Enhanced peroxymonosulfate activation by coupling zeolite-supported nano-zero-valent iron with weak magnetic field

In this study, notable peroxymonosulfate (PMS) activation enhancement accomplished by coupling zeolite supported nano-zero-valent Iron (z-nZVI) with weak magnetic field (WMF) was reported. The z-nZVI/PMS/WMF possessed 25% enhancement (when pH = 3) in acid orange 7 (AO7) removal efficiency and 2-3 folds enhancement in degradation rate and could extend pH range when compared with z-nZVI/PMS process. SEM mapping and XRD analysis revealed that WMF accelerated the dissolution of z-nZVI to promote the formation of free radicals. Electron paramagnetic resonance (EPR) spectroscopy and radical scavenger studies verified the formation of SO4(center dot-), (OH)-O-center dot and O-2(center dot-). It was demonstrated that the generation of O-2(center dot-) was due to the reaction of Fe-0 with PMS rather than the diffusion of O-2. The role of WMF was explained by the magnetoconvection theory and a possible reaction mechanism was derived. The significant improvement was also observed on the degradation of other contaminants including tetracycline and norfloxacin (50% enhancement). Moreover, regenerating z-nZVI by recycled zeolites makes water treatment much easier, more feasible and more economical.