以TiO2光觸媒進行薄膜表面改質之研究

本研究之目的為利用覆鍍TiO2於薄膜表面，藉此改善腐質酸所造成之通量衰減問題，並透過不同TOC濃度之腐質酸(2及9 mg/L)，不同透膜壓差(70、100及140 kPa)，不同掃流速度(0.22、0.10、0.05 m/sec)，以及兩種薄膜孔徑(0.14 μm、50 kD)等參數所進行之滲透實驗，來觀察操作條件不同對於通量衰減程度、TOC去除率以及膜面上積垢量，這三者分析之影響。在TOC濃度為9 mg/L，透膜壓差為100 kPa，掃流速度為0.22 m/sec的條件下，過濾8小時後，經覆鍍TiO2於陶瓷膜上，其通量僅衰減至39%，相較於無經過膜面改質程序之陶瓷膜，通量則衰減至3%，不過在TOC去除率上卻無法有顯著之效果，而利用質量平衡理論估算出膜面上積垢量有下降之趨勢，證明膜面上之確實能將積垢分解，也因此使分子量較小之腐質酸通過薄膜表面增加滲流液TOC濃度。 0.14 μm薄膜以腐質酸濃度9 mg/L，過濾8小時後，在隨著透膜壓差增加，通量衰減程度越嚴重，這是因為透膜壓差越高，通過薄膜孔隙之腐質酸也隨著增大，而膜面上積垢量也隨之增加，造成通量迅速衰減。掃流速度之快慢，意即代表腐質酸在模組內停留時間之長短，而因此影響膜面上之積垢量，所以掃流速度為0.22 m/sec時，膜面上積垢量為6.32 g/m2，掃流速度為0.10、0.05 m/sec時，膜面上積垢量分別為6.87 g/m2，7.48 g/m2。孔徑越小之薄膜，雖然預期可以攔截更多之腐質酸，但卻在覆鍍TiO2過程中，會有不均勻狀況產生，因此在去除滲流液TOC效果上並不佳。

關鍵字

膜面改質；光催化反應；腐質酸；多孔性二氧化鈦薄膜；延緩通量衰減

並列摘要

Photocatalytic membrane reactors using titanium dioxide immobilized on ceramic membrane were utilized to improve flux decline by humic acid. Different parameters such as TOC concentration (2 and 9 mg/L), transmembrane pressure(70, 100 and 140 kPa), crossflow velocity(0.22, 0.10 and 0.05 m/sec) and pore size(0.14 μm and 50 kD) are used to observe the influences of flux decline, TOC rejection and the amount of foulent on membrane’s surface. After 8 hours ultrafiltration, the flux of porous titanium dioxide membrane decayed to 39% when TOC concentration is 9 mg/L, transmembrane pressure is 100 kPa and crossflow velocity is 0.22 m/sec. Otherwise, the flux of membrane without modification decayed to 3%. On the contrary, the former has no obviously influence on TOC rejection which is considered to be caused by membrane fouling degraded into smaller molecular weight by photocatalytic reaction. The smaller molecule can pass through the membrane, so the TOC concentration increased. The higher transmembrane pressure is used, the more amount of humic acid pass through the membrane. Therefore, the amount of foulent accumulated on membrane surface much more and the permeate flux will decrease relatively. The speed of crossflow velocity means that the retention time of humic acid staying at module. It will result greater influence on membrane’s fouling and permeate flux. In addition, we expected that the smaller pore size of membrane(50 kD) can intercept more humic acid. However it has a drawback of coating uniformly, thus the TOC rejection was not increased.

並列關鍵字

Membrane modification ； Photocatalysis ； Humic acid ； Porous titanium dioxide membrane ； Improve flux decline

參考文獻

Arabatzis, I.M., Antonaraki, S., Stergiopoulos, T., Hiskia, A., Papaconstantinou, E., Bernard, M.C., Falaras, P. (2002). Preparation, characterization and photocatalytic activity of nanocrystalline thin film TiO2 catalysts towards 3,5-dichlorophenol degradation. J. Photochem. Photobiol. A: Chem. 149(1-3), 237-345.

Al-Rasheed, R., Cardin, D.J. (2003). Photocatalytic degradation of humic acid in saline waters. Part 1. Artificial seawater: influence of TiO2, temperature, pH, and air-flow. Chemosphere 51(9), 925-933.

Aiken,G. R., McKnight, D. M., Wershaw, R. L. and MacCarthy, P. (1985). Humic substances in soik, sediment, and water: Geochemistry, isolation, and Characterization. John Wiley & Sons, New York.

Bae, T.H., Tak, T.M. (2005). Effect of TiO2 nanoparticles on fouling mitigation of ultrafiltration membranes for activated sludge filtration. J. Membr. Sci. 249(1-2), 1-8.

Babaluo, A.A., Kokabi, M., Manteghian, M., Sarraf-Mamoory, R. (2004). A moditied model for alumina membranes formed by gel-casting followed by dip-coating.

國際替代計量

以TiO2光觸媒進行薄膜表面改質之研究

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