BACKGROUND: To extend the working pH range of electro-Fenton, activated carbon fibre cathode (ACF) supported nano-Fe-0 catalysts were prepared by electo-deposition and applied to treat a dye effluent in a neutral aqueous medium. The morphology of the Fe-0/ACF cathode was characterized by X-ray diffraction and scanning electron microscopy. The experimental conditions, such as the initial pH, dye concentration and current density of the degradation of the dye effluent were investigated. A pseudo-first-order model was used to simulate the experimental results. RESULTS: Compared with Fe2+ and Fe3+, the degradation of Orange II solution by an Fe-0/ACF cathode was shown to achieve much better results at neutral pH values. Additionally, the dissolved iron concentration in the solution was also evaluated. The results showed that 0.79 mg L-1 of total iron was present after 120 min reaction time at neutral pH, suggesting that the Fe-0/ACF cathode can be used for a long time and is reusable under neutral pH conditions. A complete description of the possible degradation mechanism in solution is provided. CONCLUSION: The high catalytic activity of this cathode is probably due to the efficient electrotransfer at the Fe-0/iron oxide interface. All this demonstrates that Fe-0/ACF is a good and promising cathode for the neutral electro-Fenton process. (C) 2010 Society of Chemical Industry