One-step hydrothermal preparation of N-doped carbon spheres from peanut hull for efficient removal of Cr(VI)

Carbon microspheres have attracted considerable interest in the field of heavy metal wastewater treatment. Herein, waste peanut hull derived N-doped spherical carbons (WPHSC) were successfully prepared by a one-step mild hydrothermal method. The obtained samples were characterized by XRD, SEM, FT-IR and XPS. The adsorption tests indicated that the WPHSC show excellent adsorption performance for Cr(VI) with the maximum adsorption capacity of 181.82 mg g(-1). While treating the real electroplating wastewater with a WPHSC dosage of 4 g L-1, the Cr concentration significantly decreased from 652.96 mg L-1 to 113.42 mg L-1. The adsorption mechanism attributes to the electrostatic attraction and redox reaction between Cr(VI) and WPHSC. Importantly, this method can be extended to other waste plant biomass, including sunflower seed hulls, walnut shell, coconut shell and corncob as carbon sources. The adsorption removal efficiencies of the obtained carbon spheres for 100 mg L-1 Cr(VI) are all over 99.5 % with low residual concentrations less than 0.5 mg L-1. This universal study expands the scope of renewable raw materials for preparing carbon spheres with great application potential in the field of chromium-containing wastewater treatment.