Preparation of nitrogen-doped porous carbon material by a hydrothermal-activation two-step method and its high-efficiency adsorption of Cr(VI).

Nitrogen-doped carbon spheres (CSs-N) were synthesized by a hydrothermal method with glucose as the carbon source and urea as the nitrogen source. The synthesized nitrogen-doped carbon spheres were activated by KOH to prepare high performance nitrogen-doped porous carbon material (PCM-N) for adsorption of Cr(VI). SEM, TEM, BET, Raman spectroscopy, XRD, XPS, Zeta potential and elemental analysis techniques were used to characterize the materials, and the properties of the materials were tested by a batch adsorption method. The results show that the specific surface area of PCM-N is 1600.67 m2/g, and the maximum adsorption capacity of Cr(VI) is 402.9 mg/g, and the performance was better than that of a similar materials (Longan seed and Fox nutshell and so on). Furthermore, the adsorption capacity will increase with increasing temperature. In this study, the kinetics and isotherm model of adsorption parameters are fitted, and it is found that the adsorption process is in accordance with the Pseudo-second-order kinetic model and Freundlich model, thermodynamic parameters show that the adsorption of Cr(VI) onto the PCM-N was spontaneous endothermic process. The regeneration adsorption experiment showed that PCM-N has good reusability and high application value.