Self-templated synthesis of bifunctional Fe3O4@MgSiO3 magnetic sub-microspheres for toxic metal ions removal

Bifunctional Fe3O4@MgSiO3 sub-microspheres with superparamagnetic property and high affinity toward metal ions were successfully synthesized via a solvothermal method using Fe3O4@SiO2 as a self-template, and well characterized by means of TEM, XRD, FT-IR, VSM and N2 adsorption isotherms. The as-prepared Fe3O4@MgSiO3 sub-microspheres were then assessed as the adsorbent for Pb2+ removal in water, and various factors influencing the adsorption of Pb2+ were investigated including pH, equilibrium time and initial metal ion concentration. The results indicated that Fe3O4@MgSiO3 sub-microspheres had a mean diameter of 220 nm and high superparamagnetic cores, which endowed them with useful magnetic responsivity. Moreover, the large specific surface was beneficial for their strong affinity toward toxic metal ions. The pseudo-second-order equation could describe well the adsorption kinetics with correlation coefficients greater than 0.999. The maximum adsorption capacity for Pb2+ was calculated to be 242.1 mg/g based on Langmuir model. Furthermore, the as-prepared Fe3O4@MgSiO3 showed an acceptable reusability using NaOH or Mg2+ solution as the desorbing agent. All information gives an indication that the as-prepared sub-microspheres show their potential as the adsorbent for highly efficient removal of heavy metal ions in wastewater.

► Fe3O4@MgSiO3 is in situ prepared by etching Fe3O4@SiO2 with NaOH solution.
► The material has high adsorption capacity for heavy metal ion especially Pb2+.
► Fe3O4@MgSiO3 has good reusability using NaOH or Mg2+ as the desorbing solution.
► The adsorbent has great potential for removal of heavy metal ion in wastewater.