Study on adsorptive behavior of pyrolytic nitrogen-doped graphene gel

Abstract A series of 3D nitrogen-doped graphene gels (NG) were synthesized by the hydrothermal process and further modified by pyrolysis. Characterization results indicated that the distribution of nitrogen- and oxygen-containing groups on the pyrolytic NG surface was significantly affected by the pyrolysis temperature. In the adsorption test, the NG adsorbent treated at 1000 °C showed the best performance for methylene blue. As the temperature increases from 200 to 1000 °C, the adsorptive capacity of pyrolytic NG hybrids was enhanced gradually, accompanied by the improvement of the adsorptive rate. Moreover, all NG adsorbents were fit for Langmuir isotherm. However, the adsorption dynamic behavior of pyrolytic NG hybrids followed pseudo-second-order model rather than pseudo-first-order model when the pyrolysis temperature exceeds 1000 °C. The above results are possibly attributed to the synergistic effect between specific surface area and the functional groups on the surface of adsorbents.