The degradation of 4-nitrophenol by electro-Fenton (E-Fenton) method was carried out in batch recirculation mode. The effect of operating conditions such as electrical current, Fenton's reagent dosage, Fe(II) to H2O2 molar ratio, and H2O2 feeding time on the efficiency of E-Fenton process was investigated. It was found that E-Fenton method showed the synergetic effect on COD removal. The increase of Fenton's reagent dosage, Fe(II) to H2O2 molar ratio, and the electrical current would lead to the increase of COD removal efficiency. Continuous addition of hydrogen peroxide was more effective than the addition of hydrogen peroxide in a single step and there existed an optimal H2O2 feeding time for COD removal. The reaction system was modeled as a plug flow reactor (PFR) in series with a continuous stirred tank reactor (CSTR), and the pseudo-first order rate constant of COD removal was determined from the model based on the experimental data. (c) 2006 Elsevier B.V. All rights reserved.