Agglomeration of 10 nm amine-functionalized nano-magnetite does not hinder its efficiency as an environmental adsorbent.

Amine-functionalized magnetite (nFe3O4-NH2) of two different sizes, 10 nm and 250 nm, were compared as environmental adsorbents. They were synthesized by co-precipitation (10 nm-nFe3O4-NH2) and solvothermal (250 nm-nFe3O4-NH2) methods, respectively. The prepared amine-functionalized magnetite was characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, vibrating sample magnetometer, Fourier transform infrared spectroscopy, size distribution analysis and surface area analysis to compare the properties of different sizes of nFe3O4-NH2. Both nFe3O4-NH2 contained cubic Fe3O4 crystalline structure. The 250 nm-nFe3O4-NH2 exhibited higher magnetic saturation value than the 10 nm-nFe3O4-NH2, but both could be separated from an aqueous solution using an external magnet. The surface area and pore volume of the smaller-sized 10 nm-nFe3O4-NH2 was larger than that of 250 nm-nFe3O4-NH2, but stronger aggregation was observed in the 10 nm-nFe3O4-NH2. Batch adsorption of lead indicated that the 10 nm-nFe3O4-NH2 was a better adsorbent than the 250 nm-nFe3O4-NH2. The maximum adsorption capacity of lead for the 10 nm-nFe3O4-NH2 and the 250 nm-nFe3O4-NH2 were 74.48 mg g-1 and 54.54 mg g-1, respectively. The stronger aggregation of nanoparticles with a smaller particle size did not affect the superior performance of the 10 nm-nFe3O4-NH2 as an environmental adsorbent.