Abstract: Fe3O4 magnetic nanoparticles were first prepared using the coprecipitation method and were coated by SiO2. Functional magnetic nanometer materials were then obtained through bonding polyethylenimine(PEI) on the surface of SiO2 and quaternarization with benzyl chloride. Coating of SiO2 could increase the dispersion and stability of Fe3O4 nanometer materials. FT-IR, SEM, TG and vibrating sample magnetometer were used to characterize the magnetic nanomaterials. The results showed that the synthesis of magnetic nanomaterials was successful. The static adsorption method was employed to study the adsorption properties of magnetic nanomaterials towards Cr2O2-7 and various factors which might influence the adsorption performance of the materials. The optimal conditions for the separation and enrichment environment of heavy chrome acid radical are:acid medium, the temperature is 25 ℃, potassium dichromate concentration is 0.8 g/L, the adsorption quantity for 120 mg/g, grafting, the greater the amount of adsorption quantity increase.

Key words: magnetic nanomaterials, silica, polyethyleneimine, dispersion, stability