Electropolymerization biocarriers were prepared by the electropolymerization of polypyrrole (PPy) on an active carbon felt (ACF) electrode using doping anions anthraquinone-2-sulfonate (AQS) or Na2SO4. The functional electropolymerization biocarrier (ACF/PPy/AQS) with AQS was used as an immobilized redox mediator for the denitrification process. The characteristics of the electropolymerization biocarriers were analyzed by scanning electron microscope, elemental analyses, Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The results suggested that the denitrification efficiency increased nearly 1.5-fold with ACF/PPy/AQS (0.04 mmol L-1 AQS) compared to the control. A linear correlation was found for the k value and the AQS concentration (C-AQS), which was k = 624.71C(AQS) + 83.87 (R-2=0.9893). The ORP value stabilized around -200 mV for the denitrification process with ACF/PPy/AQS, which was -25 mV lower than that with ACF/PPy/Na2SO4. Repeated-batch operations indicated that the denitrification efficiency with ACF/PPy/AQS maintained over 90% of the original value and exhibited better catalytic activity and durability. (C) 2011 Elsevier Ltd. All rights reserved.