Journal of Materials Research

Articles—Energy and The Environment Special Section

Nanoporous zero-valent iron

Jiasheng Caoa1, Patrick Clasena1 and Wei-xian Zhanga1 c1

a1 Center for Advanced Materials and Nanotechnology, Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, Pennsylvania 18015


Hollow and nanoporous particles of zero-valent iron (ZVI) were prepared with template-directed synthesis. Polymer resin beads (0.4 mm diameter) were coated with nanoscale iron particles by reductive precipitation of ferrous iron [Fe(II)] with sodium borohydride. The resin was calcinated at 400 °C to produce hollow and nanoporous iron spheres. The nanoporous iron oxides were then reduced to metallic iron by hydrogen at 500 °C. Scanning electron microscope images of the reduced iron spheres showed that the particles were hollow. The shell thickness was approximately 5 μm and highly porous. Brunauer–Emmett–Teller specific surface area was 2100 m2/kg. In comparison, the theoretical specific surface area of solid iron particles of the same size is just 1.9 m2/kg. Batch tests showed that the surface area normalized reactivity of the porous particles were 14–31% higher than microscale iron particles with similar surface areas for the transformation of hexavalent chromium [Cr(VI)], azo dye Orange II {4-[(2-hydroxyl-1-naphthalenyl)azo]-benzenesulfonic acid monosodium}, and trichloroethene. The combined performance enhancement (larger surface area and higher surface activity) is significant (>1200 times).

(Received April 21 2005)

(Accepted July 14 2005)

(Online publication December 2005)

Key Words:

  • Chemical reactivity;
  • Metal;
  • Porosity


c1 Address all correspondence to this author. e-mail: