Department of Civil and Environmental Engineering, University of Auckland, Auckland, New Zealand.
Department of Civil Engineering, University of Moratuwa, Moratuwa, Sri Lanka.
Environ Sci Pollut Res Int. 2018 Jun;25(18):17797-17806. doi: 10.1007/s11356-018-2003-5. Epub 2018 Apr 20.
The dechlorination of chlorinated organic pollutants by zero valent iron (ZVI) is an important water treatment process with a complex dependence on many variables. This complexity means that there are reported inconsistencies in terms of dechlorination with ZVI and the effect of ZVI acid treatment, which are significant and are as yet unexplained. This study aims to decipher some of this complexity by combining Raman spectroscopy with gas chromatography-mass spectrometry (GC-MS) to investigate the influence of the mineralogy of the iron oxide phases on the surface of ZVI on the reductive dechlorination of pentachlorophenol (PCP). Two electrolytic iron samples (ZVI-T and ZVI-H) were found to have quite different PCP dechlorination reactivity in batch reactors under anoxic conditions. Raman analysis of the "as-received" ZVI-T indicated the iron was mainly covered with the ferrous oxide (FeO) wustite, which is non-conducting and led to a low rate of PCP dechlorination. In contrast, the dominant oxide on the "as-received" ZVI-H was magnetite which is conducting and, compared to ZVI-T, the ZVI-H rate of PCP dechlorination was four times faster. Treating the ZVI-H sample with 1 N HSO made small change to the composition of the oxide layers and also minute change to the rate of PCP dechlorination. However, treating the ZVI-T sample with HSO led to the loss of wustite so that magnetite became the dominant oxide and the rate of PCP dechlorination increased to that of the ZVI-H material. In conclusion, this study clearly shows that iron oxide mineralogy can be a contributing factor to apparent inconsistencies in the literature related to ZVI performance towards dechlorination and the effect of acid treatment on ZVI reactivity.
零价铁（ZVI）脱氯是一种重要的水处理工艺，对许多变量有复杂的依赖性。这种复杂性意味着，据报道，ZVI 的脱氯作用以及 ZVI 酸处理的效果存在不一致之处，而且这些不一致之处非常显著，但尚未得到解释。本研究旨在通过结合拉曼光谱和气相色谱-质谱（GC-MS）来研究氧化铁相的矿物学对 ZVI 表面还原脱氯五氯苯酚（PCP）的影响，从而破解这种复杂性。在缺氧条件下的批式反应器中，发现两种电解铁样品（ZVI-T 和 ZVI-H）的 PCP 脱氯反应活性有很大差异。对“原样”ZVI-T 的拉曼分析表明，铁主要覆盖有亚铁氧化物（FeO）的磁铁矿，它是不导电的，导致 PCP 脱氯速率很低。相比之下，“原样”ZVI-H 上主要的氧化物是导电的磁铁矿，与 ZVI-T 相比，ZVI-H 的 PCP 脱氯速率快了四倍。用 1 N HSO 处理 ZVI-H 样品对氧化物层的组成和 PCP 脱氯速率只有微小的改变。然而，用 HSO 处理 ZVI-T 样品会导致磁铁矿失去 wustite，从而使磁铁矿成为主要的氧化物，PCP 脱氯速率增加到与 ZVI-H 材料相当的水平。总之，本研究清楚地表明，氧化铁的矿物学可能是导致文献中关于 ZVI 脱氯性能和酸处理对 ZVI 反应性影响的不一致的一个因素。
