope of rate constant increase with respect to the nZVI content for nZVI suspension (17.67 g(-1), h(-1)) was greater than that for nZVI/magnetite suspension (14.89 g(-1) h(-1)) at the nZVI content between 0 and 0.1 g/24 mL No significant difference in the inhibition of nZVI reactivity by magnetite was observed in the pH range of 6-9. Surface analyses using transmission electron microscopy and X-ray photoelectron spectroscopy revealed that the significant increase of Fe(II) on the magnetite surface was due to an electron transfer from nZVI on its surface resulting in the inhibition of nZVI reactivity for the reductive degradation of 1,1,1-TCA in the nZVI/magnetite suspension. (c) 2010 Elsevier B.V. All rights reserved.