g-C3N4 modified magnetic Fe3O4 adsorbent: Preparation, characterization, and performance of Zn(II), Pb(II) and Cd(II) removal from aqueous solution

A novel magnetic carbon nitrogen adsorbent (Fe3O4&g-C3N4) was first prepared by one step method and applied to remove Zn(II), Pb(II) and Cd(II) from aqueous solution. Scanning electron microscope (SEM), transmission electron microscope (TEM), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric analyzer (TGA), X-Ray fluorescence (XRF) and vibrating sample magnetometer (VSM) were used to character Fe3O4&g-C3N4. The adsorption performance of Fe3O4&g-C3N4 was evaluated by batch experiments with different pH, contact time, initial concentration and ionic strength. Pseudo-second-order model and intraparticle diffusion mode can well describe the adsorption kinetics data. Isothermal adsorption data was best fitted by Freundlich model and the adsorption capacity were 45, 137 and 102 mg/g (initial concentration: 200 mg/L) for Zn(II), Pb(II) and Cd(II), respectively. The result of X-ray photoelectron spectroscopy (XPS) survey spectrum suggested that the formation of conjugation of Fe3O4&g-C3N4 with heavy metal ions is the main adsorption mechanism for heavy metal ions on Fe3O4&g-C3N4. Moreover, the metal ions adsorbed Fe3O4&g-C3N4 could be regenerated by EDTA and the adsorption capacity of regenerative Fe3O4&g-C3N4 could maintain 88.9% after five cycles. Therefore, the Fe3O4&g-C3N4 is a potential adsorbent for separating Zn(II), Pb(II) and Cd(II) from wastewater.