Sulfidation and sulfation of ceria(111) and ceria(110) surfaces are studied with the help of density functional theory (DFT) calculations (PBE+U). Under reducing atmosphere, SO2 adsorption leads to the formation of stable surface sulfate species on the (110) surface and sulfides on the (111) surface. A mechanism for sulfur recovery from SO2 is presented where SO2 reacts with a surface sulfide to form a thiosulfite species. This thiosulfite species is subsequently reduced by an oxygen vacancy and desorbed as S2(g).