Removal of heavy metal ions from aqueous solution using Fe3O4–SiO2-poly(1,2-diaminobenzene) core–shell sub-micron particles

[Display omitted] ► Fe3O4–SiO2-poly(1,2-diaminobenzene) core–shell sub-micron particles were prepared. ► They could effectively adsorb As(III), Cu(II), and Cr(III) from solutions. ► The data fitted well with Freundlich and two-site pseudo-second-order models. ► Their stability and magnetic recovery were beneficial for the application. In this work, Fe3O4–SiO2-poly(1,2-diaminobenzene) sub-micron particles (FSPs) with high saturated magnetization of ∼60–70emu/g were developed and utilized for the removal of As(III), Cu(II), and Cr(III) ions from aqueous solution. The isothermal results fitted well with the Freundlich model and the kinetic results fitted well with the two-site pseudo-second-order model, which indicated that multilayer adsorption of As(III), Cu(II), and Cr(III) ions on FSPs occurred at two sites with different energy of adsorption. The maximum adsorption capacities followed the order of As(III) (84±5mg/g, pH=6.0)>Cr(III) (77±3mg/g, pH=5.3)>Cu(II) (65±3mg/g, pH=6.0). And the chelating interaction was considered as the main adsorption mechanism. The as-prepared materials were chemically stable with low leaching of Fe (⩽1.7wt.%) and poly(1,2-diaminobenzene) (⩽4.9wt.%) in tap water, sea water, and acidic/basic solutions. These metal-loaded FSPs could be easily recovered from aqueous solutions using a permanent magnet within 20s. They could also be easily regenerated with acid. The present work indicates that the FSPs are promising for removal of heavy metal ions in field application.