Thermal regeneration of activated carbon saturated with p-nitrophenol

Water contamination by organic compounds is an important environmental problem. Activated carbon filters are widely used to eliminate these contaminants. After exhaustion, activated carbon must be regenerated or replaced by fresh carbon. In this study thermal regeneration of saturated carbon with p-nitrophenol has been analysed. Three thermal regeneration methods have been tested: (1) pyrolysis, (2) pyrolyis-gasification and (3) direct gasification, the gasifying agents being air and CO2. The results show that the pyrolysis treatment does not completely eliminate the contaminant from the carbon and the recovery of the initial adsorption properties is rather limited. The effect of gasification depends on both the gasifying agent and the sample (pyrolysed or saturated with PNP). CO2 -gasification yields to a complete regeneration of the adsorption characteristics in both pyrolysis-gasification and direct gasification samples. In general, air-gasification produces lower regeneration properties, although direct air-gasification sample has 87% recovery of the PNP maximum adsorption capacity. These results suggest that thermal regeneration could be carried out in a single step, simplifying the process and reducing the operation cost. Moreover, although CO2 seems to give better recovery of the initial carbon characteristics than air, it should be noted that air is cheaper and the regeneration time is shorter. (C) 2004 Elsevier Ltd. All rights reserved.