Adsorption of SO2 on alumina

The adsorption of SO2 on alumina used in the aluminium industry, the so-called smelter-grade alumina, was studied in the temperature range 15-120 degrees C. It was found that at temperatures lower than 40 degrees C, sulphur dioxide was bonded to alumina reversibly by physical forces, and the adsorption could be described satisfactorily by the Langmuir adsorption isotherm. The heat of adsorption was estimated to be -33 kJ mol(-1). At temperatures ranging from 80 degrees C to 120 degrees C, which prevail in dry scrubbers in the aluminium industry, the heat of adsorption was determined to be -56 kJ mol(-1). When SO2 was adsorbed at temperatures higher than 80 degrees C, about 30 % of the SO2 could not be desorbed even if the samples were heated up to 250 degrees C. In the presence of SO2 and oxygen, the formation of sulphate was observed at temperatures above 90 degrees C.