The suspensions were then mixed end over end in incubators at
25, 35, or 45 C for 24 h. After reaching adsorption equilibrium,
Fe3O4@SiO2–NH2 nanoparticles were magnetically separated from
the aqueous solution and the residual concentrations of metal ions
in the aliquot were determined by atomic absorption spectroscopy
(AAS) (Hitachi Z-8100, Japan)