Influence of fulvic acid on the colloidal stability and reactivity of nanoscale zero-valent iron
Influence of fulvic acid on the colloidal stability and reactivity of nanoscale zero-valent iron
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黄腐酸对纳米零价铁胶体稳定性和反应活性的影响
DOI：
10.1016/j.envpol.2016.01.017
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发表时间：
2016-04-01
影响因子：
8.9
通讯作者：
Zeng, Yalan
中科院分区：
文献类型：
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作者：
Dong, Haoran;Ahmad, Kito;Zeng, Yalan
研究了黄腐酸（FA）在pH为5、7和9时对纳米零价铁（nZVI）胶体稳定性和反应性的影响。nZVI在不同ph下的沉降行为不同。采用双相模型描述了两个随时间变化的沉降过程（即快速沉降后缓慢沉降），并计算了沉降速率。一般来说，nZVI在零电荷点（pH(pzc)）的沉降更为显著，由于FA在nZVI表面的吸附，在FA存在的情况下，pH（pzc）的沉降会发生变化。pH值为5 ~ 7时，吸附在nZVI表面的FA比pH值为9时多，通过影响颗粒间的静电斥力导致了nZVI的沉降行为发生变化。此外，我们还发现，由于FA的存在，nZVI的稳定性和反应性之间存在权衡。当FA浓度较低时，FA在nZVI表面的吸附可以增强颗粒的稳定性，从而通过提供更多的有效表面位点来促进Cr（VI）的还原。然而，当FA浓度过高而不能占据nZVI的表面活性位点时，即使FA增强了nZVI颗粒的分散，Cr（VI）的还原也会降低。在pH为9时，FA提高了nZVI对Cr（VI）的还原。考虑到FA在nZVI表面的吸附不明显，对nZVI颗粒沉降行为的影响很小，提出FA与生成的Fe(III)/Cr（III）离子形成可溶性配合物，从而降低了nZVI表面的钝化程度，促进了Cr（VI）的还原。(C) 2016 Elsevier Ltd.版权所有。
This study investigated the effect of fulvic acid (FA) on the colloidal stability and reactivity of nano zero-valent iron (nZVI) at pH 5, 7 and 9. The sedimentation behavior of nZVI differed at different pH. A biphasic model was used to describe the two time-dependent settling processes (i.e., a rapid settling followed by a slower settling) and the settling rates were calculated. Generally, the settling of nZVI was more significant at the point of zero charge (pH(pzc)), which could be varied in the presence of FA due to the adsorption of FA on the nZVI surface. More FA was adsorbed on the nZVI surface at pH 5-7 than pH 9, resulting in the varying sedimentation behavior of nZVI via influencing the electrostatic repulsion among particles. Moreover, it was found that there was a tradeoff between the stabilization and the reactivity of nZVI as affected by the presence of FA. When FA concentration was at a low level, the adsorption of FA on the nZVI surface could enhance the particle stabilization, and thus facilitating the Cr(VI) reduction by providing more available surface sites. However, when the FA concentrations were too high to occupy the active surface sites of nZVI, the Cr(VI) reduction could be decreased even though the FA enhanced the dispersion of nZVI particles. At pH 9, the FA improved the Cr(VI) reduction by nZVI. Given the adsorption of FA on the nZVI surface was insignificant and its effect on the settling behavior of nZVI particles was minimal, it was proposed that the FA formed soluble complexes with the produced Fe(III)/Cr(III) ions, and thus reducing the degree of passivation on the nZVI surface and facilitating the Cr(VI) reduction. (C) 2016 Elsevier Ltd. All rights reserved.