Effect of Coexisting Fe(III) (oxyhydr)oxides on Cr(VI) Reduction by Fe(II)-Bearing Clay Minerals
Effect of Coexisting Fe(III) (oxyhydr)oxides on Cr(VI) Reduction by Fe(II)-Bearing Clay Minerals
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共存 Fe(III)（羟基）氧化物对含 Fe(II) 粘土矿物还原 Cr(VI) 的影响
DOI：
10.1021/acs.est.9b05208
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发表时间：
2019-12-03
影响因子：
11.4
通讯作者：
Cheng, Dong
中科院分区：
文献类型：
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作者：
Liao, Wenjuan;Ye, Zilu;Cheng, Dong
含Fe（II）的粘土矿物是地下环境中Cr（VI）还原的重要电子源。然而，目前尚不清楚铁（羟基）氧化物如何影响含铁（II）粘土的Cr（VI）还原，因为这两种矿物可以共存于土壤和沉积物聚集体中。研究了还原绿脱石NAu-2（rNAu-2）和水铁矿（Fe（II）/Cr（VI）= 3：1）混合悬浮液中Cr（VI）的还原。当矿物预混时间从0增加到72 h时，初始阶段Cr（VI）的还原显著加速，而Cr（VI）的吸附则受到显著抑制。矿物预混导致电子转移从结构铁（II）在rNAu-2的水铁矿与形成的反应性表面相关的铁（II），催化水铁矿转化为纤铁矿。反应性表面相关的Fe（II）加速Cr（VI）的还原最初，和水铁矿转化为纤铁矿是负责抑制吸附。当反应性表面相关的Fe（II）在初始阶段被消耗时，Cr（VI）的还原速率急剧下降，这是由于从rNAu-2中的结构Fe（II）到表面反应性位点的缓慢电子转移的限制。当rNAu-2与水铁矿共存时，主要还原位点由rNAu-2向水铁矿/纤铁矿转移。我们的研究结果表明，矿物之间的电子转移具有重要意义的Cr（VI）和其他高价污染物还原铁（II）的粘土矿物在地下环境中。
Fe(II)-bearing clay minerals are important electron sources for Cr(VI) reduction in subsurface environments. However, it is not clear how iron (oxyhydr)oxides impact Cr(VI) reduction by Fe(II)-bearing clays as the two minerals can coexist in soil and sediment aggregates. This study investigated Cr(VI) reduction in the mixed suspensions of reduced nontronite NAu-2 (rNAu-2) and ferrihydrite (Fe(II)/Cr(VI) = 3:1). When the mineral premixing time increased from 0 to 72 h, Cr(VI) reduction was accelerated prominently in the initial stage, while Cr(VI) sorption was inhibited drastically. Mineral premixing led to electron transfer from structural Fe(II) in rNAu-2 to ferrihydrite with formation of reactive-surface-associated Fe(II), which catalyzed ferrihydrite transformation to lepidocrocite. Reactive-surface-associated Fe(II) accelerated Cr(VI) reduction initially, and ferrihydrite transformation to lepidocrocite was responsible for the inhibited sorption. When the reactive-surface-associated Fe(II) was consumed in the initial stage, the Cr(VI) reduction rate decreased dramatically due to the limitation of slow electron transfer from structural Fe(II) in rNAu-2 to surface-reactive sites. The main reduction sites shifted from rNAu-2 to ferrihydrite/lepidocrocite when rNAu-2 coexisted with ferrihydrite. Our findings demonstrate that electron transfer between minerals has important implications for Cr(VI) and other high-valence contaminant reduction by Fe(II)-bearing clay minerals in subsurface environments.