Oxidative degradation of 4-chlorophenol in aqueous solution at normal temperature and pressure by the bimetallic Al-Fe/O-2 was investigated. The proposed main mechanism, verified by the addition of methanol and benzoic acid as (OH)-O-center dot scavenger and the detection of para-hydroxybenzoic acid, involves the in situ generation of H2O2 by the electron transfer from ZVAl to O-2, and the Fenton reaction occurring within ZVI and H2O2. The effects of initial pH, concentration of 4-chlorophenol and ethylenediaminetetraacetic acid, Fe content and Al-Fe loading were investigated. The results showed that the bimetallic AlFe/O-2 process exhibited higher reactivity than ZVAI/O-2 and ZVI/O-2 process and the 50 mg L-1 of 4-CP could be completely degraded in 2 h with the 100:1 mass ratio of Al and Fe. EDTA significantly enhanced the degradation of 4-CP with the optimized 1:1 mass ratio of Al and Fe while its appropriate initial concentration needed to be optimized. The degradation pathway of 4-CP in Al-Fe/O-2 may only follow 4-chlorocatechol pathway, while it may contain hydroquinone pathway in Al-Fe/O-2 + EDTA. (C) 2013 Elsevier B.V. All rights reserved.