Application of graphitic carbon nitride for the removal of Pb(II) and aniline from aqueous solutions

Graphitic carbon nitride (g-C3N4) was synthesized from urea with a facile approach and was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The as-synthesized g-C3N4 was applied as sorbent to remove Pb(II) and aniline from aqueous solutions as a function of contact time, solid content, pH, ionic strength, temperature, and initial concentrations of Pb(II) and aniline. The results indicated that the sorption of Pb(II) was mainly dominated by outer-sphere surface complexation or ion exchange at pH<7.0, but by inner-sphere surface complexation at pH>7.0. The sorption of aniline was mainly attributed to electrostatic interaction at pH<5.0, whereas the π-π electron donor-acceptor (EDA) interaction was the predominant sorption mechanism at pH>5.0. The sorption isotherms of Pb(II) and aniline on g-C3N4 were well described by the Langmuir model. The thermodynamic parameters calculated from the temperature-dependent sorption isotherms indicated that the sorption of Pb(II) and aniline on g-C3N4 was endothermic and spontaneous processes. Moreover, g-C3N4 could be regenerated through the desorption of Pb(II) and aniline by using 1.0M HCl solution and alcohol, respectively, and no obvious decline of sorption capacity was found for the recycling results. All these results indicated that g-C3N4 was a promising material for the preconcentration of Pb(II) and aniline from aqueous solutions in real pollution management.