醋酸纖維素/三醋酸纖維素正滲透薄膜合成與性能

Fabrication and performance of cellulose acetate/cellulose triacetate forward osmosis membrane

謝孟寰(Meng-Huan Hsieh)

指導教授 ： 李篤中

國立臺灣大學/工學院/化學工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201802774

摘要

相較於逆滲透，正滲透技術不需要額外的壓力，可降低不少操作成本，因此近年來廣受眾人研究。然而，由於外部濃度極化以及內部濃度極化的影響，使得正滲透薄膜的水通量遠低於逆滲透，也直接影響其應用領域的廣度。因此本研究以醋酸纖維素/三醋酸纖維素為薄膜的基底，搭配二氧化鈦奈米顆粒以及鋯金屬有機支架進行薄膜改質，提升薄膜的水通量並同時維持低逆向溶質擴散及高離子阻擋率。在二氧化鈦奈米顆粒的改質方面，藉由二氧化鈦在溶液中被吸附在薄膜的高分子上，再與水分子形成氫鍵提高親水性。另一方面，鋯金屬有機支架本身即是親水的材料，直接加入高分子溶液中也可提高親水性。實驗上，先以SEM確認薄膜表面的緻密程度及薄膜厚度，再從接觸角的量測證實薄膜表面親水性的提高。接著再以不同流速測量薄膜的水通量，發現當流速大於50 (毫升/分鐘)時水通量便不再提高，可知此時已可忽略外部濃度極化的影響。同時，以理論數學模型推導出水通量及逆向溶質擴散的式子，搭配實驗數據迴歸作圖求出薄膜的水滲透係數、鹽滲透係數和結構參數。同時求出逆向溶質擴散和水通量的比例，發現經二氧化鈦奈米顆粒改質後的薄膜其比例最好。最後再以鋯金屬有機支架薄膜吸附砷離子，在酸性的環境下可得到較佳的吸附效果。

關鍵字

正滲透 ； 醋酸纖維素 ； 三醋酸纖維素 ； 二氧化鈦 ； 金屬有機支架

並列摘要

Compared to reverse osmosis, external driving force is not necessary for forward osmosis and decrease operating cost. Therefore, forward osmosis becomes a popular research recent years. However, water flux of forward osmosis is much lower than reverse osmosis due to the effect of external concentration polarization (ECP) and internal concentration polarization (ICP). As a result, in this study, CA/CTA membrane with TiO2 nanoparticle and UiO-66 modification are adopted to enhance the water flux, and keep low RSD and high rejection. In terms of TiO2 nanoparticle modification, TiO2 nanoparticle are adsorbed on the membrane, and forms hydrogen bond with water to increase hydrophilicity. On the other hand, UiO-66 is an inherent hydrophilic material and is added into polymer solution directly for hydrophilicity enhancement. In experiment, SEM is used to observe the dense surface of membrane and thickness, then contact angle measurement is used to confirm hydrophilicity enhancement on membrane surface. Afterwards, we observe that when flow rate is larger than 50 (mL/min), water flux maintains a constant. It reveals that the influence of ECP is negligible. Later, derive the formulas of water flux and RSD from theoretical mathematics model, and obtain water permeability, salt permeability and structural parameter by curve fitting. In addition, from the ratio of RSD and water flux, we observe that the membrane with TiO2 nanoparticle modification shows the best performance. Finally, the membrane with UiO-66 modification is used to adsorb arsenate in different pH, and the data shows it can adsorb more arsenate in acidic environment.

並列關鍵字

forward osmosis ； cellulose acetate ； cellulose triacetate ； titanium dioxide ； metal organic framework

參考文獻

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