Thermal regenerations were conducted on a spent granular activated carbon (GAC) that had served in a water treatment plant for about four years and contained 1.8% calcium. Oxidation was conducted in steam, CO2, or steam plus CO2, at 650-950°C. As described earlier, when steam and CO2 were employed together, the regenerated product's pore structure maintained greater micropore volume at high temperatures ( > 800°C) than at low temperatures (<750°C). The work herein has linked this distinction to differences in reaction rate limitations: at high temperatures, with both oxidants employed together, the water-gas shift reaction (H2O + CO = H2 + CO2) limited overall rate, whereas at low temperatures, the C(O) gasification step limited overall rate. The CO2 created via the water gas shift reaction served as the primary oxidant. Although steam served only as a secondary oxidant, its presence also facilitated more extensive oxidant transfer to the carbon surface.
All Science Journal Classification (ASJC) codes
- Materials Science(all)