Effect of iron and sulfur on thermal regeneration of GAC

Abstract

Iron accumulations on coal‐based GAC or wood‐based GAC had little or no catalytic influence on regeneration behavior during the first regeneration cycle. Regeneration of spent granular activated carbon (GAC) can be affected by inorganics that have accumulated by ion exchange on specific GAC sites, precipitation, or adsorption of metal‐organic complexes. The authors found iron (Fe) in several spent GAC samples. Sulfur (S) always appeared in these GAC samples as well. Although Fe catalyzes the gasification of GAC to oxides of carbon, Fe catalysis of GAC gasification experienced dramatic inhibition by S at concentrations as low as 100–300 mg S/kg GAC (0.01–0.03 percent). When S was reduced to 20 mg S/kg GAC, the Fe at 1 percent loading became a strong catalyst. Because S is usually present in spent GACs at concentrations that inhibit catalysis, thermal regenerations behaved essentially the same whether Fe was present or absent.

Perchlorate removal via IRON‐PRELOADED GAC and BOROHYDRIDE REGENERATION

“…The drying would diminish the waters of hydration within the iron complex, and it could also cause the loaded iron to become more ordered, less amorphous, lower in surface area, and lower in cationic surface charge. Moreover, the 105°C drying temperature could accelerate the rate at which Fe(III) could convert oxalic acid to carbon dioxide whereas the Fe(III) itself converts to Fe(II) (Cannon et al, 1997). In turn, the air from the drying protocol could convert Fe(II) to Fe(III) and also create iron oxides from either iron–oxalic acid complexes or iron hydroxides.…”

Deleterious effects of inorganic compounds DURING THERMAL REGENERATION OF GAC: A Review

“…In addition, the catalytic activity of Fe is inhibited by the S content of most commercial GAC materials and from H 2 S in the flue gases. Both FeS 2 and FeS are poor C‐gasification catalysts (Cannon et al, 1997; Walker et al, 1983; Attar, 1978;). Thus, Fe is not typically an important catalyst.…”

Enhancing Activated Carbon Adsorption of 2-Methylisoborneol: Methane and Steam Treatments

“…Since H 2S and COS are commonly released during coal gasification (32), there is a great potential for sulfur to poison catalytic sites within activated carbon. Cannon et al (33) similarly observed that sulfur poisoned the iron-catalyzed gasification of GACs during thermal reactivation. Finally, carbon deposition onto catalysts presents a problem similar to sulfur poisoning.…”