抗污塞性及高穩定性聚乙二醇共聚高分子塗布PVDF薄膜之廢水處理應用與界面作用力分析

本研究中，以苯乙烯（styrene）以及聚(乙二醇)甲醚甲基丙烯酸酯（poly(ethylene glycol) methyl ether methacrylate, PEGMA）進行聚合反應，合成出具有抗污塞能力之共聚高分子（polystyrene-block-PEGMA, PS-b-PEGMA），藉由物理性塗布的方式，將其吸附於疏水性聚偏二氟乙烯（polyvinylidene fluoride, PVDF）微過濾薄膜上，並探討共聚高分子之親疏水端鏈長比例與分子量大小，對抗污塞性與穩定性之影響。研究結果指出，PS疏水性鏈段的增長，可有助塗布密度及穩定性的增加，但過長的PS鏈段則會影響抗蛋白吸附的能力。雖然PEGMA有助於抵抗蛋白的吸附，但PEGMA鏈段過長時，高分子間受空間障礙的影響，導致塗布密度會於隨PEGMA鏈長增加而下降，反而讓蛋白質能穿透到分子間的空隙，造成蛋白吸附量的上升。最適化之PS55-b-PEGMA30共聚高分子塗布於PVDF膜材，能抵抗75%至85%之蛋白吸附和100%的抗菌效果，即使在水溶液中長時間的浸泡（60天）與酸鹼溶液測試下，仍有良好的穩定性及抗蛋白吸附效能。對於MBR之廢水處理試驗中，能以純水清洗來移除膜上的污塞，使其透膜壓力恢復到初始值，具有抗污塞沾黏的能力。故以此塗布方式進行薄膜改質，具有簡便、快速與高效率等優點，並可獲得一高穩定性及抗污塞性之改質膜。在界面作用力分析部分，利用分子模擬來探討有機污塞物之葡聚醣及腐質酸對PVDF與其他兩種氟素材料之聚四氟乙烯（polytetrafluoroethylene, PTFE）和聚氟乙烯（polyvinyl fluoride, PVF）間的作用力分析。由結果發現，不同氟素薄膜之親水程度依序為PVF＞PVDF＞PTFE，與接觸角數據趨勢相符合。其PVF膜材與葡聚醣之間有較高的氫鍵作用力，於膜面上可能有較高的不可逆性污塞比例。此外，由於疏水作用的關係，PVDF薄膜與腐質酸間的作用力較大，而PTFE膜材具有較低的表面能，故對水分子和污塞物的作用力為最低。最後，將PVDF材料與共聚高分子進行親水性比較，顯示出共聚高分子可與水分子產生較多的氫鍵作用力，故可形成一薄水層能抵抗污塞物的沾黏與吸附，與實驗結果一致。

關鍵字

分子模擬；薄膜生物反應器；抗污塞；聚乙二醇；薄膜塗布；作用力

並列摘要

A systematic group of hyper-brush PEGylated diblock copolymers containing poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) was synthesized using an atom transfer radical polymerization (ATRP) method and varying PEGMA lengths. This study demonstrates the anti-biofouling membrane surfaces by self-assembled anchoring PEGylated diblock copolymers of PS-b-PEGMA on the microporous polyvinylidene fluoride (PVDF) membrane. Two types of copolymers are used to modify the PVDF surface, one with different PS/PEGMA molar ratios in a range from 0.3 to 2.7 but the same PS molecular weights (MWs , ~5.7 kDa), the other with different copolymer MWs (~11.4, 19.9, and 34.1 kDa) but the similar PS/PEGMA ratio (~1.70.2). It was found that the adsorption capacities of diblock copolymers on PVDF membranes decreased as molar mass ratios of PS/PEGMA ratio reduced or molecular weights of PS-b-PEGMA increased because of steric hindrance. The increase in styrene content in copolymer enhanced the stability of polymer anchoring on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be in the range between 1.5 and 2.0 with copolymer MWs above 20.0 kDa for the ultra-stable resistance of protein adsorption on the PEGylated PVDF membranes. The PVDF membrane coated with such a diblock copolymer owned excellent biofouling resistance to proteins of BSA and Lysozyme as well as bacterium of E. coli and S. epidermidis, and high stable microfiltration operated with domestic wastewater solution in a membrane bioreactor. For the part of interaction force analysis, a molecular simulation method was used to investigate the interaction between organic foulants and fluoropolymeric membranes, such as humic acid (HA) and dextran interacted with PVDF, polytetrafluoroethylene (PTFE) and polyvinyl fluoride (PVF) materials. The result indicated the hydrophilicity with water molecules followed the order: PVF＞PVDF＞PTFE. The simulated trend was consistent with experimental data of contact angle. Forthurmore, the result of RDF analysis implied that PVF material had more irreversible fouling due to higher interaction of hydrogen-bond with dextran. PVDF material easily attracted with HA because of hydrophobic interaction through energy calculation. PTFE reveal the lowest surface energy to resist water and foulants adsorbed on surface. Finally, the PEGylated copolymer improved hydrophilicity of PVDF membranes to reduce the foulants adsorption because of interaction with water molecules.

並列關鍵字

PEGylated copolymers ； membrane coating ； anti-fouling ； Membrane bioreactor (MBR) ； interaction ； molecular simulation

參考文獻

[1] Wisniewski, C., “Membrane bioreactor for water reuse,” Desalination, 203, 15-19 (2007).

[2] Cote, P., M. Masini and D. Mourato, “Comparison of membrane options for water reuse and reclamation,” Desalination, 167, 1-11 (2004).

[3] Kang, Y. T., H. Chao and E. H. Chung, “Development of the wastewater reclamation and reusing system with a subermerged membrame bioreactor combined bio-filtration,” Desalination, 202, 68-76 (2007).

[4] Visvanathan, C., R. B. Aim and K. Parameshwaran, “Membrane separation bioreactors for wastewater treatment,” Crit. Rev. Environ. Sci. Technol., 30, 1-48 (2000).

[5] Gonzalez, S., M. Prtrovic and D. Barcelo, “Removel of a broad range of surfactants from municipal wastewater－Comparison between membrane bioreactor and conventional activated sludge treatment,” Chemosphere, 67, 335-343 (2007).

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抗污塞性及高穩定性聚乙二醇共聚高分子塗布PVDF薄膜之廢水處理應用與界面作用力分析

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