Overcoming calcium catalysis during the thermal reactivation of granular activated carbon: Part I. Steam-curing plus ramped-temperature N2 treatment Original Research Article

Tailored thermal reactivations overcame calcium catalysis by first steam-curing spent GAG at 648 K for 60 min, and then thermally treating it in nitrogen under temperatures that ramped up to 1123 K, while some H2O remained temporarily sorbed within the GAC pores and the furnace enclosure. Pore volume distribution measurements using the density functional theory (DFT) software package revealed that this strategy increased the pore volume between 5.4 and 32 Å when compared to that of its virgin counterpart, or when compared to those of spent GAGs that were conventionally reactivated. The 5.4–32 Å pore range is important in terms of removing small organics from drinking water. These particular widths also represented convenient demarcations from our argon adsorption experimental protocol. The steam-curing plus ramped-temperature approach also achieved the same micropore volume (width <20 Å) as that found in the virgin GAC, and also more pores between 5.4 and 100 Å in width, when compared to its virgin counterpart. Pores between 5.4 and 100 Å cover an important range for removing the full molecular size distribution of organics that enter a GAC bed during drinking water treatment.