Functional nanomaterials: Study on aqueous Hg(II) adsorption by magnetic Fe3O4@SiO2-SH nanoparticles

A selective adsorbent for Hg(II) was prepared by coating Fe 3 O 4 nanoparticles with SiO 2 which was further functionalized with thiol (–SH) group. The new adsorbent (Fe 3 O 4 @SiO 2 -SH) was shown to adsorb aqueous Hg(II) species in a wide range of pH (1.0–8.0) conditions. The Hg(II) adsorption capacity q e was more than 90.0 mg g −1 at pH > 3.0, and was slightly decreased to 84.6 mg g −1 under strong acidic conditions due to the electrostatic repulsion. The Langmuir isotherm model fitted the adsorption data better than the Freundlich, Temkin, and Dubinin-Radushkevich isotherms models. The maximum adsorption capacity of Fe 3 O 4 @SiO 2 -SH for Hg(II) was 132.0 mg g −1 . The adsorption kinetics were shown to follow the pseudo-second-order kinetic model, and the kinetic constant k 2 was 2.4 × 10 −3  g mg −1  min −1 . The magnetic retrieve of the newly-developed adsorbent was easily carried out via an external magnetic field, enabling both excellent adsorbent utilization and adsorption efficiency at high Hg(II) concentrations.