Magnetic Fe3O4 @ silica–xanthan gum composites for aqueous removal and recovery of Pb2+

• Naturally occurring xanthan gum (XG) for preparation of Fe3O4@SiO2–XG composites.
• Magnetic switchable composites for property of convenient solid/liquid separation.
• Non-toxic XG immobilized on magnetic Fe3O4 particles through TEOS sol–gel reaction.
• XG adopted as active sites for adsorptive removal of Pb2+ from aqueous solution.
• The composites reutilized and Pb2+ reused in battery wastewater by 0.05 mol L−1 HCl.

A magnetic Fe3O4 @ silica–xanthan gum composite was easily fabricated as a hybrid adsorbent for the removal and recovery of aqueous Pb2+ heavy metal. The natural polymer xanthan gum (XG) was fixed on the surface of the magnetic Fe3O4 microspheres through a sol–gel process. The condensation of XG molecule provided active sites for the selective adsorption of Pb2+ ions from the aqueous solution, and because the composite is magnetically switchable, the process of solid–liquid separation was convenient. Scanning electronic microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectrometry, thermogravimetry, and BET surface area determination were utilized for the characterization of the composites. The factors affecting Pb2+ adsorption in a batch mode were studied including the contact time (30–150 min), the pH of the media (2–10), the adsorbent dosage (0.01–0.2 g/20 mL), and the temperature (303–320 K). The Pb2+ adsorption followed pseudo-second-order kinetics, and the maximum Pb2+ sorption capacity was 21.32 mg g−1 at 293 K, pH = 6, according to the Langmuir isotherm. The thermodynamic parameters, including the equilibrium constant (K0 = 9.848), the standard free energy change (ΔG0 = −5.774 kJ mol−1), the standard enthalpy change (ΔH0 = 6.133 kJ mol−1), and the standard entropy change (ΔS0 = 39.21 J mol−1 K−1) were discussed. The targeted Pb2+ could be recovered efficiently using 0.05 mol L−1 HCl. Finally, the Fe3O4 @ silica–XG composites were attmepted for removal of Pb2+ from battery industry wastewater.

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