Synthesis and characterization of the sea urchin-like γ-AlOOH/Fe3O4@SiO2 nanosorbent with ultra-high performance of Congo red removal

Abstract

To manifest the benefits of nanosorbents in microstructure, the strong magnetism of Fe3O4 nanospheres is fully utilized to realize the rapid solid–liquid separation of adsorbent and aqueous solution. A sea urchin-like magnetic composite nanosorbent with a hierarchical structure was successfully manufactured by a simple and efficient liquid-phase hydrothermal synthesis method. Furthermore, its graded structure can sufficiently enhance the porosity and Zeta potential value of the material to increase the adsorption site and adsorption force between the material and CR molecular. The synthesized nanosorbent was then explored by a series of material physical and chemical characterization tools. It can be illustrated that the adsorbent is a strong magnetic composite nanomaterial with uniform particle size distribution and high dispersion, and is based on Fe3O4@SiO2 smooth nanoparticles as the inner core and γ-AlOOH as the shell. The saturation adsorption capacity reached 4534.57 mg g−1 with due expedition (under the adsorbent mass of 50 mg, CR mass concentration of 1500 mg/L, temperature of 25 °C and solution pH value of 3), whereas the γ-AlOOH of 925.34 mg g−1, Fe3O4 of 41.25 mg g−1 and Fe3O4@SiO2 of 93.21 mg g−1. After eight cycles of adsorption tests, the saturation capacity could still maintain 94.46% of the original adsorption capacity. Moreover, the adsorbent could be recovered by a simple applied magnetic field and the whole adsorption process conforms to the Pseudo-second kinetic model and the Langmuir isotherm model. Therefore, the sea urchin-like magnetic composite nanomaterials with a graded structure synthesized in this study could be widely utilized as a potential adsorbent material for CR removal.