Novel Fenton-like system (Mg/Fe-O₂) for degradation of 4-chlorophenol

A novel heterogeneous Fenton-like system (Mg/Fe-O₂) which could directly convert oxygen (O₂) to hydrogen peroxide/hydroxyl radicals (H₂O₂/^•OH) was developed and used to degrade 4-chlorophenol. The Mg/Fe bimetallic particles were prepared by chemical displacement process and characterized by XRD, SEM and TEM. The in situ continuous production of H₂O₂/^•OH and the effect of the mole ratio of Mg to Fe in the Mg/Fe bimetallic particles and the operating parameters on the degradation 4-chlorophenol in Mg/Fe-O₂ system were investigated in detail. It was found that the Mg/Fe bimetallic particles with the mole ratio of Mg to Fe of 32:1 had the best performance for the 4-chlorophenol degradation and the maximum cumulative concentration of H₂O₂, the degradation efficiency of 4-chlorophenol and the removal efficiency of TOC in Mg/Fe-O₂ system were 34.5 mg/L, 100% and 91.8%, respectively, at pH 3, O₂ flow rate 400 mL/min, dosage of Mg/Fe bimetallic particles 2 g/L, 4-chlorophenol initial concentration 50 mg/L and reaction time 60 min. It was revealed by radical scavenging experiments that ^•OH, particularly the surface-bound ^•OH, were the predominant reactive oxygen species in Mg/Fe-O₂ system for the degradation of 4-chlorophenol. The main intermediates of 4-chlorophenol degradation were detected by high-resolution liquid chromatography equipped with time-of-flight mass spectrometry (HRLC-ToF-MS) and ion chromatography (IC). Based the results of control experiments and the electrochemical tests, the possible pathway and mechanism of 4-chlorophenol degradation in Mg/Fe-O₂ system were tentatively proposed.