| Summary: | In this study, magnetic Fe<sub>3</sub>O<sub>4</sub> particles and Fe<sub>3</sub>O<sub>4</sub>-Ag<sup>0</sup> nanocomposites were prepared by a facile and green method, fully characterized and used for the removal of Hg<sup>2+</sup> from water. Characterizations showed that the Fe<sub>3</sub>O<sub>4</sub> particles are quasi-spherical with an average diameter of 217 nm and metallic silver nanoparticles formed on the surface with a size of 23–41 nm. The initial Hg<sup>2+</sup> removal rate was very fast followed by a slow increase and the maximum solid phase loading was 71.3 mg/g for the Fe<sub>3</sub>O<sub>4</sub>-Ag<sup>0</sup> and 28 mg/g for the bare Fe<sub>3</sub>O<sub>4</sub>. The removal mechanism is complex, involving Hg<sup>2+</sup> adsorption and reduction, Fe<sup>2+</sup> and Ag<sup>0</sup> oxidation accompanied with reactions of Cl<sup>−</sup> with Hg<sup>+</sup> and Ag<sup>+</sup>. The facile and green synthesis process, the fast kinetics and high removal capacity and the possibility of magnetic separation make Fe<sub>3</sub>O<sub>4</sub>-Ag<sup>0</sup> nanocomposites attractive materials for the removal of Hg<sup>2+</sup> from water.
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