粘土矿物中结构铁氧化还原态变化对有机物保存及降解的影响

发布时间：2018-01-06 19:28

本文关键词：粘土矿物中结构铁氧化还原态变化对有机物保存及降解的影响　出处：《中国地质大学(北京)》2017年博士论文　论文类型：学位论文

【摘要】：铁的氧化还原态的变化作为一个重要的地球化学过程,对环境中的元素循环,能量流动,有机质的迁移转化都具有非常深刻的影响。粘土矿物是地表环境中常见的含铁矿物之一,也是与环境中的有机质最紧密结合的矿物类型之一。粘土矿物中的结构铁的氧化还原态的变化对其矿物结构的转化,与有机质结合的状态及对有机质的迁移转化均有着重要影响。通过研究一种模式天然有机质ALA(12-氨基十二酸)与一种富铁的蒙脱石类矿物绿脱石的相互作用,发现ALA可以通过阳离子交换作用插层进入绿脱石的层间域,形成有机粘土复合体。之后我们对比了生物/化学驱动的铁氧化还原作用对这种复合体的影响。结果发现在微生物作用铁还原的初始阶段,铁还原菌的选择性还原机制会优先还原粘土结构边部,及粘土中粒度较小和矿物结晶程度较差的颗粒,并使其发生还原性溶解作用,同时释放出与之结合的ALA,使得在这个还原的阶段过程中铁的还原程度与ALA的释放量呈现正相关关系(还原程度12%)。在后续的生物还原阶段(还原程度12~30%)及接下来的空气再氧化阶段ALA则不再继续释放。这说明ALA的释放主要来自于粘土边部及结晶程度较差的颗粒。与生物还原作用不同,化学还原不表现出任何的选择性,并且在还原过程中由于较多的矿物溶解作用会使得大量与之结合的ALA从粘土层间释放。但是由于自然环境中微生物是主导铁氧化还原循环的主要媒介,该结果证明粘土的层间域是保存有机质的潜在有效场所另一方面我们发现含铁粘土矿物中的结构Fe(II)在氧化条件下可以在无光,中性pH的条件下通过催化氧气产生大量的羟基自由基(·OH)。产生的·OH由于其极强的氧化性可以有效地降解一种新兴污染物,1,4-二恶烷。1,4-二恶烷的降解与·OH的产量,Fe(II)的氧化量均成线性相关关系,其主要的降解产物为甲酸。不同的粘土矿物类型,初始Fe(II)浓度,以及阴离子缓冲液的成分均会影响·OH的产生效率及1,4-二恶烷的降解效率。其中,绿脱石被证明是一种可以有效地循环利用产生·OH及降解1,4-二恶烷的矿物材料。通过生物及化学的方式都可以对其中的结构铁进行循环再生。该结果证明了含铁粘土矿物在氧化还原变化的环境中可以产生大量的·OH,能够有效地降解游离态的有机物/有机污染物如1,4-二恶烷,可以作为一种有潜力的原位环境治理材料,同时也对环境中有机质的迁移转化有重要启示。
[Abstract]:As an important geochemical process, the change of redox state of iron plays an important role in the circulation and energy flow of elements in the environment. The migration and transformation of organic matter have a profound influence. Clay minerals are one of the common iron-bearing minerals in the surface environment. It is also one of the most closely associated mineral types with organic matter in the environment. The change of redox state of structural iron in clay minerals transforms its mineral structure. The combination state with organic matter and its effect on the migration and transformation of organic matter were studied. A model of natural organic matter, ALA-12- amino 12 acid, was studied. The interaction with an iron-rich montmorillonite mineral called green demineralization. It is found that ALA can intercalate into the interlaminar domain of green demineralization through cation exchange interaction. The organic clay complex was formed. Then we compared the effect of biochemically driven iron redox on the complex. It was found that in the initial stage of microbial iron reduction. The selective reduction mechanism of iron reducing bacteria will give priority to the reduction of clay structure edge, and the smaller particle size and lower crystallinity of minerals in the clay, and make it dissolve reductively. At the same time release the combined ALA. The degree of iron reduction is positively correlated with the amount of ALA released in this stage of reduction (12% of reduction degree). In the subsequent stage of biological reduction (1230% of reduction degree), there is a positive correlation between the degree of iron reduction and the amount of ALA released. The release of ALA was mainly from the edge of clay and the less crystallized particles, which was different from the biological reduction. Chemical reduction does not exhibit any selectivity. And in the process of reduction, because of more mineral dissolution, a large amount of combined ALA can be released from the clay layer. However, because of the natural environment, microorganisms are the main medium leading the iron redox cycle. The results show that the interlaminar domain of clay is a potential effective place for the preservation of organic matter. On the other hand, we find that the structure FeIIs in ferric clay minerals can be oxidized without light. Under neutral pH conditions, a large amount of hydroxyl radical (路OH) is produced by catalyzing oxygen. The resulting 路OH can effectively degrade a new pollutant, 1,4-dioxane, because of its strong oxidizing properties. The degradation of 4- dioxane is linearly correlated with the oxidation amount of 路OH yield. The main degradation product is formic acid. Different types of clay minerals and initial Fe2 concentration are the main degradation products. And the composition of anion buffer will affect the production efficiency of 路OH and the degradation efficiency of 1-dioxane, among which, the green demineralization has been proved to be an effective way to recycle the production of 路OH and degradation of 1. Mineral materials of 4-dioxane. The structural iron in it can be regenerated biologically and chemically. The results show that the iron-containing clay minerals can produce a large amount of 路O in the redox environment. H. Organic compounds / organic pollutants, such as 1o 4- dioxane, can be used as potential in situ environmental treatment materials, and also have important implications for the migration and transformation of organic matter in the environment.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P59;P578.6

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