Surface mercapto engineered magnetic Fe3O4 nanoadsorbent for the removal of mercury from aqueous solutions

In this study, mercapto-functionalized nano-Fe(3)O(4) magnetic polymers (SH-Fe(3)O(4)-NMPs) have been prepared and characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), thermogravimetry and differential thermogravimetry analyses (TG-DTA), as well as Fourier-transformed infrared spectroscopy (FTIR). The adsorptive characteristics of the SH-Fe(3)O(4)-NMPs intended for removal of mercury (II) were deeply studied. The results showed that the adsorption efficiency increased with pH increasing and reached a plateau at pH above 3.0. The adsorption data obtained at the optimized condition, i.e., 308 K and pH of 3.0, were well fitted with the Freundlich isotherm. The adsorption of Hg(II) reached equilibrium within 60 min. Thermodynamic parameters such as ΔH(θ), ΔS(θ) and ΔG(θ) suggested that the adsorption processes of Hg(II) onto the SH-Fe(3)O(4)-NMPs were endothermic and entropy favored in nature, with ΔH(θ) at 30.31 kJ mol(-1), ΔS(θ) at 111.41 J mol(-1) K(-1). The effects of mercury salts, i.e., Hg(NO(3))(2), HgSO(4), and different acids, were also deeply investigated and showed that the adsorption capacity of Hg(II) onto the SH-Fe(3)O(4)-NMPs decreased when Cl(-) existed.