Preparation of a porous carbon material by hydrothermal activation of itaconic acid fermentation waste liquid and its efficient adsorption of Cr(VI)

Carbon microspheres were synthesized using itaconic acid fermentation waste liquid as the raw material by the hydrothermal method. The sequential porous adsorbent was prepared (by chemical activation) using carbon microspheres as a carbonaceous framework. The adsorbent was characterized by SEM, BET, Raman, XRD, XPS, and elemental analysis. Also, the adsorption performance of the adsorbent was tested using the batch adsorption method. The effects of several parameters such as pH, adsorbent dose, and concentration of Cr(VI) on the sorption of Cr(VI) were investigated. The results indicate that an outstanding adsorbent with a specific surface area of 1802.16 m2 g−1 and a maximum adsorption capacity for Cr(VI) of 270.14 mg g−1 has been acquired. According to the adsorption isotherm model, the kinetic model, and the intra-particle diffusion model, it was found that the adsorption process of Cr(VI) by the adsorbent conforms to the Freundlich model and the quasi-second-order kinetic model. The evaluation of the thermodynamic parameters (ΔH > 0, ΔS > 0, and ΔG < 0) revealed that the adsorption process was endothermic and spontaneous. The mechanistic studies showed that the adsorption of Cr(VI) likely involved electrostatic attraction and a redox reaction. After 5 cycles of repeated usage, the adsorbent maintains good adsorption stability to Cr(VI), favoring its practical application.