EDTA enhanced degradation of 4-bromophenol by Al0–Fe0–O2 system

• The EDTA enhanced bimetallic Al–Fe–O2 process exhibited high removal efficiency of 4-BP.
• EDTA could be degraded simultaneously.
• Initial EDTA concentration needs to be optimized.
• It would not cause new metal pollution in effluent when ZVI is excess.
• Reactive oxygen species was in situ generated in this novel process.

An EDTA enhanced bimetallic Al0–Fe0/O2 process was proposed for spontaneous in situ production of H2O2 and OH to rapidly oxidize 4-bromophenol. The effects of EDTA on Al0/O2, Fe0/O2 and Al0–Fe0/O2 system were investigated. The mass ratio of Al0 and Fe0 was also optimized. The role of EDTA enhanced in situ production of OH was verified by the addition of methanol and benzoic acid as OH scavenger and the detection of para-hydroxybenzoic acid. Moreover, the degradation pathway of 4-bromophenol in Al0–Fe0/O2 system was analyzed by the verification of reaction intermediates and Br− concentration. And the robustness of EDTA enhanced bimetallic Al0–Fe0/O2 process was also investigated. The results showed the EDTA enhanced effect may be attributed to the complex formed by EDTA and Fe(II) rather than Al(III). The EDTA enhanced Al0–Fe0/O2 process exhibited higher reactivity than Al0/O2, Al0 + EDTA/O2, Fe0/O2 and Fe0 + EDTA/O2 process. 50 mg L−1 of 4-bromophenol could be completely degraded in 1 h with the 1:1 mass ratio of Al0 and Fe0. Accordingly, 4-bromophenol was attacked by OH to achieve complete de-bromine and low molecular weight organic acids, even mineralized. The degradation pathway of 4-bromophenol in EDTA enhanced Al0–Fe0/O2 may follow 4-bromocatechol and hydroquinone pathway.