Feasible synthesis of hierarchical porous MgAl-borate LDHs functionalized Fe3O4@SiO2 magnetic microspheres with excellent adsorption performance toward congo red and Cr(VI) pollutants

Abstract

Novel magnetic microspheres with core-shell structure, Fe3O4@SiO2@MgAl-borate LDH had been fabricated by a facile hydrothermal approach, in which the borate anions intercalated layered double hydroxides (MgAl-borate LDHs) loaded on a SiO2-coated Fe3O4 magnetite core, forming a flower-like hierarchical porous structure constructed by the assembly of ultrathin nanosheets. This composite was characterized via XRD, SEM, TEM, FT-IR, XPS, TG-DSC and VSM. It possessed superparamagnetic property, large specific surface area, moderate pore volume and excellent chemical stability. Benefiting from this unique structure, it exhibited superb adsorption performance. Its maximum adsorption capacities were 158.98 mg g−1 for CR at 298 K with pH = 4 and 86.73 mg g−1 for Cr(VI) at 298 K with pH = 5, which were larger than most of other similar adsorbent. The adsorption reaction followed the Langmuir model as well as pseudo-second-order rate equation. The higher temperature was in favour of adsorption. The ionic strength showed little effect on the sorption Cr(VI). Furthermore, the possible formation mechanism of this composite and its adsorption mechanism were also proposed. Overall, this new composite is expected to be an excellent adsorbent for CR and Cr (VI) in wastewater due to its superior structural stability, high efficiency, good reusability, and easy collection by magnetic separation.