Nanoscale dispersing of zero-valent iron on CaCO3 and their significant synergistic effect in high performance removal of lead.

Rapid aggregation and deactivation of nanoscale zero-valent iron (nZVI) hinder its application in environmental remediation. In this work, micro-scale CaCO3 is used as a dispersive carrier of nZVI to create a novel composite, CaCO3-supported nZVI (nZVI@CaCO3), through simplified liquid-phase reduction strategy. The morphology analysis shows that CaCO3 exhibits a fagot-like structure, and Fe0 particles are well dispersed on CaCO3 with an average diameter of around 15 nm. The removal of Pb(II) from water by nZVI@CaCO3 is studied, and it is found that the removal capacity of lead is as high as 3828 mg/g, which is much greater than that by neat CaCO3 (2209 mg/g) and bare nZVI (1308 mg/g). Owing to the loading of Fe (50%) in nZVI@CaCO3, a significant synergistic effect is observed between CaCO3 and nZVI in high performance removal of lead. Furthermore, a possible removal mechanism is proposed from a comparative investigation on the surface valence state and nZVI@CaCO3 phase before and after absorption of Pb(II). Considering the advantages of improved dispersibility, easy preparation and remarkable performance, the as-prepared nZVI@CaCO3 has the potential to become a promising remediation material for Pb(II) polluted water.