Synthesis and characterization of activated carbon from sugar beet residue for the adsorption of hexavalent chromium in aqueous solutions

Abstract

A series of micro–mesoporous activated carbons (ACs) were prepared from sugar beet residue by a two-step method including KOH chemical activation and were used for Cr(VI) removal from aqueous solutions. Several characterization techniques, including SEM, TEM, N₂ adsorption, XRD, FTIR, and Raman spectroscopy, were used to determine the chemical and physical characteristics of the ACs, and the adsorption properties of the ACs were tested. The results indicated that the high specific surface area of the ACs reached 2002.9 m² g⁻¹, and the micropore surface area accounts for 85% of the total area. The optimal conditions for achieving the maximum Cr(VI) adsorption capacity of 163.7 mg g⁻¹ by the ACs were activation with a KOH/carbon ratio of 3.0, an initial Cr(VI) concentration of 400 mg L⁻¹, an adsorbent dose of 2.0 g L⁻¹ and pH of 4.5. Therefore, the ACs exhibit excellent adsorption performance for removing Cr(VI) from aqueous solutions. According to an investigation of the adsorption process, the adsorption isotherm is most consistent with the Langmuir isotherm model, and the adsorption kinetics were well described by the pseudo-second-order model.