It can be completely absorbed.

The alum factory gas refers to the SO2 and SO3 produced by the decomposition of alum (a salt), which is converted into sulfuric acid under the action of air. The scientific name of alum is "ferrous sulfate heptahydrate" and its chemical formula is FeSO4·7H2O1. The alum plant gas is highly acidic and corrosive, which is harmful to the human body and the environment. However, the caustic soda solution can completely absorb the alum plant gas.

Caustic soda solution is a strong alkali that can react with the sulfuric acid in the alum plant gas to generate corresponding salts and water, thereby neutralizing acidic pollutants. The chemical equation of the reaction is as follows: SO2+2NaOH→Na2SO3+H2O. The method of using caustic soda solution to absorb alum plant gas is to pass the alum plant gas through a washing tower or absorption tower containing caustic soda solution to fully contact it with the caustic soda solution. and react to purify the gas.