Alginate modified graphitic carbon nitride composite hydrogels for efficient removal of Pb(II), Ni(II) and Cu(II) from water.

The removal of heavy metal ions is of great significance to the friendly development of the environment. Herein, alginate modified graphitic carbon nitride composite hydrogels (g-C3N4/SA) were successfully synthesized through a facile cross-linking polymerization method. This novel composite hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS). The effects of different conditions were examined such as pH, initial concentration and contact time. It demonstrated that this integration process significantly improved the adsorption capacity of each component to targeted metal ions and solved the recycling and separation problem of g-C3N4, which is powdery sorbent and hard to recycle after adsorption. The calculated maximum adsorption capacity of Pb(II), Ni(II) and Cu(II) were 383.4, 306.3 and 168.2 mg g-1, respectively. Adsorption isotherms studies showed that the equilibrium adsorption data fitted well to the Langmuir model and the adsorption kinetic data described well with the pseudo-second-order model according to kinetics studies. More significantly, g-C3N4/SA showed excellent regeneration ability and repeatedly utilized at least five cycles without obvious adsorption capacity loss. As-fabricated g-C3N4/SA can be considered as a potential sorbent for highly effective adsorption of Pb(II), Ni(II) and Cu(II) ions from contaminated water.