水钠锰矿物相转化的实验研究
发布时间：2018-03-30 00:12
本文选题：水钠锰矿 切入点：Shewanella 出处：《南京大学》2017年硕士论文
【摘要】：水钠锰矿是地表环境中最为常见的锰矿物,也是深海沉积物中常见的自生矿物,业已发现水钠锰矿的形成和转变与多种元素的地球化学循环有着密切的关系。锰结核的矿物组成决定了锰结核开发利用的工艺设计,其主要矿物水钠锰矿易随环境变化发生矿物相转变,微生物活动和热流体作用是引发物相转变的重要因素。本文在分析深海锰结核矿物组成和微观结构的基础上,以水钠锰矿还原转化为选题,设计开展了微生物还原和热液反应两个系列的模拟实验,使用多种谱学和微区分析技术,初步探究了两种条件下水钠锰矿发生还原转变的路径和机制。基于模拟实验,研究了水钠锰矿亚种水羟锰矿被异养金属还原细菌Schewanella oneidensis MR-1还原的现象。利用场发射扫描电镜(FESEM)、场发射透射电镜(FETEM)、X-射线衍射光谱(XRD)和激光拉曼分析矿物物相,发现Schewanella oneidensisMR-1还原水羟锰矿可形成纤维状钡镁锰矿、锰的磷酸盐矿物、片状水锰矿和菱猛矿等多种锰价态的矿物,Schewanella oneidensis MR-1细胞与水羟锰矿的直接接触或通过纳米导线的连接的现象较为普遍;死菌组中则以钡镁锰矿和水锰矿为主;而在未接种细菌的培养基条件下,生成三斜水钠锰矿和少量钡镁锰矿等。物相分析和微区观察表明:实验体系的还原程度是决定矿物组成的关键因素。通过模拟实验,对比研究了热液回流条件下六方和三斜水钠锰矿的物相变化。实验结果表明:在热液回流条件下三斜水钠锰矿比六方水钠锰矿更易于发生相变,并且除生成更为平直的纤维状钡镁锰矿外,还观察到板片状的钡镁锰矿纤维聚集体。这一差别与二者矿物晶体结构的差异有关,三斜水钠c姑炭蟮拿萄醢嗣嫣迤阌蒑n(Ⅳ)-O八面体和Mn(Ⅲ)-O八面体按2:1的比例交互排列,其结构与钡镁锰矿的锰氧八面体排布更为相似,因此更易于转化为钡镁锰矿;而六方水钠锰矿结构中往往存在更多的空穴和缺陷,初始粒径更小,形态不规则,在热液回流作用下,六方水钠锰矿优先发生重结晶作用,然后再进行还原转化,因此表现出还原滞后的表观现象。基于上述两组模拟实验揭示的水钠锰矿的还原转化现象,微生物还原作用可将水羟锰矿还原形成多种低价锰矿物,而热液回流处理仅能得到不同形态的钡镁锰矿;不同结构水钠锰矿在热液回流过程中表现出不同的动力学特征,三斜水钠锰矿更易于相变形成结晶形态更好的钡镁锰矿。上述认识不仅有助于理解多种环境条件下水钠锰矿的物相转化行为,还为判识水钠锰矿的微生物转化作用提出了矿物学依据。
[Abstract]:Sodium manganite is the most common manganese mineral in the surface environment, and it is also a common authigenic mineral in deep-sea sediments. It has been found that the formation and transformation of sodium manganese ore is closely related to the geochemical cycle of many elements. The mineral composition of manganese nodules determines the technological design for the development and utilization of manganese nodules. The main mineral, sodium manganite, is prone to change with the change of environment, and microbial activity and thermal fluid action are important factors in the phase transition of the initiator. In this paper, the mineral composition and microstructure of deep-sea manganese nodules are analyzed. Two series of simulation experiments, microbial reduction and hydrothermal reaction, were designed and carried out by using a variety of spectroscopic and microanalysis techniques. The path and mechanism of the reduction transition of sodium manganese ore in water under two conditions are preliminarily explored. The reduction of ferromanganese ore subspecies by heterotrophic metal reductive bacteria Schewanella oneidensis MR-1 was studied. Field emission scanning electron microscopy (SEM), field emission transmission electron microscopy (TEM), field emission transmission electron microscopy (TEM) and laser Raman spectroscopy (LRS) were used to analyze the mineral phases. It is found that Schewanella oneidensisMR-1 can form fibrous barium manganite, manganese phosphate mineral. The phenomena of direct contact with or connection by nanoscale conductors of many kinds of manganese valence minerals Schewanella oneidensis MR-1 cells, such as lamellar manganite and rhombotite, are common, while barium magnesium manganese and manganite are dominant in the dead bacteria group. But under the condition of no bacteria inoculation, the sodium manganite and a small amount of barium manganese ore were formed. The results of phase analysis and microregional observation show that the reduction degree of the experimental system is the key factor to determine the mineral composition. The phase changes of hexagonal and triclinic sodium manganese ores under hydrothermal reflux conditions are compared. The experimental results show that the phase transition of hexagonal sodium manganese ores is easier than that of hexagonal sodium manganese ores under hydrothermal reflux conditions. In addition to the more flat fibrous barium magnesium manganese ore, the lamellar barium magnesium manganese fiber aggregates were observed. This difference is related to the difference of mineral crystal structure between them. The octahedron (鈪，
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