Enhanced adsorptive removal of Cr(III) from the complex solution by NTA-modified magnetic mesoporous microspheres

The Fe 3 O 4 @nSiO 2 @mSiO 2 /NTA (FNMs-NTA) was prepared by grafting magnetic mesoporous microspheres with nitrilotriacetic acid (NTA) and applied as an adsorbent for the removal of Cr(III) from complex solutions. Some characterization techniques including Brunauer–Emmett–Teller (BET), Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), small-angle X-ray diffraction (SAXS), vibrating sample magnetometer (VSM), and thermal gravimetric analysis (TGA) were used to characterize functional groups and pore structure of FNMs-NTA, which proved that NTA was successfully decorated onto the magnetic Fe 3 O 4 @nSiO 2 @mSiO 2 (FNMs) and FNMs-NTA featured a regular mesoporous structure. The batch adsorption of Cr(III) by FNMs-NTA exhibited high adsorption capacity (16.0 mg·g −1 at pH 3.0, and 25 °C). Adsorption data followed Freundlich isotherm and adsorption process was a spontaneous adsorption process. Moreover, the kinetics of adsorption were well explained by pseudo-second-order kinetic model. FNMs-NTA showed resistance to interfering inorganic cations (Na + , Ca 2+ ) and complexing agents (EDTA). Furthermore, FNMs-NTA exhibited remarkable regeneration performance and easy separation under external magnetic field. X-ray photoelectron spectroscopy (XPS) analysis showed the FNMs-NTA had excellent adsorption ability for Cr(III) because of the ion exchange and surface complexation.