Liquid-phase adsorption of phenol by activated carbons prepared from bituminous coals with different oxygen contents

Activated carbons prepared from two bituminous coals were used to adsorb ph enol in aqueous solutions. The major difference between the coal precursors is the oxygen content. The carbon preparation consisted of carbonization o f the coals followed by activation in CO2 to various extents of burn-off. E xperimental results show that the amount of phenol adsorbed generally incre ases with the BET surface area of the carbon. The carbons prepared from the coal with a higher oxygen content have larger surface areas, and, therefor e, exhibit higher capacities for phenol. The surface area of the carbon inc reases with the extent of carbon burn-off, whereas the increase in the adso rptive capacity due to the increasing burn-off level does not show a linear relationship with the increase in area; the ratio of the capacity to BET s urface area is not constant and decreases with the burn-off level. This has been attributed to the accessibility of phenol to the surface being affect ed by the length of diffusion path, which is an increasing function of the burn-off level or the particle size. The amount of phenol adsorbed decrease s with the temperature for these carbons. It was found, according to the La ngmuir model, that the adsorption process was significantly affected by the oxygen content in the coal precursors. (C) 1999 Society of Chemical Indust ry.