Amino-functionalized Fe3O4/SiO2 magnetic submicron composites and In3+ ion adsorption properties

Five kinds of amino-functionalized (polyaniline, poly(1,2-diaminobenzene), poly(1,3-diaminobenzene), poly(diphenylamine), and poly(o-toluidine)) Fe3O4/SiO2 submicron composites (SCs) were prepared. The SEM and TEM results showed that these SCs possessed a sphere-like core/shell structure with an average diameter of ~500 nm. The XRD results indicated good crystallinity of Fe3O4 core, the amorphous SiO2, and amino-functionalized shells. The XPS results confirmed that amino groups were plentiful rich outside the surface of these SCs which acted as the effective groups for adsorbing the metal ions. These SCs showed a good thermal stability at 20–250 °C. The high saturation magnetization of 60–70 emu/g is better than other similar reports. In3+ adsorption coefficients from aqueous solution by these SCs were higher than 106 mL/g, indicating the higher selectivity and affinity to In3+ compared with Cd2+ and Hg2+ ions. In addition, these SCs could be magnetically reclaimed within 30 s and regenerated with acid after adsorption. The adsorption capabilities only decreased by 6 % after five cycles. The present work indicates that the amino-functionalized Fe3O4/SiO2 SCs are promising for removal of In3+ ions in field application.