Weak magnetic field enhances the activation of peroxymonosulfate by ZnO@Fe 3 O 4 .

The effect of weak magnetic field (WMF) on Acid Orange 7 (AO7) removal by ZnO@Fe 3 O 4 /peroxymonosulphate (PMS) was investigated. The results showed that the AO7 sequestration rate enhanced progressively to 0.14183 min -1 in the presence of WMF, approximately 3 times the 0.04966 min -1 in the absence of WMF. SO 4 ˙ - /SO 5 ˙ - and O 2 ˙ - radicals were generated from the decomposition of PMS catalyzed by ZnO@Fe 3 O 4 causing the degradation of AO7. In addition, a weak magnetic field promoted the production of O 2 ˙ - radicals and transition of Fe 3+ to Fe 2+ . Radical-pair theory was used in this study to describe the role of WMF and a possible reaction mechanism was derived. Based on that, the influence of magnetic field flux intensity, pH and the reusability of ZnO@Fe 3 O 4 were investigated in this paper.