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標題: | 蛭石、蒙特石及伊萊石對一價鉈的吸附與脫附機制 Adsorption and Desorption Mechanisms of Thallium(I) by Vermiculite, Montmorillonite and Illite. |
作者: | Ling-Yi Guo 郭聆亦 |
指導教授: | 王尚禮 |
關鍵字: | 鉈,蛭石,蒙特石,伊萊石,吸附,脫附,XRD,遲滯現象, Thallium,Vermiculite,Montmorillonite,Illite,Adsorption,Desorption,XRD,Sorption-desorption Hysteresis, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 鉈對植物、動物與人類都具有相當高的毒性,其主要污染來源為含鉈礦物冶煉與高科技產業工廠的排放,但目前對土壤中鉈的反應和轉變,以及移動性和有效性仍尚不完全清楚。由於黏土礦物為決定土壤吸附重金屬反應的重要膠體組成之一,探討其對鉈之吸附與脫附機制,將有助於瞭解鉈和土壤之間的交互作用如何決定其有效性和移動性。本研究以蛭石、蒙特石及伊萊石對Tl (I)進行等溫吸附和脫附反應,以探討這些具有不同帶電位置和電荷密度之黏土礦物對Tl (I)的吸附機制。結果顯示,對Tl (I)之吸附量為蛭石>蒙特石>伊萊石;脫附的遲滯現象則為伊萊石>蛭石>蒙特石。伊萊石與蛭石相對於蒙特石有較高的遲滯現象,因此黏土礦物對鉈之吸附作用隨黏土礦物結構之電荷位置和電荷密度而有顯著差異。蛭石和伊萊石的結構主要具有四面體電荷,加以電荷密度較高,因此對鉈之吸附作用力較強,且被固定於蛭石與伊萊石層間的鉈較不易脫附而產生脫附之遲滯現象。而蒙特石之結構主要具有八面體電荷,電荷密度較小且作用距離較遠,因此層間的鉈離子所受到之吸引力較弱,導致吸附可逆性較高,使得脫附遲滯現象較不明顯。研究結果發現,在黏土礦物吸附Tl (I)的過程中,蛭石扮演重要的角色而伊萊石次之,其存在將使得土壤具有固定Tl (I)的作用;蒙特石對Tl (I)的吸附具有高度的可逆性,因此若以蒙特石為土壤黏土礦物之主要組成時,所吸附的Tl(I)較易被脫附,因此具有比較高的移動性。由此研究結果得知,藉由土壤黏土礦物之組成特性可評估汙染地區鉈的移動性及生物可利用性,以及對人體危害的風險。 Thallium (Tl) is highly toxic to living organisms. The major sources of Tl released into the environment are mainly ore mining and high technology industries. So far, the environmental fates of thallium have not been well understood. Clay minerals are one of the important colloid constituents in soils and play an important role in determining the adsorption of metals by soils. Thus, this study investigated the Tl(I) adsorption and desorption mechanisms of 2:1 clay minerals, in hope, to bring insights into the interactions of thallium with soils. The adsorption and desorption experiments of Tl(I) were conducted for vemiculite, montmorillonite, and illite, which have different structural charge properties. The results of adsorption experiment revealed that Tl(I) adsorption capacities of the clay minerals followed the order of vermiculite>montmorillonite>illite. The degree of hysteresis followed the order of illite>vermiculite>montmorillonite. Thus, the adsorption of Tl(I) on clay minerals is significantly influenced by the charge properties of the clay minerals. The negative charges of vermiculite and illite mainly locate at the tetrahedral sites, whereas those of montmorillonite mainly occur at the octahedral site. The location and density of negative charges in the structures of these clay minerals leads to different binding affinities of these clay minerals toward Tl(I) ions. Consequently, these minerals were different in terms of the Tl(I) adsorption capacity and adsorption/desorption hysteresis. As Tl(I) is fixed into the interlayer sites of vermiculite and illite, the adsorbed Tl(I) on these minerals are therefore more difficult to be desorbed. Comparatively, Tl(I) adsorption on montmorillonite is more reversible. Because vermiculite and illite exhibit a high adsorption capacity and a high adsorption irreversibility of Tl(I), the mobility of Tl(I) in the soils containing these two clay minerals is expected to be relatively low due to the strong retention of Tl(I) by these minerals in the soils. Comparatively, when montmorillonite is the predominant clay component of soils, the mobility of Tl(I) in the soils is expected to be relatively high due to the reversible Tl(I) adsorption of montmorillonite in the soils. Therefore, the mobility and bioavailability of Tl(I) in a soils may be determined by the characteristics of clay minerals in the soil, which can be used to assess the risk of Tl(I) pollution to ecosystems and public health. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/73456 |
DOI: | 10.6342/NTU201900712 |
全文授權: | 有償授權 |
顯示於系所單位: | 農業化學系 |
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