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

A selective adsorbent for Hg(II) was prepared by coating Fe3O4 nanoparticles with SiO2 which was further functionalized with thiol (-SH) group. The new adsorbent (Fe3O4@SiO2-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 Fe3O4@SiO2-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 x 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. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.