Advanced oxidant regeneration of granular activated carbon for controlling air-phase vocs

The Pennsylvania State University is researching an advanced oxidation (AO) system for controlling volatile organic compounds (VOCs) (Cannon et al. 1994). The system includes an air-phase photolytic chamber, an air/water stripping tower, and granular activated carbon (GAC) beds, and the work herein describes he evaluation of the GAC beds. Field GACs have been evaluated, which had previously beer, loaded with VOCs and regenerated with AO for several years at several full scale installations. Full scale response then was simulated in laboratory-scale experiments. Results revealed that following 500 to 1000 daily loading and regeneration cycles, one field GAC lost 35% of its micropore volume, and 17-35% of its capacity to adsorb several VOCs. Under another condition, for a furniture coating GAC, 80% of the micropore volume was lost after several years of loading and reactivation cycles, and 23 to 63% of the VOC adsorption capacity was lost.Laboratory results revealed that prolonged AO regeneration destroyed or desorbed most of the MBK within the first inch of a GAC bed. AO regeneration also removed a fourth of the MIBK in the next five inches of the packed GAC bed. Several byproducts were created by the MIBK destruction, which generally contained one-to-three fewer carbon atoms than does MIBK, and also contained more oxygen functional groups. Concurrent with these experiments, thermogravimetric analysis (TGA) tests were performed to evaluate the rate and extent of MIBK adsorption onto virgin GAC, and revealed that the MIBK adsorption capacity was fairly insensitive to the ranges of concentration and temperature that were employed. A modeling analysis of the diffusion characteristics onto virgin GAC revealed that during the time frame of three to five hours, the mass transfer rate appeared to be governed by restricted diffusion.