Spherical activated carbons for low concentration toluene adsorption

The activation process of a spherical activated carbon (SAC) from Kureha Carbon was analysed and the behaviour of these materials to adsorb low concentration volatile organic compounds was studied. Two series of activated carbons were prepared using CO2 or steam as activating atmospheres at 880 and 840 °C, respectively. Activation times between 45 min and 24 h were selected, leading to burn-offs between 21 and 60%. The results show, for similar burn-off percentages, that the porosity development is similar for the two activating gases at moderate burn-off percentages, and larger for CO2 than for steam at high burn-off percentages. For similar burn-offs, steam leads to SACs with slightly larger bed densities than CO2. In general, a low and similar increase in the total surface oxygen groups’ content is noted after activation with both activating agents. Toluene adsorption capacities as large as 46 g toluene/100 g SAC can be achieved with some of these spherical activated carbons in a continuous flow-through SAC bed, when influent air-phase toluene was 200 ppmv. Considering that these SACs have quite high bed densities, their toluene adsorption capacities per unit of volume reach remarkably high values.