Pore structure and adsorption performance of the KOH-activated carbons prepared from corncob

摘要

Carbonaceous adsorbents with controllable surface area were chemically activated with KOH at 780 deg C from chars that were carbonized from corncobs at 450 deg C.The pore properties,including BET surface area,pore volume,pore size distribution,and mean pore diameter of these activated carbons,were characterized by the t-plot method based on N2 adsorption isotherms.Two groups are classified according to the types of adsorption/desorption isotherms.Group I corncob-derived activated carbons,with KOH/char ratios from 0.5 to 2,exhibited BET surface area ranging from 841 to 1221 m~2/g.Group II corncob-derived activated carbons,with KOH/char rations from 3 to 6,showed high BET surface areas,from 1976 to 2595 m~2/g.From scanning electron microscopic(SEM)results,the surface morphology of honeycombed holes on corncob-derived activated carbons was significantly influenced by the KOH/char ratios.The adsorption kinetics of methylene blue,basic brown 1,acid blue 74,2,4-dichlorophenol,4-chlorophenol,and phenol from water at 30 deg C were studied on the two groups of activated carbons,which were suitably described by two simplified kinetic models,pseudo-first-order and pseudo-second-order equations.The effective particle diffusivities of phenols and dyes at the corncob-derived activated carbons of group II are higher than those of ordinary activated carbons.The high-surface-area activated carbons were demonstrated to be promising adsorbents for pollution control and for other applications.