Kinetics of the thermal regeneration of spent activated carbon in a fluidized bed
Activated carbon loaded with phenol, and spent carbon from a gold adsorption plant, were regenerated in a steam-nitrogen atmosphere in a small batch fluidized bed. Samples were treated at constant temperatures ranging from 300 to 900 ° C for different periods of time, after which the loss in mass was determined. A kinetic model was found to yield reasonable predictions of this mass loss. It was assumed that pyrolysis of the adsorbate and active groups proceeded via a first order reaction, and was more pronounced during the initial stages of regeneration. The maximum level of pyrolysis increased with increasing temperature. Gasification of the base carbon and the char residue was assumed to be dependent on the surface area. As this was assumed to remain reasonably constant, the carbon-steam reaction was assumed to be zero order. The activation energy of the pyrolysis reaction was 29.8 and 34.3 kJ mol-1 for the carbon loaded with phenol and the eluted plant carbon respectively. Corresponding values for the gasification reaction were 77.3 and 76.9 kJ mol-1. Silver cyanide was used to determine the equilibrium adsorption capacities of the regenerated samples of carbon. It was found that the temperature rather than the duration of regeneration influenced the activity of the carbon. © 1988.