An earlier study from our laboratory using nonaqueous solvents to increase the concentration of acid recovered from adsorbing and reacting SO2 to form SO3 on activated carbon is extended to additional organic solvents and the use of subcritical and supercritical. CO2. However, our conclusion from the previous work that organic solvents make suitable flushing agents is contradicted because of the degradation of some solvents or the discoloration of the acid product. Desorption Of SO3 from activated carbon using supercritical CO2, however, is satisfactory. A statistically designed study showed that the temperature, pressure, and superficial velocity of CO2 fed to the carbon bed control the recovery.