Adsorption of lead ions on magnetically separable Fe3O4 watermelon composite

Abstract

Abstract The search for green methods for the synthesis of eco-friendly and sustainable materials is the focus of many studies. In this paper, magnetite nanoparticles (WM-Fe3O4) were synthesized using watermelon rind as a stabilizing agent and their adsorption capacity for the removal of lead ions was evaluated. The synthesized WM-Fe3O4 was characterized using Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. Adsorption capacity and mechanism of WM-Fe3O4 for the removal of lead ions from water were evaluated. The adsorption isotherms data were well described by both Langmuir and Freundlich isotherms showing the heterogeneous nature of the adsorbent. Adsorption kinetics followed the pseudo-second-order model which confirmed the heterogeneity of the adsorbent and shows that adsorption followed chemisorption. Adsorption capacity was found to be 138 mg/g for lead. The initial solution pH had an influence on the adsorption. The removal efficiency decreased after pH 7. Effect of varying adsorbent mass indicates that a low dosage is required thereby favouring industrial scale up. The adsorption of lead ions was mainly controlled by electrostatic attraction and polar interactions. This adsorbent has potentials for the efficient capture of heavy metals with possibilities for the future replacement of expensive adsorbents.

Keywords

• Green synthesis
• Magnetite
• Watermelon rind
• Adsorption
• Sustainable
• Nanoparticles