Magnetic Fe 3 O 4 @ silica–xanthan gum composites for aqueous removal and recovery of Pb 2+

A magnetic Fe 3 O 4 @ silica–xanthan gum composite was easily fabricated as a hybrid adsorbent for the removal and recovery of aqueous Pb 2+ heavy metal. The natural polymer xanthan gum (XG) was fixed on the surface of the magnetic Fe 3 O 4 microspheres through a sol–gel process. The condensation of XG molecule provided active sites for the selective adsorption of Pb 2+ 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 Pb 2+ 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 Pb 2+ adsorption followed pseudo-second-order kinetics, and the maximum Pb 2+ 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 ( K 0 = 9.848), the standard free energy change (Δ G 0 = −5.774 kJ mol −1 ), the standard enthalpy change (Δ H 0 = 6.133 kJ mol −1 ), and the standard entropy change (Δ S 0 = 39.21 J mol −1 K −1 ) were discussed. The targeted Pb 2+ could be recovered efficiently using 0.05 mol L −1 HCl. Finally, the Fe 3 O 4 @ silica–XG composites were attmepted for removal of Pb 2+ from battery industry wastewater.