摘要：
Zero-valent iron (ZVI),a simple but amazingly versatile material,has low intrinsic reactivity toward various contaminants as documented from laboratory studies as well as field demonstrations,which poses potential limitations to its practical application in environmental remediation.Although many methods have been developed to improve the reactivity of ZVI in the literature,high costs,significant work-load,and complex operations may inhibit the application of these methods.We pioneered the research in employing weak magnetic field (WMF) to accelerate the removal of various metal(loid)s,including Se(Ⅳ)/Se(Ⅵ),As(Ⅴ)/As(Ⅲ),Sb(Ⅴ),Cu(Ⅱ)/EDTA-Cu(Ⅱ),and Cr(Ⅵ) by pristine ZVI (Pri-ZVI) and/or aged ZVI.The rate constants of metal(loid)s sequestration by Pri-ZVI or aged ZVI were increased by 1.1～383.7 folds due to the application of WMF.Furthermore,WMF could be employed to improve the removal of organic contaminants by ZVI activated H2O2 or persulfate because of the accelerated ZVI corrosion in the presence of WMF.The superimposed WMF had negligible influence on the apparent activation energy of metal(loid)s removal by ZVI,indicating that WMF accelerated metal(loid)s removal by ZVI but did not change the mechanisms.The XAFS,XRD,and XPS analysis confirmed that the application of WMF did not change the mechanisms of metal(loid)s removal but accelerated the transformation (reduction or oxidation) of contaminants.Electrochemical analysis showed that the accelerated ZVI corrosion in the presence of WMF was ascribed to the enhanced mass transfer.We further identified the relative contribution of Lorentz force (FL) and magnetic gradient force (F△B) in the enhancing effect of WMF.It suggested that F△B rather than FL was the major driving force for the observed WMF effect on the enhanced reactivity of ZVI.Moreover,we proposed to apply premagnetization to increase the reactivity of ZVI toward As(Ⅲ) sequestration taking advantage of the magnetic memory of ZVI,i.e.,the remanence of ZVI.In addition,the premagnetized ZVI (Mag-ZVI) samples from different origins were applied to enhance the removal of various oxidative contaminants [such as azo dyes,As(Ⅲ),Pb(Ⅱ),Cu(Ⅱ),Se(Ⅳ),Ag(Ⅰ) and Cr(Ⅵ)] under well-controlled experimental conditions.The rate constants of contaminants removal by premagnetized ZVI samples were 1.2～12.2 folds greater than those by Pri-ZVI samples.As a chemical-and energy-free method,improving the reactivity of ZVI by either WMF superimposition or premagnetization treatment is novel and promising.%作为一种环境友好、价格低廉的水处理药剂,零价铁(ZVI)的低反应活性已成为基于ZVI水处理技术工程应用的一个重要障碍.如何提高ZVI对污染物的去除已成为目前研究的焦点,作者课题组近年来围绕探究弱磁场(WMF)对ZVI除有毒污染物的正面效应及其作用机制展开了系列研究.该系列工作明确了WMF能够提高ZVI对有毒金属离子的去除速率,探明了WMF强化ZVI除污染的作用机制主要是通过磁场梯度力实现的.为进一步探索磁场对零价铁除污染的正面效应,作者提出通过磁场预磁化来提高ZVI对水中污染物的反应活性,且考察了该方法强化不同来源零价铁去除不同污染物的广谱性.利用WMF强化ZVI对水中污染物的去除具有高效、操作简单、低成本、适用广泛以及无二次污染等优点,因而利用WMF是一种应用前景广阔的提高ZVI活性的水处理技术.
