NOVELTY - Absorption liquid containing ionic liquid is supplied to upper portion of absorption tower (13). Mixed gas (DD) containing acidic gas (BB) and non-acidic gas (AA) is supplied to lower portion of absorption tower. Acidic gas is absorbed to absorption liquid, and non-acidic gas and acidic gas are separated. The resulting absorption liquid is supplied to upper portion of regeneration tower (16). Acidic gas is diffused, and absorption liquid is recovered from regeneration tower and supplied to upper portion of absorption tower.    USE - For purifying gas, such as waste gas ejected from thermal power station, cement plant, steel plant and chemical processing plant, and separating hydrogen used for fuel cell mounted on motor vehicle.    ADVANTAGE - The acidic gas and non-acidic gas are efficiently and economically separated and recovered. The purified acidic gas is simply obtained and used for food additive.    DETAILED DESCRIPTION - Absorption liquid containing ionic liquid is supplied to upper portion of absorption tower (13) maintained at predetermined temperature and pressure. Mixed gas (DD) containing acidic gas (BB) and non-acidic gas (AA) is supplied to lower portion of absorption tower. The mixed gas is contacted with absorption liquid, acidic gas is absorbed to absorption liquid, and non-acidic gas and acidic gas are separated. The non-acidic gas is recovered from absorption tower. The resulting absorption liquid is supplied to upper portion of regeneration tower (16) maintained at temperature same or more than temperature of absorption tower, and pressure same or less than pressure of absorption tower. The acidic gas is diffused, and absorption liquid is separated and recovered from regeneration tower. The absorption liquid is regenerated. The regenerated absorption liquid is supplied to upper portion of absorption tower.    INDEPENDENT CLAIMS are included for the following:    (1) refiner of gas; and    (2) acidic gas absorbing liquid.    DESCRIPTION OF DRAWING(S) - The figure shows the cross-sectional view of purification apparatus of gas.    Dehumidifier (11)    Absorption tower (13)    Regeneration tower (16)    Circulation pump (17)    Non-acidic gas (AA)    Acidic gas (BB)    Gas mixture (DD)