Investigation of washing and storage strategy on aging of Mg-aminoclay (MgAC) coated nanoscale zero-valent iron (nZVI) particles
Investigation of washing and storage strategy on aging of Mg-aminoclay (MgAC) coated nanoscale zero-valent iron (nZVI) particles
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DOI：
10.1016/j.ces.2014.08.002
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发表时间：
2014-11
影响因子：
4.7
通讯作者：
Y. Hwang;Young-Chul Lee;Paul D. Mines;Y. Oh;J. Choi;H. Andersen
中科院分区：
文献类型：
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作者：
Y. Hwang;Young-Chul Lee;Paul D. Mines;Y. Oh;J. Choi;H. Andersen
纳米级零价铁（nZVI）颗粒的团聚和氧化倾向限制了其在原位地下水和土壤修复中的应用。虽然表面涂层对纳米粒子稳定性的影响已经被广泛应用，但制备工艺对稳定nZVI老化的影响还需要进一步研究。在长达7天的洗涤和储存过程中，对mg -氨基clay （MgAC）涂层nZVI老化的影响进行了评估，以下三个步骤：用1mm nahco3溶液洗涤前和储存后，用稳定剂（MgAC）溶液洗涤。即使初始粒径相同，预洗后的nZVI粒径也增加了6倍。这种高聚集倾向似乎是由于洗涤和储存过程中MgAC的解吸，正如zeta电位的降低所证实的那样，表明nZVI颗粒之间的排斥力减少。另一方面，为了保持nZVI的反应活性，通过去除合成混合物中的残留反应物，储存前洗涤是必不可少的。nZVI的反应性通过三个参数进行考察：508 nm光密度（测量颗粒浓度）、酸消化H2generation法测定活性铁含量和硝酸还原能力。洗涤后的nZVI的这三个参数都显著降低，这与XRD结果相对应，表明Fe(0)转变为氧化铁。反应性测试显示出高度的线性相关性（r2>0.95,p<0.05）。储存前洗涤，然后加入MgAC，表现出高稳定性的储存前洗涤，以及高反应活性的储存后洗涤。在这里，我们发现适当的洗涤程序在涂层nZVI制备中是至关重要的，以提供持久的稳定性，并在制备和运输过程中保持反应能力。
The tendency towards agglomeration and oxidation of nanoscale zero-valent iron (nZVI) particles limits its application for in situ groundwater and soil remediation. Although the effect of surface coatings on nanoparticle stabilization has been commonly practiced, the effect of preparation procedures on aging of stabilized nZVI needs to be investigated. The effect of washing and storage, up to seven days, on aging of Mg-aminoclay (MgAC) coated nZVI is evaluated, following three procedures: pre- and post-storage washing with a 1 mM NaHCO3solution, and pre-storage washing with a stabilizer (MgAC) solution. Even though the initial particle size is identical, the observed size of pre-washed nZVI increases up to six times. This high aggregation tendency appears to be due to the desorption of MgAC during washing and storage, as verified by a decrease in the zeta potential, indicating a decrease of repulsion between nZVI particles. On the other hand, pre-storage washing is essential, in order to retain nZVI reactivity, by removal of residual reactants in the synthesis mixture. The reactivity of nZVI is examined with three parameters: optical density at 508 nm as a measure of particle concentration, reactive iron content measured by H2generation with acid digestion, and nitrate reduction capacity. All three parameters decrease significantly for post-storage washed nZVI, which corresponds to XRD results that exhibit transformation of Fe(0) to iron oxides. The reactivity tests display high linear correlations (r2>0.95,p<0.05) with respect to one another. Pre-storage washing, followed by addition of MgAC, exhibits high stability as pre-storage washing, as well as high reactivity as post-storage washing. Here, it is found that the proper washing procedure is crucial in coated nZVI preparation, to provide long lasting stability and to maintain reaction capacity during its preparation and transport.