Anisotropic oxidative growth of goethite-coated sand particles in column reactors during 4-chloronitrobenzene reduction by Fe( ii )/goethite
Anisotropic oxidative growth of goethite-coated sand particles in column reactors during 4-chloronitrobenzene reduction by Fe( ii )/goethite
复制标题
Fe( ii )/针铁矿还原4-氯硝基苯过程中塔式反应器中针铁矿包覆砂粒的各向异性氧化生长
DOI：
10.1039/d1en00788b
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Arnold, William A.
中科院分区：
文献类型：
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作者：
Soroush, Adel;Penn, R. Lee;Arnold, William A.
缺氧含水层中的高活性还原剂铁氧化物与Fe(II)缔合还原地下水中的一类重要污染物硝基芳香族化合物(NaCS)已得到广泛研究，但实验室控制良好的间歇反应器条件与现场遇到的复杂条件存在显著差异。连续流动柱反应器包含针铁矿涂层砂和碳酸盐缓冲液，连续暴露在0.05 mm对氯硝基苯(4-ClNB)和0.5 mm Fe(II)中，以模拟更真实的场景，并能够在饱和和不饱和流动条件下研究针铁矿颗粒的氧化生长。这些实验旨在测试附着在表面上如何影响颗粒生长，以及颗粒生长如何随着时间的推移影响反应的程度。反应结束后，从每个柱子的不同部分收集颗粒，并将针铁矿从沙粒中分离出来，用透射电子显微镜进行表征。氧化生长的量随距离柱进口的距离而变化，最大的生长在柱的入口端(底部)观察到。与前人使用间歇反应器的工作类似，新氧化的Fe(III)主要被添加到针铁矿颗粒尖端，导致在饱和流动下长度增加81%，在220孔体积后在非饱和流动下增加50%。在饱和流动条件下，反应物浓度和反应程度是决定矿物生长程度的重要因素。然而，对于未饱和的柱条件，流动路径对柱中的矿物生长有很大影响。在饱和流动条件下，220孔体积后牺牲的反应器导致针铁矿质量总体增加70%，而不饱和流动柱导致针铁矿质量增加40%，矿物生长随进口距离的变化而增加，总体上4-ClNB转化率降低50%。结果表明，定量表征附着在底层矿物上的针铁矿纳米颗粒的氧化矿物生长是可行的，并阐明了在受污染的地下水系统中影响矿物纳米颗粒反应活性的主要变量。
Reduction of nitroaromatic compounds (NACs), an important class of groundwater pollutants, by Fe(II) associated with iron oxides, a highly reactive reductant in anoxic aquifers, has been studied widely, but there are significant differences between the well-controlled, batch reactor conditions of the laboratory and the complicated conditions encountered in the field. Continuous flow column reactors containing goethite-coated sand and aqueous carbonate buffer were continuously exposed to 0.05 mM 4-chloronitrobenzene (4-ClNB) and 0.5 mM Fe(II) to emulate more realistic scenarios and to allow study of the oxidative growth of goethite particles using both saturated and unsaturated flow conditions. The experiments were designed to test how attachment to a surface affected particle growth and how particle growth affected the extent of reaction over time. After reaction, particles from different sections of each column were collected, and the goethite was detached from the sand grains for characterization using transmission electron microscopy. The amount of oxidative growth varied as a function of distance from the column inlet, with the most growth observed at the inlet end (bottom) of the column. Similar to previous work using batch reactors, newly oxidized Fe(III) was mostly added to the goethite particle tips, resulting in up to an 81% increase in length under saturated flow and a 50% increase in length under unsaturated flow after 220 pore volumes. With saturated flow, reactant concentrations and the extent of the reaction are important factors determining the extent of mineral growth. For unsaturated column conditions, however, flow path substantially impacts mineral growth in the column. Reactors sacrificed after 220 pore volumes under saturated flow conditions resulted in an overall 70% increase in goethite mass while the unsaturated flow column resulted in a 40% increase in goethite mass, more variable mineral growth as a function of distance from the inlet, and overall, 50% less 4-ClNB conversion. The results demonstrate that quantitative characterization of oxidative mineral growth of goethite nanoparticles attached to an underlying mineral is practical and elucidates the major variables impacting the reactivity of mineral nanoparticles in contaminated groundwater systems.