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

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.

Corn stalk-based activated carbon synthesized by a novel activation method for high-performance adsorption of hexavalent chromium in aqueous solutions.

A simple activation method involving treatment with KOH solution was used to synthesize activated carbon (ACs) with micro-meso pores from the agricultural waste of corn stalks. The activation reagent, KOH solution, was easily separated for recycling by centrifugation from the pre-treated corn stalks, and the pollution in the carbonization process was greatly reduced. The morphology and structure of the ACs were characterized by SEM, TEM, N2 adsorption, XRD, FT-IR and Raman analysis. The prepared carbon was applied as an adsorbent for the removal of Cr(VI) in a batch adsorption process. The effect of the concentration of KOH solution on the structure, morphology and Cr(VI) adsorption performance of the synthesized ACs was investigated. The characterization results revealed that some functional groups in the corn stalks were removed by pretreatment with KOH solution and micro-meso porous structures were generated. The ACs showed high adsorption performance for Cr(VI), and the maximum adsorption ability of the ACs prepared by activation with 4% KOH solution reached 89.5 mg g-1 at an adsorbent dosage of 2.5 g·L-1 and pH value of 4.5.