Abstract In this study, a commercial aqueous dispersion of nZVI was applied for the removal of Cd(II), Cu(II), Ni(II), and Pb(II) ions from their aqueous solutions. The removal efficiency was studied using two mass ratios of nZVI to heavy metal: 7–9:1 and 140–180:1. In the first case, the capacities of heavy metals removal were found to be 79.33–102.00 mg per g of nZVI for Cd, 111.11-142.85 mg per g of nZVI for Cu, 107.30–137.96 mg per g of nZVI for Ni, and 110.97–142.68 mg per g of nZVI for Pb. In this treatment, nanoparticles formed larger structures with heavy metals and they were easily removed from water by filtration. In the second case, the removal efficiencies of heavy metals were lower. There were more discrete nanoparticles that not formed larger structures and could not be easily filtered. In this treatment, the acidification of the filtered solutions caused the formation of deposits and subsequent re-dissolution of some heavy metals back to solutions.