College of Environment, Zhejiang University of Technology, Hangzhou 310014, China.
R&D Center of Zhejiang Zone-King Environment Co., Ltd, Hangzhou, 310014, China.
Sci Total Environ. 2019 Feb 10;650(Pt 1):419-426. doi: 10.1016/j.scitotenv.2018.09.003. Epub 2018 Sep 3.
Mechanochemically sulfidated microscale zero valent iron (S-mZVI) is a promising groundwater remediation material as it has been proven to be not only efficient in dechlorinating chlorinated compounds but also amenable to up-scaling. Yet, its efficiency in treating metal contaminants remains barely studied. In this study, we investigated the mechanism and efficiencies of Cr(VI) removal by S-mZVI and its effect on TCE dechlorination as a co-contaminant. The Cr(VI) removal by S-mZVI was mainly a chemisorption process and its kinetics was well fitted by a pseudo-second-order model. Alkaline pH inhibited Cr(VI) removal while dissolved oxygen slightly depressed the Cr(VI) removal. The Cr(VI) removal rapidly formed a non-conductive layer on S-mZVI surface to hinder further electron transfer from Fe core before H was able to accept any electrons to produce H, which resulted in 100% electron efficiencies of Cr(VI) removal but <1% of Fe utilization efficiency. The presence of Cr(VI) also dramatically inhibited the dechlorination of TCE and its electron efficiency as a co-contaminant by passivating the FeS surface. Therefore, Cr(VI) is likely to be an electron sink if present for remediation of other contaminants in groundwater.
机械化学硫化的微尺度零价铁（S-mZVI）是一种很有前途的地下水修复材料，因为它不仅被证明在脱氯氯化物方面非常有效，而且易于扩大规模。然而，它处理金属污染物的效率几乎没有被研究过。在这项研究中，我们研究了 S-mZVI 去除 Cr(VI)的机制和效率，以及其作为共污染物对 TCE 脱氯的影响。S-mZVI 对 Cr(VI)的去除主要是一个化学吸附过程，其动力学很好地符合准二级模型。碱性 pH 抑制了 Cr(VI)的去除，而溶解氧则略微抑制了 Cr(VI)的去除。Cr(VI)的去除在 H 能够接受任何电子产生 H 之前，迅速在 S-mZVI 表面形成一个不导电的层，阻碍从 Fe 核心进一步转移电子，导致 Cr(VI)去除的电子效率达到 100%，但 Fe 的利用率仅<1%。Cr(VI)的存在也极大地抑制了 TCE 的脱氯及其作为共污染物的电子效率，因为它使 FeS 表面钝化。因此，如果要修复地下水中的其他污染物，Cr(VI)很可能是一个电子汇。
