Synthesis and characterization of porous magnetic silica composite for the removal of heavy metals from aqueous solution

• Porous Fe3O4@nSiO2@mSiO2 has been synthesized and characterized.
• Adsorption of Pb(II) and Cd(II) in single and binary systems was studied.
• Adsorption process followed pseudo-second order kinetics and Langmuir isotherm.
• Adsorption of Pb(II) was 1.52 and 2.59 times higher than Cd(II) in single and binary system.

Magnetic core and porous silica shell (Fe3O4@nSiO2@mSiO2) composite has been synthesized using surfactant assisted template approach. The composite was characterized by scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy, Fourier transform-infrared spectroscopy. The efficiency of Fe3O4@nSiO2@mSiO2 for Pb(II) and Cd(II) adsorption was studied under the influence of solution pH, contact time and initial solution concentration. Kinetic study illustrated that the pseudo-second-order equation was well correlated with the kinetic data, and the intra-particle diffusion model indicated the multi step adsorption process. In single metal adsorption system, the adsorption affinity of Fe3O4@nSiO2@mSiO2 for Pb(II) was 1.52 times greater than Cd(II) while in binary system, it was 2.59 times higher at pH 5.5.

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