Abstract:

The use of nanoscale zero-valent iron is a promising technology for in situ environment remediation. However, due to the extremely high reactivity, nanoscale zero-valent iron tends to agglomerate or is easily oxidized by air resulting in the reduction of their chemical reactivity. We present here a simple method for the synthesis of nanoscale zero-valent iron(mean particle size 82.4 nm) on the basis of chitosan as a stabilizer. This chitosan-stabilized nanoscale zero-valent iron show no changes in reduction activity on storage at room temperature in air for 2 months. The TGA curve demonstrated that after modification by chitosan nanoscale zero-valent iron had a good thermal stability below 340 ℃. The synthesized chitosan-stabilized nanoscale zero-valent iron was powerful in reducing Cr(Ⅵ) and batch experiments indicated that after exposure to air atmosphere over a 60 d period the chitosan nanoscale zero-valent iron still exhibit high reducing capacity. Due to the presence of the —NH₂ and —OH groups chitosan has a better ability to chelate Fe(Ⅲ) and can inhibit the formation of Fe(Ⅲ)-Cr(Ⅲ) precipitation which increases the rates of iron corrosion and reduction of Cr(Ⅵ). Due to the good stability against oxidation in air the chitosan-stabilized nanoscale zero-valent iron have the potential to become an effective agent for in situ environment remediation.

Key words: Chitosan, Nanoscale zero-valent iron, Reduction