下水污泥灰衍生之矽鋁含量對合成 Al-MCM-41 結構之影響

Characterization of Al-MCM-41 and its modification synthesized from sewage sludge ash

陳虹屹(Hung-yi Chen)

指導教授 ： 王鯤生

國立中央大學/工學院/環境工程研究所/碩士(2011年)

摘要

本研究利用下水污泥灰當中矽鋁元素做為合成Al-MCM-41之材料，並將污泥灰進行酸處理程序，使用鹼熔法萃取元素矽鋁，改變前驅液當中去離子水添加比例，以探討同時自污泥中萃取出的鋁原子對於Al-MCM-41結構的影響，再將自行合成之Al-MCM-41以後嫁接法進行胺基官能基改質，探討經改質後對於分子篩材料特性之影響。實驗結果發現利用NaOH:ash=1.25:1比例，在400℃下鹼熔可將難溶於水石英相轉變為較易溶於水之矽酸鹽、矽鋁酸鹽相。利用去離子水不同添加比例（L/S=3、7、15、50）萃取之前驅液，主要元素為Si、Al、Fe、Na。未經酸處理之下水污泥灰在液固比3時有最大矽鋁萃取率，矽34.81%、鋁7.78%，四組液固比下矽鋁比最低為13.98，最高僅18.03；經酸處理下水污泥灰矽鋁比範圍由11.89升高至62.88，在液固比3具最大矽萃取率79.14%及鋁最大萃取率37.59%；當液固比升高時，由於NaOH濃度降低、溶液鹼度下降，酸處理污泥灰萃取率因而減少。未經酸處理污泥灰中之二氧化矽佔57.35%，經酸處理程序可將原料當中之鋁、鐵等元素含量降低，提高二氧化矽在污泥灰當中之比例71.43%，但同時會造成鹼熔過後各元素前驅液萃取率上升之現象。在水熱合成Al-MCM-41方面，由X光繞射分析圖譜、化學成分分析、穿透式電子顯微鏡及氮氣吸脫附曲線分析等證明各種條件下皆成功合成分子篩；Al-MCM-41材料中主要成分為Si，Al元素其次；未經酸處理Al-MCM-41產物矽鋁比隨液固比升高而降低，液固比3時產物矽鋁比20.50，液固比50之矽鋁比為7.89；經酸處理Al-MCM-41矽鋁比趨勢相反，液固比3產物矽鋁比為16.89，液固比50矽鋁比39.36；未酸處理及酸處理兩者之Al-MCM-41在矽鋁比各為最大（20.50、39.36）時，具有較大的表面積699.15 m2/g、1057.95 m2/g，且產物之孔徑較小，分別為3.43 nm、3.81 nm，結果說明矽鋁比大可得性質較優良之分子篩材料；FTIR圖譜在960-970 cm-1出現Si-O-Al波峰，證明Al存在Al-MCM-41中；分析改質後Al-MCM-41依舊具有MCM-41特徵波峰；27Al 核磁共振分析方面，除未酸處理液固比50具有一小型八面體鋁波峰（Oh）外，其餘材料在改質後只有一個53±2ppm的波峰（Td）；FTIR中，O-H官能基的3431.75 cm-1吸收帶與未改質前相比顯得更平緩，與未改質前之材料相比，改質後在714、1560 cm-1吸收帶有波峰產生，顯示O-H官能基在改質後被胺基官能基所取代，也證實自行合成之Al-MCM-41材料表面確實具有胺基官能基。

