Effect of magnetic field on the zero valent iron induced oxidation reaction

The magnetic field (MF) effect on the zero valent iron (ZVI) induced oxidative reaction was investigated for the first time. The degradation of 4-chlorophenol (4-CP) in the ZVI system was employed as the test oxidative reaction. MF markedly enhanced the degradation of 4-CP with the concurrent production of chlorides. The consumption of dissolved O₂ by ZVI reaction was also enhanced in the presence of MF whereas the competing reaction of H₂ production from proton reduction was retarded. Since the ZVI-induced oxidation is mainly driven by the in situ generated hydroxyl radicals, the production of OH radicals was monitored by the spin trap method using electron spin resonance (ESR) spectroscopy. It was confirmed that the concentration of trapped OH radicals was enhanced in the presence of MF. Since both O₂ and Fe⁰ are paramagnetic, the diffusion of O₂ onto the iron surface might be accelerated under MF. The magnetized iron can attract oxygen on itself, which makes the mass transfer process faster. As a result, the surface electrochemical reaction between Fe⁰ and O₂ can be accelerated with the enhanced production of OH radicals. MF might retard the recombination of OH radicals as well.