Preparation and properties of mesoporous activated carbons from NaOH-pretreated corncob residues

ObjectiveCompared with common activated carbon, mesoporous activated carbon has the advantages of good hydrophobic, large pore volume and high conductivity, etc. However, the traditional preparation method is complicated and has higher costs for raw materials. Therefore, it is crucial to explore new mesoporous activated carbon preparation method.

MethodActivated carbon with high mesoporous rate was prepared from corncob residues by NaOH pretreatment, followed by phosphoric acid activation. The influences of NaOH-pretreated time, ratio of H₃PO₄/corncob residues (impregnation ratio) and activation temperature on MB adsorptive property of the activated carbon were investigated through the single factor experiments.

ResultResults indicated that lignin removal from corncob residues by NaOH pretreatment may form pore gallery and swell the fibers, making it easier to contact with activator. As a consequence, activate carbon with high specific surface area and mesoporous rate was obtained. The best MB adsorption value of 436mg/g was achieved when corncob was pretreated by NaOH for 4 hours under a impregnation ratio of 4:1, activation temperature at 500℃ and activation time for 1 hour. Scanning electron microscopy (SEM) analysis showed that the surface of activated carbon was rich in mesopores and macropores. The developed pore structure and specific surface area were analyzed by N₂ adsorption tests. The surface area, total pore volume and average pore size of activated carbon were 2038m²/g, 2.13cm³/g and 4.18nm, respectively. Particularly, the mesoporous volume was 1.56cm³/g and the mesoporous rate was 73.2%.

ConclusionThe above mentioned results indicated that appropriate NaOH pretreatment contributes to the preparation of activated carbon with well-developed mesoporous structure, which has potential application in fields of heavy metal ion adsorption, organic macromolecular wastewater treatment and electronic components preparation, etc. Our work will provide a fundamental research for the efficient preparation of mesoporous activated carbon and promote the high-value utilization of the corncob residues.