Effect of Zn coprecipitation on the structure of layered Mn oxides
Effect of Zn coprecipitation on the structure of layered Mn oxides
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DOI：
10.1016/j.chemgeo.2018.05.044
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发表时间：
2018-08
期刊：
影响因子：
3.9
通讯作者：
Shiliang Zhao;Qian Wang;Jingying Sun;O. Borkiewicz;Rixiang Huang;E. M. Saad;Benjamin P. Fields
中科院分区：
文献类型：
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作者：
Shiliang Zhao;Qian Wang;Jingying Sun;O. Borkiewicz;Rixiang Huang;E. M. Saad;Benjamin P. Fields
锰氧化物(MnOx)是环境中普遍存在的一类金属氧化物，能显著影响金属、营养物质和污染物的生物地球化学循环。由于金属阳离子在广泛的环境条件下具有表面负电荷，因此它们对MnOx具有很强的亲和力，而在MnOx形成过程中或形成之后，金属阳离子的存在可能会显著影响其结构和反应活性。本研究系统地研究了锌离子在矿物形成(即共沉淀)过程中对酸性水钠锰矿和δ-MnO_2结构的影响，这两种合成的类似物在结构上与新鲜的生物氧化锰相似，但结晶度不同。无论是酸性水钠锰矿还是δ-MnO_2，锌离子都以表面吸附形式存在于空位，中断了沿空位的层状堆积，并导致了颗粒横向尺寸的减小。锌离子还降低了δ-MnO2层中的Mn(III)含量，留下了更多的空位(被吸附的锌离子覆盖)。酸性水钠锰矿的层叠减少更为明显，而δ-MnO_2的层状结构改变更为明显。这些结构变化可能会导致天然体系中MnOxin反应性的改变。
Mn oxides (MnOx) are a group of ubiquitous metal oxides in the environment and can significantly affect the biogeochemical cycles of metals, nutrients, and contaminants. Due to their negative surface charge across a wide range of environmental conditions, metal cations have strong affinities for MnOx, and the presence of metal cations during or after the formation of MnOxmight significantly affect their structure and reactivity. This study systematically investigates the effects of Zn2+presence during mineral formation (i.e. coprecipitation) on the structure of acid birnessite and δ-MnO2, two synthetic analogs that are structurally similar to fresh biogenic MnOxbut with different crystallinity. For both acid birnessite and δ-MnO2, Zn2+existed as surface adsorbed species at vacancy sites, interrupted layer stacking alongcaxis, and caused reductions of the lateral particle size. Zn2+also reduced Mn(III) contents in δ-MnO2layers, leaving more vacancy sites (capped by adsorbed Zn2+). The reduction of layer stacking was more obvious for acid birnessite, while the modification of layer structure was more significant for δ-MnO2. These structural changes will likely lead to modified reactivity of MnOxin natural systems.