粘土矿物吸附镉性能及缓解狐尾藻镉毒害效应研究

发布时间：2019-03-20 07:30

【摘要】：海泡石和蒙脱石是两类典型的粘土矿物,有良好的吸附性能,且成本低、储量丰富和环境友好,因此在重金属污染控制领域有良好的应用前景,相关的研究工作也得到了广泛关注。近年来,利用粘土矿物对重金属的吸附、配合、共沉淀等作用来降低重金属在环境中的迁移性和生物有效性成为了研究热点,粘土矿物在缓解重金属对植物毒害作用方面极具应用前景。另一方面,不同粘土矿物由于表面活性官能团种类和数量的不同,对重金属离子的吸附性能和机制存在较大差异,其缓解植物毒害能力也可能不同,尤其是在实际环境中多种离子共存的条件下的缓毒能力;但相关研究工作目前还鲜有报道。因此,有必要深入研究粘土矿物表面结构和共存离子对重金属吸附行为的影响,并进一步考察其对缓解水生植物重金属毒害作用的影响。本文以天然海泡石和蒙脱石为粘土矿物代表,对比研究共存阳离子(Ca~(2+)、K~+、Na~+)和阴离子(H_2PO_4~-、SO_4~(2-)、NO_3~-)对其吸附Cd~(2+)的影响,分析其吸附性能及机制的差异性。在此基础上,比较两种粘土矿物存在条件下,不同浓度Cd~(2+)胁迫下狐尾藻生物量、叶绿素、可溶性蛋白以及丙二醛的影响,探究粘土矿物吸附特征对其缓解狐尾藻镉毒害效应的相关机制。研究工作主要得到了以下结论:(1)采用X射线衍射、X荧光光谱、红外光谱、热重分析等结构表征手段,研究了所选天然海泡石和蒙脱石的结构特征,结果表明:海泡石和蒙脱石具有相似的化学组成成分,在热分析中海泡石主要脱除的是结构内的羟基水,占总失重的71.6%,而蒙脱石主要脱去的是表面吸附水以及孔隙水,占总失重的90.9%;结合红外光谱分析,表明海泡石的结构中含有大量的结构羟基(Si-OH、Mg-OH)。(2)揭示了蒙脱石和海泡石对Cd~(2+)吸附特征具有显著差异性的相关机制。在纯水体系中,蒙脱石对Cd~(2+)的吸附效果优于海泡石,但是在营养液复合体系中海泡石对Cd~(2+)的吸附效果却要比蒙脱石好。这是因为共存阳离子和含氧酸根阴离子均能强烈抑制蒙脱石对Cd~(2+)的吸附,而对于海泡石,虽然阳离子和NO_3~-的存在同样不利于Cd~(2+)的吸附,但是H_2PO_4~-、SO_4~(2-)却能与海泡石结构中的Si-OH和Mg-OH发生配体交换,为Cd~(2+)提供新的吸附位点形成三元络合物,促进Cd~(2+)吸附。(3)发现海泡石和蒙脱石均能缓解Cd~(2+)对水生植物狐尾藻的毒害效应,建立了吸附Cd~(2+)特征与缓解其毒害效应之间的对应关系。减轻Cd~(2+)对叶绿体结构的破坏,降低植物的膜质过氧化反应,有利于水生植物的生长。由于结构及吸附原理的差异性,海泡石在多种离子共存的条件下,对重金属的吸附更占优势,所以缓解毒害效应的效果要比蒙脱石更显著。
[Abstract]:Sepiolite and montmorillonite are two typical clay minerals, which have good adsorption properties, low cost, abundant reserves and friendly environment, so they have good application prospects in the field of heavy metal pollution control. The related research work has been paid more and more attention. In recent years, the use of clay minerals for heavy metal adsorption, coordination, coprecipitation and other actions to reduce the migration and bioavailability of heavy metals in the environment has become a hot research topic. Clay minerals have great application prospects in alleviating the toxicity of heavy metals to plants. On the other hand, due to the different types and quantities of surfactant functional groups, the adsorption properties and mechanisms of different clay minerals to heavy metal ions vary greatly, and their ability to alleviate plant toxicity may also be different. Especially in the real environment under the co-existence of a variety of ions under the conditions of the anti-virus ability; However, the relevant research work is still rarely reported. Therefore, it is necessary to study the surface structure of clay minerals and the influence of co-existing ions on the adsorption behavior of heavy metals, and to further investigate their effects on alleviating the toxicity of heavy metals in aquatic plants. Using natural sepiolite and montmorillonite as clay minerals, the effects of co-existing cations (Ca~ (2), K ~, Na~) and anions (H _ 2O _ 2PO _ 4 ~ (2 -), so _ (2 -) ~ (2 -), NO_3~-) on their adsorption of Cd~ (2) were studied. The difference of adsorption performance and mechanism was analyzed. On this basis, the effects of different concentrations of Cd~ (2) on biomass, chlorophyll, soluble protein and malondialdehyde were compared in the presence of two kinds of clay minerals. To explore the mechanism of clay mineral adsorption to alleviate cadmium toxicity of Foxtail algae. The main conclusions are as follows: (1) the structural characteristics of selected natural sepiolite and montmorillonite were studied by means of X-ray diffraction, X-ray fluorescence spectroscopy, infrared spectroscopy and thermogravimetric analysis. The results show that sepiolite and montmorillonite have similar chemical composition. In thermal analysis, the main removal of sepiolite is hydroxyl water in the structure, accounting for 71.6% of the total weight loss, while montmorillonite is mainly removed from the surface adsorbed water and pore water. 90.9% of total weightlessness; The structure of sepiolite contains a large number of structural hydroxyl groups (Si-OH,Mg-OH). (2), which indicates that the adsorption characteristics of Cd~ (2) on montmorillonite and sepiolite are significantly different from those of sepiolite. In pure water system, the adsorption effect of montmorillonite on Cd~ (2) is better than that of sepiolite, but it is better than that of montmorillonite in the compound system of nutrient solution for Cd~ (2). This is because both co-existing cations and oxygen-containing anions can strongly inhibit the adsorption of Cd~ (2) on montmorillonite, while for sepiolite, although the presence of cations and NO_3~- is not conducive to the adsorption of Cd~ (2), the adsorption of Cd~ (2) is strongly inhibited by the presence of cations and oxygen-containing anions. However, SO_4~ (2 -) can exchange ligands with Si-OH and Mg-OH in sepiolite structure, which provides a new adsorption site for Cd~ (2) to form ternary complex. The adsorption of Cd~ (2) was promoted. (3) it was found that both sepiolite and montmorillonite could alleviate the toxic effect of Cd~ (2) on aquatic plants, and the corresponding relationship between the characteristics of Cd~ (2) adsorption and its toxic effect was established. It can reduce the damage of chloroplast structure caused by Cd~ (2) and decrease the membrane peroxidation of plants, which is beneficial to the growth of aquatic plants. Due to the difference of structure and adsorption principle, sepiolite is more dominant for heavy metal adsorption in the presence of a variety of ions, so the effect of relieving toxicity is more obvious than that of montmorillonite.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X173;X505

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