Sulfidation of Nano Zerovalent Iron (nZVI) for Improved Selectivity During In-Situ Chemical Reduction (ISCR)
Sulfidation of Nano Zerovalent Iron (nZVI) for Improved Selectivity During In-Situ Chemical Reduction (ISCR)
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DOI：
10.1021/acs.est.6b02170
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发表时间：
2016-09-06
影响因子：
11.4
通讯作者：
Johnson, Richard L.
中科院分区：
文献类型：
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作者：
Fan, Dimin;Johnson, Graham O'Brien;Johnson, Richard L.
纳米零价铁（nZVI）的高反应性导致由于与各种天然还原剂需求（NRD）过程的竞争，特别是水还原成氢的过程而导致处理效率低下。在这里，我们表明这种限制可以通过硫化（即通过减少硫化合物进行改性）来缓解。在羧甲基纤维素上合成的 nZVI (CMC-nZVI) 用硫化物或连二亚硫酸盐进行硫化。通过三种互补测定法检查所得材料的反应性：（i）直接测量氢气产量，（ii）比色氧化还原探针（靛蓝二磺酸盐，I2S）的还原，以及（iii）三氯乙烯（TCE）脱氯。结果表明，S/Fe摩尔比>0.3时的硫化有效消除了与水的反应，但保留了与TCE的显着反应活性。然而，硫化物的硫化使大部分 nZVI 成为 Fe(0)，而连二亚硫酸盐将大部分 nZVI 转化为 FeS（从而消耗了大部分最初由 Fe(0) 提供的还原能力）。简化数值模型表明，12S和TCE的还原动力学主要取决于初始还原当量，并且TCE还原率受FeS老化的影响。总体而言，结果表明，用还原性硫化合物预处理 nZVI 可以显着提高 nZVI 选择性。
The high reactivity of nano zerovalent iron (nZVI) leads to inefficient treatment due to competition with various natural reductant demand (NRD) processes, especially the reduction of water to hydrogen. Here we show that this limitation can be alleviated by sulfidation (i.e., modification by reducing sulfur compounds). nZVI synthesized on carboxylmethylcelluose (CMC-nZVI) was sulfidated with either sulfide or dithionite. The reactivity of the resulting materials was examined with three complementary assays: (i) direct measurement of hydrogen production, (ii) reduction of a colorimetric redox probe (indigo disulfonate, I2S), and (iii) dechlorination of trichloroethylene (TCE). The results indicate that sulfidation at S/Fe molar ratios of >0.3, effectively eliminates reaction with water, but retains significant reactivity with TCE. However, sulfidation with sulfide leaves most of the nZVI as Fe(0), whereas dithionite converts a majority of the nZVI to FeS (thus consuming much of the reducing capacity originally provided by the Fe(0)). Simplified numerical models show that the reduction kinetics of 12S and TCE are mainly dependent on the initial reducing equivalents and that the TCE reduction rate is affected by the aging of FeS. Overall, the results suggest that pretreatment of nZVI with reducing sulfur compounds could result in substantial improvement in nZVI selectivity.