Adsorptive Removal of Arsenic from Aqueous Solutions Using Magnetite Nanoparticles and Silica-Coated Magnetite Nanoparticles

Magnetite nanosorbents are known with high sorption capacity and ease of solid phase separation from surrounding liquid by the imposed external magnetic field. In this study, magnetite nanoparticles (MNPs) and silica-coated magnetite nanoparticles (Si-MNPs) were prepared and used for the removal of arsenic (III) from aqueous solutions. The nanosorbents were characterized by transmission electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. The spherical Fe3O4 nanoparticles in diameter of about 100 nm and SiO2 shells of 12 nm were formed. The saturation magnetization was found to be 78 and 58 e mug(-1) for MNPs and Si-MNPs, respectively. Under optimal conditions, both nanosorbents were very efficient for arsenite uptake (removal efficiency >= 99%). The highest removal percentage was obtained near PZC of nanosorbents where the net surface charge was zero. The MNPs exhibited higher sorption capacities in comparison with Si-MNPs although they tended to be agglomerated in higher applied doses. The kinetic of experiments indicated the best fit to the pseudo-second order model. Furthermore, the experimental data were best described by the Langmuir model. This study demonstrated the effectiveness of bare and silica coated magnetic nanoparticles to remove trace concentrations of arsenic (III) in water environment. (C) 2017 American Institute of Chemical Engineers