The electrochemical degradation of acid red B (ARB) using high surface area activated carbon fiber (ACF) as an anode or a cathode was investigated separately. In both systems, ARB could be thoroughly degraded and complete decoloration achieved. However, the mineralization rate of ACF cathode system was much higher than the other. 70% TOC removal was achieved in the ACF cathode system, while only 30% TOC was removed in the ACF anode system. The degradation process was analyzed and the reactive radicals were detected with the electron spin resonance technique. The results show that a high concentration of active hydroxyl radicals was produced in both systems, but the hydroxyl radical concentration in the ACF cathode system was much higher than that in the ACF cathode system. In the ACF cathode system, the electro-Fenton reaction occurred to generate a good many of hydroxyl radicals, which oxidized ARB much effectively. The effects of the current intensity and initial pH on both systems were also explored and the possible mechanisms were discussed.

Key words: activated carbon fiber, cathode system, anode system, electro-Fenton reaction, hydroxyl radical, acid red B