Influence of a thin aluminum hydroxide coating layer on the suspension stability and reductive reactivity of nanoscale zero-valent iron

A novel structured material, aluminum hydroxide coated nanoscale zero-valent iron (NZVI@Al(OH)(3)), was synthesized to improve the applicability of NZVI in environmental remediation. Using a rate-control precipitation method, the surface of NZVI was covered with a thin shell of amorphous Al(OH)(3). 1-potential of NZVI under a weak alkaline condition became positive after coating with the Al(OH)(3) shell. NZVI@Al(OH)(3) performed remarkably higher suspension stability in aqueous phase than bare NZVI, owing to the increased electrostatic repulsion and the reduction of magnetic attraction between the NZVI@Al(OH)(3) particles. Results of H-2 generation test indicated that the pH buffering capacity of the Al(OH)(3) shell and the enlarged surface area benefitted the reductive reactivity of NZVI@Al(OH)(3). Additionally, the adsorption capability of the positive Al(OH)(3) shell facilitated the reduction and detoxification of contaminants on the NZVI surface. Consequently, the core-shell structure dependent modification with a thin inorganic shell with multiple functions is a promising design for environmental nanomaterials, and the NZVI@Al(OH)(3) synthesized in this study is a feasible and environmentally benign material for environmental remediation.