Ye Li, Liu Wenjing, Shi Qiantao, Jing Chuanyong
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Environ Pollut. 2017 Nov;230:1081-1089. doi: 10.1016/j.envpol.2017.07.074. Epub 2017 Jul 28.
Nanoscale zero-valent iron (nZVI) is an effective arsenic (As) scavenger. However, spent nZVI may pose a higher environmental risk than our initial thought in the presence of As-reducing bacteria. Therefore, our motivation was to explore the As redox transformation and release in spent nZVI waste residue in contact with Pantoea sp. IMH, an arsC gene container adopting the As detoxification pathway. Our incubation results showed that IMH preferentially reduce soluble As(V), not solid-bound As(V), and was innocent in elevating total dissolved As concentrations. μ-XRF and As μ-XANES spectra clearly revealed the heterogeneity and complexity of the inoculated and control samples. Nevertheless, the surface As local coordination was not affected by the presence of IMH as evidenced by similar As-Fe atomic distance (3.32-3.36 Å) and coordination number (1.9) in control and inoculated samples. The Fe XANES results suggested that magnetite in nZVI residue was partly transformed to ferrihydrite, and the IMH activity slowed down the nZVI aging process. IMH distorted Fe local coordination without change its As adsorption capacity as suggested by Mössbauer spectroscopy. Arsenic retention is not inevitably enhanced by in situ formed secondary Fe minerals, but depends on the relative As affinity between the primary and secondary iron minerals.
纳米零价铁（nZVI）是一种有效的砷（As）清除剂。然而，在存在砷还原细菌的情况下，用过的nZVI可能带来比我们最初认为的更高的环境风险。因此，我们的动机是探索与泛菌属IMH（一种采用砷解毒途径的arsC基因载体）接触时，用过的nZVI废渣中砷的氧化还原转化和释放情况。我们的培养结果表明，IMH优先还原可溶性As（V），而非固相结合的As（V），并且在提高总溶解砷浓度方面并无影响。μ-XRF和As μ-XANES光谱清楚地揭示了接种样品和对照样品的异质性和复杂性。然而，对照样品和接种样品中相似的As-Fe原子距离（3.32 - 3.36 Å）和配位数（1.9）表明，IMH的存在并未影响表面砷的局部配位。Fe XANES结果表明，nZVI残渣中的磁铁矿部分转化为水铁矿，并且IMH的活性减缓了nZVI的老化过程。穆斯堡尔光谱表明，IMH使铁的局部配位发生畸变，但并未改变其砷吸附能力。原位形成的次生铁矿物并不会必然增强砷的保留，而是取决于原生和次生铁矿物之间相对的砷亲和力。
