濾餅厚度與流線電位關係之探討

在薄膜過濾程序中，膜結垢的發生會導致濾速嚴重衰減及選擇穿透性下降，在密閉過濾系統中，以往僅能由濾速之衰減判定膜結垢阻力，但膜結垢變化是連續的，如何於過濾程序中即時監控膜結垢程度是極重要之課題。目前欲藉由電動量測監控膜結垢已有數位學者提出，本研究以電動現象之量測，分別以0.1μm MCE及0.1μm PC兩種不同材質及特性之薄膜來對0.5wt% MX-1000進行dead-end濾餅過濾實驗，探討濾液通量及濾餅厚度做一分析，並理論分析恆壓與恆濾速操作下之濾餅厚度與流線電位變化值之關係，且比較電極之構造與位置對流線電位值量測之影響。實驗結果顯示，當恆壓濾餅過濾之操作條件為粒子帶電性較低之pH值時，因膜材與進料溶液中之粒子靜電排斥力低，粒子較易附著於膜材表面上形成濾餅，使其濾液通量下降，當提高進料懸浮液於pH為7後，膜材與粒子之帶電量皆上升，彼此之靜電排斥力所造成之影響增大，粒子於膜面之附著量減少，因此通量衰減速度較低pH為3時慢。過濾初期，流線電位變化值隨濾餅厚度上升而增加，當濾餅厚度堆積至一定程度後，濾餅層厚度上升較緩慢，因此理論與實驗上之流線電位變化於過濾後期趨向平緩，但於定量上略有差異。比較兩不同電極組所測得之流線電位變化發現，距離膜面12mm之電極構造比距離膜面35mm之電極符合模擬，原因為較長電極之末端接有一環且較接近膜表面，當膜面濾餅厚度不均時，較長之電極距離濾餅層較接近，其較易測得有效流線電位值。恆濾速濾餅過濾操作下，獲得之濾餅厚度與時間約呈線性增加關係。濾餅厚度對流線電位值之實驗數據與模擬於定性及定量分析上皆為遞增趨勢，雖仍有差異存在，但過濾後期之差距比過濾初期小，是因過濾初期濾速變化較大，導致粒子開始附著於膜面上時流線電位不穩定，但過濾後期濾餅量增多，且濾速穩定，使過濾後期之數據，於定性及定量上差距較小。

關鍵字

濾餅過濾；流線電位；恆濾速過濾；恆壓過濾

並列摘要

In membrane filtration processes, membrane fouling usually leads the decline of filtration rate quite substantially and sometime also results in an unacceptable rejection of targeted component in selective separation. In an enclosed filtration system, it is very difficult to directly observe the fouling layer growth. Due to the growth of fouling layer is time dependent, how to on-line detection of membrane fouling is very important for membrane processes. Several studies have applied the electrokinetic method to characterize membrane fouling. In this study, experiments of constant pressure and constant rate with dead-end cake filtration were carried out to measure the time dependent streaming potential. Theoretical analyses for the relationships between cake thickness and streaming potential were simulated and compared with the experimental values. Two membranes, 0.1μm MCE and PC, which have much small pore size than the particles MX-1000 for preparing the suspensions were used to prevent the internal fouling in the membrane pore. Experimental results from constant pressure filtration showed that , when the particles have low zeta potential, the filtrate flux will decline more obvious because the low electrostatic repulsions between membrane and particles and between particles each other has a positive effect on particle deposition and formation of denser cake layer. At the initial stage of filtration, streaming potential increases with cake thickness and then . when the cake is growing to a certain thickness at the filtration later period, the change of streaming potential tend to be very slight. Both experimental and theoretical values in streaming potential vs. cake thickness show a well agreement in qualitatively, but there is still some quantitative differences. Compare the streaming potential measured by two different electrodes with that by simulation shows that the electrode which is connected with a ring and closer to the membrane surface can measure streaming potential value effectively. Under constant rate filtration, streaming potential increases with the cake thickness. The simulation result of streaming potential at initial stage filtration has a larger difference as compared with the experimental data, while both show a well agreement at the later period of filtration. The larger difference is caused by the variation of filtration rate which is not easy to be adjusted as a constant at the initial stage of filtration.

並列關鍵字

Constant rate filtration ； constant pressure filtration ； dead-end filtration ； streaming potential

參考文獻

江宜蓁 (2003). 薄膜電荷量測與膜過濾電動現象分析. 碩士學位論文, 私立中原大學化學工程研究所, 中壢市.

陳志文 (2009). 以流線電位法分析薄膜過濾程序之結垢. 中原大學化學工程研究所學位論文, 1-132. 中壢市.

蔡宗諺 (2007). 薄膜結垢與流線電位關係之探討. 中原大學化學工程研究所學位論文, 1-100. 中壢市.

Benavente, J., and Jonsson, G. (1998). Effect of adsorbed protein on the hydraulic permeability, membrane and streaming potential values measured across a microporous membrane. Colloids and Surfaces A: Physicochemical and Engineering Aspects 138, 255-264.

Bowen, W. R., and Cao, X. (1998). Electrokinetic effects in membrane pores and the determination of zeta-potential. Journal of Membrane Science 140, 267-273.

國際替代計量

濾餅厚度與流線電位關係之探討

全文下載

主題瀏覽