https://scholars.lib.ntu.edu.tw/handle/123456789/77086
標題: | 金屬陽離子在二氧化矽/水溶液固液界面反應之研究 Interaction of metallic cations between the inter face of SiO2(s)/solution |
作者: | 駱尚廉 | 關鍵字: | 二氧化矽;三價鋁;三價鐵;表 面反應;穿透式顯微鏡;電泳;SiO2;Al(III);Fe(III);Surface reactions;TEM;Electrophoresis | 公開日期: | 31-七月-2000 | 出版社: | 臺北市:國立臺灣大學環境工程學研究所 | 摘要: | 不論在自然界之河川、湖泊水體、底 泥,或在污泥堆置、廢棄物掩埋場之土壤、 地下水層中,金屬陽離子之傳輸與流佈均 是環境工程所關切之問題。惟其行為常受 周遭固相介質之影響,而在固/液界面發生 吸附、水解、表面沈澱等反應。事實上, 從吸附到水解以至於表面沈澱應是一個連 續的過程。金屬陽離子會隨著液相濃度、 pH 值以及反應時間之提高,而在固相表面 發生吸附、水解最後形成表面新沈澱固相 之反應。二氧化矽是地殼中含量最豐富的 礦物也是此工業上廣泛應用的基材,故本 研究將以二氧化矽為固相氧化物,探討三 價鋁及三價鐵兩種金屬陽離子於不同系 統pH 值、不同金屬陽離子濃度下,在其表 面與水溶液間之反應。 穿透式電子顯微鏡觀察結果顯示純二 氧化矽系統之顆粒會聚集在一起。三價鐵/ 二氧化矽系統會有不連續的氫氧化鐵固體 物出現在液相中。三價鋁/二氧化矽系統不 論在高的系統pH 值下,其金屬氫氧化物固 體會在原二氧化矽表面開始成長。 在電泳動實驗顯示,當二氧化矽表面吸 附/沈澱金屬陽離子時表面電性會發生改 變。亦即系統有三次的電性逆轉點。當表 面還未吸附金屬陽離子時,呈現原二氧化 矽之特性,即電性逆轉點1;電性逆轉點2 表示開始發生表面沈澱現象;電性逆轉點 3 則為金屬陽離子氫氧化物固體之等電點 值。 The transport and fate of metallic cations are issues of concern with regard to the natural environment, such as rivers, lakes, groundwater, and soil in waste disposal sites. When cations exist in an oxide suspension system, it has been proposed that a transition takes place from mononuclear adsorption to hydrolysis to multinuclear adsorption and, finally, to precipitation on the oxide surface or in bulk solution with increasing system pH or cation concentration. SiO2 is the most abundant oxide in the earth crust and can significantly influence a variety of nutrients and pollutants in aquatic and soil environments. Moreover, SiO2 is widely applied to many industrial processes including use as filtration medium in water treatment plants and base substrate in catalysts. Thus, the objectives of this study are to explore the interaction of various metallic cations (Al(III) and Fe(III)) between the interface of SiO2 and aqueous solution. The TEM images show that pure silica particles are aggregate and that the diameter of a primary particle is around 15-25 nm. It is obviously shown from the results that discrete Fe(OH)3 precipitate forms both at low pH (2.40) and at high pH (7.00) around the unchanged size of base SiO2 particle. However, no discrete Al(OH)3 phase is evident in the Al(III)/SiO2 systems. The invisibility of discrete Al(OH)3 precipitate suggests a strong association between Al- (hyro)oxide and the SiO2 surface. With an increasing system pH, the Al(OH)3 precipitate gradually forms on the surface ofthe base SiO2 particle and the particle size becomes larger. The charge reversals (CR) observed in the Al(III)/SiO2 system represent, in order of increasing pH, the point-of-zero charge (PZC) on the SiO2 substrate (CR1), the pH of surface nucleation of Al(OH)3 (CR2), and, at high pH, the PZC of the Al(OH)3 coating (CR3). The observed electrophoresis mobility of Fe(III)/SiO2 is the overall result contributed by negatively charged SiO2 and positively charged Fe(OH)3. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/22048 | 其他識別: | 892211E002018 | Rights: | 國立臺灣大學環境工程學研究所 |
顯示於: | 環境工程學研究所 |
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