Synthesis of Chitosan-stabilized Nanoscale Zero-valent Iron for Removal of Hexavalent Chromium from Surface Water

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 rim) 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 degrees C. 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 (M) 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.