以下水污泥灰合成中孔徑分子篩之表面改質進行水中染料與重金屬吸附研究

Surface modification of mesoporous molecular sieves synthesized from sewage sludge ashes and its application in the adsorption of dyes and heavy metals.

張宇萱(Yu-hsuan Chang)

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(2012年)

摘要

本研究利用鹼熔(alkaline fusion)方法萃取下水污泥灰中矽、鋁源，作為取代合成中孔徑分子篩 A-MCM41 之原料，並與偏矽酸鈉所合成之 Si-MCM41 作結構特性的比較；之後將下水污泥灰所合成之 A-MCM41 以相同的改質方法與條件，將胺基(APTES)、巰基(MPTMS)與乙烯基(TEVS)三種官能基進行表面改質，探討經改質後獲得的 AA-MCM41、MA-MCM41 及 TA-MCM41 之表面鍵結與結構特性之變化；最後利用研究中所合成之五種自製吸附劑進行水中染料及重金屬離子的吸附試驗，探討其吸附成效並建立等溫吸附模式，瞭解以下水污泥灰合成A-MCM41 及其改質功能化後，對於染料與重金屬離子進行吸附去除之可行性。
　　研究結果顯示，以鹼熔之方法確實能將下水污泥灰中的石英相轉變成易溶於水的矽酸鹽類，可有效提供作為合成 A-MCM41 之矽、鋁源。A-MCM41 合成後之 XRD 晶相鑑定，具有主繞射峰(100)及兩副波峰(110)及(200)之顯現；在結構特性方面，A-MCM41 的比表面積為 805 m2/g，孔體積為 0.81 cm3/g，而偏矽酸鈉所合成之 Si-MCM41 之比表面積為 1025 m2/g ，孔體積為 1.04 cm3/g。以 FTIR 鑑定
A-MCM41 表面化學鍵結，在吸收帶 1079 cm-1 及 1269 cm-1 兩處代表結構中確實具有 MCM-41 主要之 Si-O-Si 鍵結，且藉由鍛燒之方式可有效將界面活性劑去除。由27Al NMR圖譜可發現在 53 ppm 時有波峰(peak)的產生，證實鋁原子以鋁氧四面體的形式進入A-MCM41 的骨架當中。在表面改質的結果顯示，改質後之AA-MCM41、MA-MCM41 及 TA-MCM41 仍具有 XRD 晶相鑑定的主繞射峰(100)；改質後之元素組成分析結果，胺基改質之 AA-MCM41 氮(N)含量為 2.69
mmol/g；以巰基改質之 MA-MCM41 硫(S)含量為 1.74 mmol/g；而由乙烯基所改質的TA-MCM41 碳(C)含量為 5.47 mmol/g；在 FTIR 分析之結果，各官能基所代表之特徵鍵結皆有顯現，表示本研究之改質方法確實能將有基官能基以後嫁接(post-grafting)的方式達到改質之效果。
　　在染料與重金屬離子吸附試驗方面，接觸時間以 24 小時為最適之吸附平衡時間；單成份吸附試驗中去除率之比較，以比表面積為 805 m2/g之A-MCM41對亞甲基藍(MB)的去除率為最佳(87.03 %)，而 Pb(II)與 Cu(II)則以胺基改質後之AA-MCM41 具有最優異之去除率(分別為 99.91 %與 58.99 %)；在多成份系統中，亞甲基藍(MB)的吸附量下降幅度最大(32.76 %-76.39 %)，其次為Pb(II)(9.31
%-65.77 %)，而 Cu(II)的下降幅度最小(3.48 %-55.32 %)，表示當多種污染物同時存在時，確實會產生競爭吸附之情形。而將吸附效果表現最理想的 A-MCM41、AA-MCM41 及 MA-MCM41 三者建立等溫吸附曲線，由結果之各項參數與 R2 值之判斷(R2=0.9959-0.9999)，三者對 MB、Pb(II)與 Cu(II)重金屬離子皆屬於 Langmuir等溫吸附模，A-MCM41 與 MA-MCM41 對 MB 之吸附量最大，分別可達 0.49 mmol/g 與 0.27 mmol/g；AA-MCM41 對 Pb(II)、Cu(II)離子的吸附量分別為 0.71 mmol/g 與 1.25 mmol/g。

