||Preparation of oxidized/porous electrospun carbon nanofibers and their use as adsorbents for copper ions
||Department of Chemical Engineering
以純硝酸溶液及硫酸/硝酸混合溶液對碳纖維進行改質。經過強酸改質過後，奈米碳纖維仍然保有完整的纖維狀，纖維的表面並沒有明顯變化，表示酸性改質並沒有破壞纖維原有的型態。經過氧化改質之奈米碳纖維，含有大量含氧官能基，由疏水性材料轉變為親水性材料，使得銅離子能夠更加容易地克服纖維表面與水溶液之界面阻力，能夠有效與銅離子產生作用而達到吸附的效果。在吸附動力學方面，碳纖維無論改質與否，皆較符合擬二階動力學方程式，代表著吸附動力學的決定步驟取決於碳纖維與銅離子之間的交互作用力。而等溫吸附模型中，經氧化改質之奈米碳纖維皆較符合Langmuir model，經由此模型計算可得純硝酸、硫酸/硝酸改質碳纖維之最大吸附量分別為 78.7及169.5 mg/g。硫酸/硝酸改質之碳纖維有較好之吸附效果，其原因可能在於C=O相較於C-OH對銅離子有更好的吸引力，因為碳纖維本體存在著大量芳香烃結構，因此能夠與C=O透過π-π電子轉移而對銅離子有較好之吸引力。
本研究亦以polymethylmethacrylate/polyacrylonitrile (PMMA/PAN) 為前驅物製備多孔性奈米碳纖維，隨PMMA添加量上升表面積明顯增大，且產生大量孔洞，但在銅離子的吸附效果上並沒有太過突出的表現，其原因為所產生之孔洞多為中孔，與銅離子大小差異過大，導致無法有效地提升吸附量。
In this study, we prepared electrospun carbon nanofibers with different carbonization temperatures and oxidation modified manners for the use as copper ion adsorption material. When the carbonization temperature was 1300 °C, pores were closed during the growth of carbon plane, resulting in a decrease in the specific surface area and pore volume. Furthermore, most of the functional groups were removed and fibers became hydrophobic, which resulted in the poor adsorption efficiency of copper ions.
We further modified carbon nanofibers with pure nitric acid and sulfuric acid/nitric acid. After acid modification, oxygen-containing functional groups increased considerably and fibers changed from hydrophobic to hydrophilic. In terms of adsorption kinetics, the adsorption behavior of carbon nanofibers agreed well with the pseudo-second-order equation. In the adsorption isotherm, the oxidized carbon nanofibers agreed with Langmuir model. The obtained maximum amount of adsorption of nitric acid and sulfuric acid/nitric acid modified carbon nanofibers were 78.7 and 169.5 mg/g, respectively.
We also prepared porous carbon nanofibers by electrospinning of poly(methylmethacrylate)/PAN solutions. When the amount of PMMA increased, the surface area and pore volume increased significantly. However, the adsorption of copper ions only showed a slight increase. This was attributed to the large pore size for copper ions, making it impossible for adsorption.
Extended Abstract II
第一章 緒論 1
1.1 前言 1
第二章 文獻回顧 3
2.1 電紡絲技術 3
2.1.1 電紡絲原理 3
2.1.2 電紡絲製程之參數 5
2.2 孔洞纖維的製備 12
2.2.1 相分離法 13
2.2.2 高溫分解法 13
2.2.3 控制濕度產生孔洞 14
2.3 PAN奈米碳纖維熱處理 15
2.4 吸附機制 17
2.4.1 原理 17
2.4.2 物理吸附 18
2.4.3 化學吸附 18
2.5 吸附過程 19
2.5.1 影響吸附之因素 19
2.6 等溫吸附模式 21
2.6.1 Langmuir Isotherm[31-34] 21
2.6.2 Freundlich Isotherm 22
2.7 電紡絲纖維應用於重金屬吸附 23
2.8 研究動機與目的 32
第三章 實驗方法與步驟 33
3.1 實驗藥品 33
3.2 實驗儀器 34
3.3 實驗方法 37
3.3.1 奈米碳纖維之實驗流程 37
3.3.2 硝酸改質奈米碳纖維之實驗流程 40
3.3.3 硫酸/硝酸改質奈米碳纖維之實驗流程 42
3.3.4 PMMA/PAN多孔性奈米碳纖維之實驗流程 44
第四章 結果與討論 46
4.1 奈米碳纖維 46
4.1.1 奈米碳纖維之型態 46
4.1.2 奈米碳纖維之結構判定 49
4.1.3 奈米碳纖維之官能基鑑定 53
4.1.4 銅離子吸附之研究 57
4.2 硝酸改質奈米碳纖維 65
4.2.1 硝酸改質奈米碳纖維之型態 65
4.2.2 硝酸改質奈米碳纖維之結構判定 69
4.2.3 硝酸改質奈米碳纖維之官能基鑑定 72
4.2.4 銅離子吸附之研究 75
4.3 硫酸/硝酸改質奈米碳纖維 82
4.3.1 硫酸/硝酸改質奈米碳纖維之型態 82
4.3.2 硫酸/硝酸改質奈米碳纖維之結構判定 86
4.3.3 硫酸/硝酸改質奈米碳纖維之官能基鑑定 89
4.3.4 銅離子吸附之研究 92
4.4 PMMA/PAN 多孔性奈米碳纖維 99
4.4.1 多孔性奈米碳纖維形成之機制 99
4.4.2 多孔性奈米碳纖維之型態 100
4.4.3 多孔性奈米碳纖維之結構判定 106
4.4.4 銅離子吸附之研究 109
第五章 結論 120
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