Overcoming calcium catalysis during the thermal reactivation of granular activated carbon: Part II. Variation of steam-curing reactivation parameters

Abstract

In order to overcome the deleterious effects of calcium catalysis during thermal reactivation, the authors have developed a methodology for first steam-curing spent GAC at 548–748 K, and then ramping the furnace temperature to 1023–1223 K while exposing the GAC to flowing N 2. In this article, the authors evaluated the influence of an array of parameters on the steam-curing plus ramped-temperature protocol that included curing time, curing temperature, ramped-to temperature and steam flow rate. Pore size distribution (PSD) measurements employed the density functional theory (DFT), and these revealed that the steam-curing time had the greatest influence on pore size distribution: increasing the steam-curing time from 15 to 60 min increased the <500 Å cumulative pore volume by ca. 10% and the 5.4 to 32 Å pore volume by ca. 12%. Several of the other process parameters exhibited only a slight effect on PSD. Furthermore, a spent GAC that first experienced the steam-curing and ramped-temperature protocol and then experienced acid washing had identical micropore volume as a spent GAC that first experienced acid washing and then experienced conventional reactivation. This confirmed that the steam-curing protocol overcame calcium catalysis and its destruction of microporosity.