關鍵字

重金屬離子 ； 染料 ； 表面改質 ； 下水污泥灰 ； 中孔徑分子篩

並列摘要

In　this study the feasibility of synthesizing mesoporous molecular sieve (i.e., referred to as A-MCM41) by using sewage sludge ash (SSA) as the starting Si and Al sources ; and the enhanced adsorption of heavy metals (Pb and Cu) and organic dye (methylene blue) by the resultant A-MCM41 was investigated with surface modification　by　three　modifiers　(3-aminopropyltriethoxysilane,　3-Mercaptopropyl-trimethoxysilane, and Triethoxyvinylsilane.)
　　For the preparation of a precursor solution for subsequent MCM41 synthesis, Si was solubilized from sewage sludge ash (SSA) by alkali fusion process with a 1.25 NaOH (s) /SSA (by weight) ratio at 400 ℃, followed by a extraction with deionized
water at a L/S=7. It was confirmed that quartz had converted into soluble sodium silicate (Na2SiO3) and sodium aluminum (Na4Al2Si2O9) during the fusion process. The target MCM-41 was synthesized by a hydrothermal process at 105 ℃, using the precursor solution, ammonium hydroxide, and C16TAB (Cetyltrimethylammonium bromide, as surfactant). After the synthesis process, the resultant products were filtered
and calcined at 550 ℃ to remove the surfactant and the A-MCM41 was formed. However, due the presence of Al 2 O 3 derived from SSA, the extracted Al species from SSA was found to be tetrahedrally incorporated in the framework (i.e., A-MCM41), as confirmed by the 27Al NMR analysis. Moreover, the optimum A-MCM41 as synthesized from SSA in this study had a surface of 805 m
2/g and a pore volume of 0.81 cm3/g, as compared to 1025 m2/g　and　1.04 cm3/g, respectively, of　the control
sample synthesized from pure Na2SiO3.
　　Finally,　the　surface　of　A-MCM41　as　synthesized was　further　modified　with　3-aminopropyltriethoxysilane (APTES),　(3-Mercaptopropyl)-trimethoxysilane　(MPTMS) and Triethoxyvinylsilane (TEVS), bonding functional groups to the surface　to　functionalize　the　mesoporous　materials　(i.e.,　referred　to　as　AA-MCM41,　MA-MCM41　and TA-MCM41, respectively). The functionalized A-MCM41s were
characterized by FT-IR and EA technologies. The small angle XRD pattern indicates　that the structure of AA-MCM41,　MA-MCM41　and　TA-MCM41　retain　the　characteristic peaks of A-MCM41.
　　Five MCM-41s, including three surface modified A-MCM41s, as well as the A-MCM41 as synthesized, and the pure Si-MCM41 were evaluated for their adsorption performance in Pb(II), Cu(II) and MB. For heavy metals adoption, the amino-functionalized AA-MCM41 was found to have a better removal efficiency for
Pb(II) and Cu(II) (i.e., 99.96 % and 58.99 %, respectively in a single component system with initial concentration 100 mg/L); whereas for organic dye　adsorption, the A-MCM41 as synthesized from SSA was found to have greater removal efficiency for MB (i.e.,87.03 %.). The adsorption of Pb(II), Cu(II) and MB, in a multi-component system showed decreased adsorption quantity for the tested adsorbates, possibly due to the competition among the adsorbates. It was also found that the selectivity for the tested adsorbates in decreasing order was Cu(II)>Pb(II)>MB. In the adsorption isotherm, A-MCM41, AA-MCM41 and MA-MCM41 were found well fitted with the Langmuir model (R2=0.9959-0.9999). The maximum adsorption of MB was found to be 0.49 mmol/g for A-MCM41; and the maximum adsorption of Pb(II) and Cu(II) was 0.71mmol/g and 1.25 mmol/g, respectively for AA-MCM41.
　　This work demonstrated that it is feasible and beneficial to synthesize A-MCM41 with SSA as starting silicon and aluminum sources was effective in organic dye and metal ion adsorption. And for this synthesis technology suggesting that the preparation of A-MCM41 with SSA could contribute to the recycling of sewage sludge and is feasible, effective, and environmental beneficial.

並列關鍵字

organic dye ； sewage sludge ash ； MCM-41 ； function group ； heavy metal ions

參考文獻

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