Abstract: Aqueous glyoxylic acid solution is used to absorb sulfur dioxide and sulfur trioxide from a gaseous stream and the absorbed sulfur dioxide being removed from the aqueous glyoxylic acid solution by stripping and the absorbed sulfur trioxide being thereafter removed from the stripped glyoxylic acid solution. In a preferred embodiment, the absorbed sulfur trioxide is removed from the stripped glyoxylic acid solution by precipitation as barium sulfate. Particularly, sulfuric acid or absorbed sulfur trioxide in aqueous glyoxylic acid solutions may be removed by contacting the aqueous glyoxylic acid solutions with a barium compound such as barium hydroxide which is substantially inert to the glyoxylic acid but which precipitates barium sulfate from the aqueous glyoxylic acid solution.

Abstract: Sulfuric acid or absorbed sulfur trioxide in aqueous glyoxylic acid solutions may be removed by contacting the aqueous glyoxylic acid solutions with a barium compound such as barium hydroxide which is substantially inert to the glyoxylic acid but which precipitates barium sulfate from the aqueous glyoxylic acid solution. In a preferred embodiment, aqueous glyoxylic acid solution is used to absorb sulfur dioxide and sulfur trioxide from industrial flue gases and the absorbed sulfur dioxide being removed from the aqueous glyoxylic acid solution by stripping and the absorbed sulfur trioxide being removed from the stripped glyoxylic acid solution by precipitation as barium sulfate.