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

Abstract

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 (30–150min), the pH of the media (2–10), the adsorbent dosage (0.01–0.2g/20mL), and the temperature (303–320K). The Pb2+ adsorption followed pseudo-second-order kinetics, and the maximum Pb2+ sorption capacity was 21.32mgg−1 at 293K, pH=6, according to the Langmuir isotherm. The thermodynamic parameters, including the equilibrium constant (K0=9.848), the standard free energy change (ΔG0=−5.774kJmol−1), the standard enthalpy change (ΔH0=6.133kJmol−1), and the standard entropy change (ΔS0=39.21Jmol−1K−1) were discussed. The targeted Pb2+ could be recovered efficiently using 0.05molL−1 HCl. Finally, the Fe3O4 @ silica–XG composites were attmepted for removal of Pb2+ from battery industry wastewater.