Influence of calcium ions on the colloidal stability of surface-modified nano zero-valent iron in the absence or presence of humic acid
Influence of calcium ions on the colloidal stability of surface-modified nano zero-valent iron in the absence or presence of humic acid
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DOI：
10.1016/j.watres.2013.02.022
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发表时间：
2013-05-01
期刊：
影响因子：
12.8
通讯作者：
Lo, Irene M. C.
中科院分区：
文献类型：
--
作者：
Dong, Haoran;Lo, Irene M. C.
为了减少纳米零价铁（NZVI）在地下水原位修复中的聚集，提高其迁移率，必须使用有机稳定剂对纳米零价铁（NZVI）的表面进行改性，这些稳定剂可以提供静电排斥和空间或静电稳定。然而，纳米颗粒的稳定性也会受到地下水成分如阳离子和腐植酸（HA）的影响。在本研究中，评估了Ca2+对三种稳定剂（即聚丙烯酸（FAA）， Tween-20和淀粉）包被的NZVI在没有或存在HA的情况下胶体稳定性的影响。观察到不同表面改性的NZVIs的稳定性行为不同。在没有或存在HA的情况下，Ca2+的存在对FAA或Tween-20修饰的NZVI的沉降有轻微影响。然而，Ca2+的存在导致淀粉修饰的NZVI在没有HA的情况下发生明显的聚集和沉降，并且在有HA的情况下诱导更高程度的聚集和沉降。我们推测，在没有HA的情况下，淀粉修饰的NZVI颗粒通过Ca2+络合作用与颗粒表面被包裹的淀粉分子相互附着，从而增强了淀粉修饰的NZVI的聚集和随后的沉降。然而，在HA存在的情况下，淀粉修饰的NZVI聚集体的光谱分析表明，HA与Ca2+的桥接相互作用是增强聚集体的主要机制。(C) 2013 Elsevier Ltd.版权所有。
To decrease aggregation and enhance the mobility of nano zero-valent iron (NZVI) used for in-situ groundwater remediation, the surface of such NZVI must be modified using organic stabilizers, which can provide electrostatic repulsion, and steric or electrosteric stabilization. However, the stability of the nanoparticles can also be affected by groundwater components such as cations and humic acid (HA). In this study, the effect of Ca2+ on the colloidal stability of NZVI coated with three types of stabilizers (i.e., polyacrylic acid (FAA), Tween-20 and starch) was evaluated in the absence or presence of HA. Differing stability behavior was observed for different surface-modified NZVIs. The presence of Ca2+ exerted a slight influence on the settling of NZVI modified with FAA or Tween-20, in the absence or presence of HA. However, the presence of Ca2+ caused significant aggregation and sedimentation for starch-modified NZVI in the absence of HA, and induced an even higher degree of aggregation and sedimentation in the presence of HA. It is presumed that, in the absence of HA, starch-modified NZVI particles undergo attachment with each other via Ca2+ complexation with the coated starch molecules on the surface of the particles, thus enhancing the aggregation and the following sedimentation of starch-modified NZVI. However, in the presence of HA, spectroscopic analysis of the starch-modified NZVI aggregates indicated that the bridging interaction of HA with Ca2+ was the predominant mechanism for the enhanced aggregation. (C) 2013 Elsevier Ltd. All rights reserved.