Adsorption of SO2 from flowing air by alkaline-oxide-containing activated carbons

Adsorption of SO₂ under dynamic conditions from an SO₂-air mixture at 298 and 573 K on alkaline-oxide-containing activated carbons has been studied. The adsorption capacity of these samples at 298 K was, in general, lower than that in the original activated carbons and mainly governed by their microporosity accessible to benzene. However, at 573 K, the alkaline-oxide-containing activated carbons adsorbed a greater amount of SO₂ than the original activated carbon, following the order Na ≥ K > Rb. At both adsorption temperatures, part of the SO₂ adsorbed formed H₂SO₄ and Me₂SO₄, where Me = Na, K or Rb. When the SO₂ adsorption was carried out at 573 K, this gas fixed additional oxygen complexes that evolved as CO₂ under heating up to 873 K in He flow, probably by reaction of SO₂ with carbon surface atoms of a basic nature that are not able to chemisorb oxygen from the air at the same conditions.