Hierarchically porous carbon monolithic column for efficient methyl orange adsorption under flow conditions

Abstract

This work presents a nanocasting fabrication method for highly porous carbon monoliths and their performance in a continuous-flow adsorption process of methyl orange from aqueous solutions. The monoliths were obtained using sucrose as a carbon precursor and a silica scaffold with exceptionally large macropores of approximately 100 μm as a hard template. The materials were characterised by nitrogen adsorption, SEM, thermogravimetry, and FTIR spectroscopy. Highly porous carbon monoliths with good mechanical stability were obtained by using a three-step impregnation process. The monoliths were characterised by a large specific surface area of 1399 m²=g, a total pore volume of 6:1 cm³=g, and a three-modal pore size distribution. They showed excellent adsorption properties under flow conditions. Regardless of the flow rate and the initial methyl orange concentration, the sorption capacity was close to the equilibrium capacity determined in the batch process, i.e. approximately 450 mg/g. The experimental breakthrough curves were well described by both the Thomas and Yoon–Nelson models. The sorption capacity in the monolithic column was 35 times greater than that in the packed-bed column with commercial microporous carbon grains under the same flow conditions