Preparation of Amino Modified Fe3O4@SiO2 Composite by One-Pot Co-condensation Method with Enhanced Adsorption Performance Towards Cr(VI)

A one-pot co-condensation method was used to prepare three kinds of silane coupling agents containing different amounts of N atom modified and SiO2 coated magnetic adsorbents Fe3O4@SiO2-xN (x=1, 2, 3). Here, 1N, 2N, and 3N represent 3-aminopropyltrimethoxysilane, N-beta (aminoethyl)-gamma-aminopropyltrimethoxysilane and 2-[2-(3-Trimethoxysilylpropylamino)ethylamino]ethylamine, respectively. Their physicochemical properties were comparatively characterized by XRD, SEM, N-2 adsorption-desorption, elemental analysis, FT-IR and zeta potential. The results showed that the modified composites present good spherical morphologies and higher isoelectric points, and their nitrogen contents show the trend of Fe3O4@SiO2-1N<Fe3O4@SiO2-2N<Fe3O4@SiO2-3N. The static adsorption experiments towards Cr(VI) showed that the corresponding maximum adsorption capacity decreases with increasing nitrogen content, namely Fe3O4@SiO2-1N (79.74 mg.g(-1))>Fe3O4@SiO2-2N (63.05 mg.g(-1))>Fe3O4@SiO2-3N (55.37 mg.g(-1), and the mechanism on this trend was also analyzed. The adsorption experiments on simulated wastewater showed that the Fe3O4@SiO2-1N can adsorb some kinds of heavy metal ions simultaneously, and can achieve magnetic separation within 30 s.