Tannic acid modified Fe3O4 core–shell nanoparticles for adsorption of Pb2+ and Hg2+

Tannic acid (TA) film covered magnetic microspheres (Fe 3 O 4 @TA–Fe 3+ ) was synthesized and applied for removal of Pb 2+ and Hg 2+ from aqueous solution. The resulted Fe 3 O 4 @TA–Fe 3+ was characterized with thermo-gravimetric analysis, vibrating sample magnetometer, transmission electron microscope, and Fourier transform infrared spectra. The adsorption of pollutants was pH dependent because the complexation of TA with Fe 3+ was disassembled at low pH. The composites showed high maximum adsorption capacity for Pb 2+ up to 1115.3   mg/g and Hg 2+ to 279.4   mg/g. Furthermore, the Fe 3 O 4 @TA–Fe 3+ composites could be easily separated from the solution by a magnet after adsorption because of the excellent superparamagnetic property. Thermodynamics study indicated that the adsorption of Pb 2+ and Hg 2+ on Fe 3 O 4 @TA–Fe 3+ sorbents was spontaneous, chaotic degree decreasing and endothermic process. The present results warrant the promising application of magnetic Fe 3 O 4 @TA–Fe 3+ composites for removal of Pb 2+ and Hg 2+ from contaminated water, and this study is the first application of TA film in environmental remediation.