關鍵字

Al-MCM-41 ； 酸處理程序 ； 下水污泥灰 ； 鹼熔萃取法

並列摘要

This study investigated the feasibility of synthesizing Al-MCM-41 with silicon and aluminum sources that were extracted by alkaline fusion process from sewage sludge ash (SSA). The synthesized and the further surface-modified Al-MCM-41s were characterized, and the adsorption performance was evaluated.
Two types of sewage sludge ash (SSA) as received, and SSA treated with acid, were tested in this study. The results indicate that starting with an alkaline fusion treatment of the SSA (mixed with NaOH by 1:1.25 weight ratio) at 400℃, it rendered the quartz soluble for extraction by forming sodium silicate (Na2SiO3) and sodium aluminum silicate (Na4Al2Si2O9).
After this fusion treatment, silica and aluminum were extracted from the fused solid with deionized water at various tested L/S ratios (i.e., liquid to solid ratio), ranging from 3,7,15 to 50. It was noted that acid-treated SSA showed increased efficiency in Al and Si extraction as compared to the SSA as received. Both the tested SSAs showed the greatest extraction efficiency at L/S=3, and then the extraction efficiencies decreased with increasing L/S ratios. Maximum extraction efficiencies for Si and Al were found to be 34.81 wt% and 7.78 wt%, respectively, for SSA without acid treatment, as compared to those of 79.17 wt% and 37.59 wt% for acid-treated SSA.
The Al-MCM-41 was synthesized by hydrothermal process at 105℃, in the presence of the precursor solution (i.e., as prepared by the above extraction process), ammonium hydroxide, and C16TAB (Cetyltrimethylammonium bromide, as surfactant). After the completion of hydrothermal process, the target products were filtered from the solution and then calcined at 550℃ to remove the surfactant, this resulting in Al-MCM-41 products. However, due to the presence of SSA-derived Al2O3, the Al-MCM-41 thus synthesized incorporated Al into its structure (i.e., referred to as Al-MCM-41), and was reported to have
enhanced the stability of the Al-MCM-41 structure. The composition of Al-MCM-41 as prepared from original SSA was found to contain 86.89-93.21% Si, 3.86-9.58% Al, and trace of other elements, with a 761.65 m2/g surface area, and 0.85 cm3/g pore volume. In contrast, the Al-MCM-41 as prepared from the acid-treated SSA showed a greater surface area of 1057.95 m2/g, and a pore volume of 1.02 cm3/g. For the acid-treated SSA, the extraction efficiencies of Si and Al varied with L/S ratio. This resulted in a wide range of Si/Al ratio in the precursor solutions (i.e.,11.89-62.88) and in the resultant Al-MCM-41
products (i.e., 16.89-39.36). The Al-MCM-41 prepared at higher Si/Al ratio seemed to have better sieve properties (i.e., larger surface area and pore volume.)
Finally, the surface of Al-MCM-41 as synthesized was further modified with 3-aminopropyltriethoxysilane(APTES) to bond ammoniums-functional groups. The surface-modified Al-MCM-41, referred to as ammonium-functionalized mesoporous materials (AFMM), were proved to enhance the adsorption capability of mesoporous sieves.The AFMM was characterized by FT-IR, XRD, TEM and SEM techniques, and BET analysis. The XRD pattern indicated that the structure of AFMM retained the characteristic peaks of MCM-41; and further the FT-IR confirmed the functional groups of -NH2 and N-H around 714 and 1560 cm-1.
This study demonstrated that it is feasible to synthesize Al-MCM-41 using silicon and aluminum sources extracted from sewage sludge ash. An acid-pretreatment of the SSA
would enhance the extraction efficiencies of Si and Al, this resulting in the synthesis of Al-MCM-41, with larger surface area and pore volume. The results may contribute to the recycling of sewage sludge and the production of a green functionalized mesoporous material.

並列關鍵字

sewage sludge ash ； alkaline fusion ； acid-washing process ； Al-MCM-41

參考文獻

[60]周書賢，「合成及鑑定高水熱穩定性中孔分子篩MCM-41」，私立中原大學化學研究所，碩士論文，2003。

[64]黃子光，「下水污泥灰合成中孔徑分子篩及表面改質吸附重金屬之研究」，國立中央大學環境工程研究所，碩士論文，2010。

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