Materials Chemistry and Physics, Vol.222, 369-376, 2019
Activated carbon supported nanoscale zero-valent iron composite: Aspects of surface structure and composition
Investigations relevant to the influences of AC support and conditions on the surface structure and composition were not reported previously. The present work synthesized a series of NZVI/AC composites using a liquid phase reduction method at a BH4- to Fe2+ molar ratio of 2:1, 4:1, 6:1, and 8:1 (designated as NZVI/AC-1, NZVI/AC-2, NZVI/AC-3, and NZVI/AC-4, respectively), which were subsequently characterized by various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. It was demonstrated that the amorphous NZVI partially doping with Fe3O4 was immobilized in NZVI/AC-1 sample. The surface structure of the NZVI/AC samples was divided into three types: needle-like shape, interconnected nanoparticles (similar to 30 nm) in or close to the pores of the AC support (self-assembling growth), and uniformly dispersed nanoparticles (20-30 nm) on the AC surface plane (individual NZVI nanospheres growth). Based on TEM images, NZVI particles found in or close to the pores of AC support were transformed from a needle-like shape to chain-like nanospheres as the molar ratio of BH4- to Fe2+ was increased from 2:1 to 8:1. Furthermore, the amount of Fe(OH)(3) in the surface oxides increased along with decline of gamma-FeOOH and other iron oxides as the molar ratio of BH4- to Fe2+ was increased. Meanwhile, Pb(II) removal tests indicated that NZVI/AC-4 sample afforded the highest Pb(II) removal efficiency. In summary, the small particle size and low extent of surface oxidation of AC-supported NZVI particles facilitate the intrinsic reactivity in decontaminations.