高分子奈米薄膜過濾電解質溶液之探討

A Study on the Nanofiltration of Electrolytic Solutions Using Polymeric Membrane

陳沂仁(Yi-Ren Chen)

指導教授 ： 鄭東文

淡江大學/工學院/化學工程與材料工程學系碩士班/碩士(2005年)

https://doi.org/10.6846/TKU.2005.00579

摘要

本研究以濾餅過濾與掃流過濾，在不同之電解質溶液下，改變其濃度、壓力以及攪拌速度等條件進行實驗，對於濾速、阻隔率、有效質傳係數、穿透率以及薄膜表面電荷進行討論。
濾餅過濾選用MWCO為100和500之Spectrum薄膜，而掃流過濾則是選用MWCO為150~300之Desal DK薄膜進行實驗，實驗結果顯示不論是濾餅過濾系統與掃流過濾系統下，濾液量皆會隨著透膜壓差的增加而增加；在固定壓力下，隨著溶質濃度的上升，濾速有降低的趨勢。因為帶電奈米薄膜對於二價陰離子SO4－的排斥力大於一價陰離子Cl－和NO3－，所以二價離子有較高之阻隔率。奈米薄膜阻擋電解質的主要的因素為電荷效應，其影響是大於篩選效應的影響。
本文另以Nernst–Planck方程式為基準，針對於不同的電解質下，利用濾速與阻隔率估算有效質傳係數與穿透濾，再藉由穿透率與濃度變化的關係，估算出各電解質對於薄膜表面形成之電荷密度。

關鍵字

奈米過濾 ； 電解質 ； 濾餅過濾 ； 掃流過濾 ； 電荷密度

並列摘要

In this study, The changes of permeate flux, solute rejection, effective salt transfer coefficient, solute transmittance and membrane charge density were measured in dead-end or cross-flow filtration module under various operating parameters such as electrolytic solutions concentration, pressure, and stirring velocity.
Two nanofiltration membranes of 100 and 500 Da were tested in dead-end filtration, while 150~300 Da nanofiltration membrane was used in cross-flow filtration. The results show that the increase in pressure leads to the increase in flux. At constant pressure, the flux decreases with increasing solute concentration. The retention of divalent sulphate ion by the membrane is higher than that of the monovalent ion (Cl- or NO3-), thus, the charge effect is more important than the sieving effect when the electrolytic solutions were filtrated in the nanofiltration membranes.
A method combing the extended Nernst-Planck equation with the data of flux and rejection was developed to calculate the effective mass transfer coefficient and solute transmittance. From those transport parameters, the surface charge density of membrane can be determined under various electrolytic solution.

並列關鍵字

Nanofiltration ； Electrolytic Solutions ； Dead-end ； Cross-Flow ； Charge density

參考文獻

Bowen, W. R., H. Mukhtar, “Charaterisation and prediction of separation performance of nanofiltration membranes.” Journal of Membrane Science, 112 (1996) 263.

Bowen, W. R., A. W. Mohammad, N. Hilal, “Characterisation of nanofiltration membranes for predictive purposes-use of salts, uncharged solutes and atomic force microscopy, ” Journal of Membrane Science, 126 (1997) 91.

Bowen, W. R., A. W. Mohammad, “Diafiltration by Nanofiltration: Prediction and Optimization,” American Institute of Chemical Engineers Journal, 44 (1998) 1799.

Bowen, W. R., T. A. Doneva, “Atomic force microscopy of manofiltration membranes: surface morphology, pore size distribution and adhesion.” Desalination, 129 (2000) 163.

Bowen, W. R., J. S. Welfoot, “Modelling the performance of membrane nanofiltration – critical assessment and model development.” Chemical Engineering Science, 57 (2002) 1121.