Role of weak magnetic field for enhanced oxidation of orange G by magnetic Fenton

The role of weak magnetic field (WMF) on the degradation of a common textile azo-dye, orange G (OG), by magnetic Fenton system was investigated in detail. The results showed that the presence of WMF can provide better performance of the Fe3O4/H2O2 system for OG degradation. The optimized reaction conditions were contained at 1 mM Fe3O4 as Fe, 20 mT of magnetic field intensity, 20 mM H2O2, and initial pH of 3.0. The removal efficiency of OG by Fe3O4/H2O2 coupling with WMF increased largely from 56.3 to 82.3% compared with Fe3O4/H2O2 process. Both the electron paramagnetic resonance (EPR) analysis and the quenching effect of tert-butyl alcohol (TBA) confirmed that hydroxyl radical (•OH) was the primary reactive oxygen species in WMF-Fe3O4/H2O2 system. The improving effect of WMF was explained by the magnetoconvection theory. The presence of WMF could accelerate the corrosion rate of Fe3O4 and thus promoted the release of Fe(II), which led to the increased production of •OH and enhanced the degradation of OG. Moreover, it was surprising to observe that the WMF induced improvement in OG degradation by heterogeneous Fenton involving the iron sludge, namely FeOOH and Fe2O3, as catalysts. These results indicated that WMF could be utilized as an efficient and cost-effective strategy to improve the removal of organic pollutants by iron oxide–based Fenton process.