SO2 was adsorbed, oxidized, hydrated, and recovered continuously as aqueous H2SO4 at 30-100 degrees C on a poly(acrylonitrile)-based active carbon fiber (PAN-ACF-FE-300). SO2 of 1000 ppm in a model flue gas was removed completely for longer than 60 h at 30 and 50 degrees C by W/F = 5.0 x 10(-3) g min mL(-1) by supplying sufficient humidity of 10 and 20 vol %, respectively. The heat treatment of the ACF at 800 degrees C was found very effective to enhance the catalytic activity, the temperature appearing very best between 30 and 1000 degrees C. A pitch-based activated carbon fiber exhibited less activity than PAN-ACF.