预磁化对零价铁反应活性影响的探究

Influence of Pre- magnetization on Reactivity of Zero-valent Iron

考察了预磁化对四种不同来源的零价铁反应活性的影响。结果表明,在预磁化磁场强度0~600 mT范围内,其对零价铁腐蚀的促进效果呈现先增强后变缓的变化趋势。ZVI-33.1、ZVI-Aldrich、ZVI-Fisher、ZVI-7.4四种铁粉的饱和预磁化磁场强度分别为50 mT、50 mT、100 mT及300 mT。达到饱和磁场强度后,继续加大磁场强度,预磁化的促进作用不再进一步提高。总体上,预磁化对粒径小、初始活性较低的零价铁的促进效果更明显。不同场强预磁化对零价铁去除Se（IV）具有相似的影响规律,200 mT时即可达到最大的去除效果,且零价铁对Se（IV）的去除效果与无污染物时Fe（Ⅱ）的释放速度呈现很好的线性关系。预磁化促进零价铁反应活性提高的主要原因是零价铁被磁化后存在一定剩磁,引起表面不均匀腐蚀,有效减缓零价铁表面钝化从而提高零价铁的反应活性。

The effects of magnetic field intensity of pre - magnetization on four types of ZVI from different origins were symmetrically investigated in this paper. The results showed that the promotion effect of pre - magnetization on ZVI corrosion increased greatly followed by a slow down as the intensity of pre - magnetization increased from 0 mT to 600 roT. The saturated magnetic intensity （SIM） of ZVI - 33. I, ZVI - Aldrich, ZVI - Fisher, and ZVI - 7.4 were 50 roT, 50 roT, 100 mT and 300 mT respectively. The promotion effect of pre - magnetization stays the same after reaching the saturated magnetic intensity despite increasing the intensity of the magnetic field. Generally, pre - magnetization had much more obvious positive effect on the iron particles with smaller grain size and lower reactivity. Se（IV） removal by ZVI was enhanced with the increasing magnetic field intensity for pre -magnetization, until the SMI reaches 200 roT. Notably, there was a strong linear correlation between Se （IV） removal efficiency by ZVI and the intrinsic Fe （ II ） release rate in the absence of any substrate. The enhanced reactivity of ZVI by pre - magnetization should be mainly associated with the magnetic memory effect （ i. e. , the remanence kept by ZVI） that caused the surface heterogeneous corrosion of ZVI and mediated the passivation of ZVI, thus improved the reactivity of ZVI.