Elimination of 4-chlorophenol in aqueous solution by the bimetallic Al–Fe/O2 at normal temperature and pressure

• The Al–Fe/O2 process exhibited higher removal efficiency of 4-CP.
• The degradation pathway of 4-CP in Al–Fe/O2 may only follow 4-chlorocatechol pathway.
• Fenton reaction occurred within Fe and H2O2 generated by the reaction of Al and O2.
• EDTA significantly enhanced the degradation of 4-CP.
• The degradation pathway of 4-CP may contain hydroquinone pathway in Al–Fe/O2 + EDTA.

Oxidative degradation of 4-chlorophenol in aqueous solution at normal temperature and pressure by the bimetallic Al–Fe/O2 was investigated. The proposed main mechanism, verified by the addition of methanol and benzoic acid as OH scavenger and the detection of para-hydroxybenzoic acid, involves the in situ generation of H2O2 by the electron transfer from ZVAl to O2, and the Fenton reaction occurring within ZVI and H2O2. The effects of initial pH, concentration of 4-chlorophenol and ethylenediaminetetraacetic acid, Fe0 content and Al–Fe loading were investigated. The results showed that the bimetallic Al–Fe/O2 process exhibited higher reactivity than ZVAl/O2 and ZVI/O2 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/O2 may only follow 4-chlorocatechol pathway, while it may contain hydroquinone pathway in Al–Fe/O2 + EDTA.