Surface mercapto engineered magnetic Fe 3O 4 nanoadsorbent for the removal of mercury from aqueous solutions

Abstract

In this study, mercapto-functionalized nano-Fe 3O 4 magnetic polymers (SH-Fe 3O 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 3O 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 Δ H θ , Δ S θ and Δ G θ suggested that the adsorption processes of Hg(II) onto the SH-Fe 3O 4-NMPs were endothermic and entropy favored in nature, with Δ H θ at 30.31 kJ mol −1, Δ S 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 3O 4-NMPs decreased when Cl − existed.