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

Abstract Tannic acid (TA) film covered magnetic microspheres (Fe3O4@TA–Fe3+) was synthesized and applied for removal of Pb2+and Hg2+ from aqueous solution. The resulted Fe3O4@TA–Fe3+ 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 Fe3+ was disassembled at low pH. The composites showed high maximum adsorption capacity for Pb2+ up to 1115.3 mg/g and Hg2+ to 279.4 mg/g. Furthermore, the Fe3O4@TA–Fe3+ 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 Pb2+ and Hg2+ on Fe3O4@TA–Fe3+ sorbents was spontaneous, chaotic degree decreasing and endothermic process. The present results warrant the promising application of magnetic Fe3O4@TA–Fe3+composites for removal of Pb2+ and Hg2+ from contaminated water, and this study is the first application of TA film in environmental remediation.