奈米薄膜應用於二價金屬(Ni、Cu、Co)離子之分離機制研究

Separate Mechanism of Divalent metal Cation (Ni、Cu、Co ) in Nanofiltration

張德民(De-Ming Chang)

指導教授 ： 陳孝行

國立臺北科技大學/工程學院/環境規劃與管理研究所/碩士(2007年)

摘要

本研究根據薄膜本身的特性以及二價陽離子之性質，欲探討薄膜截留二價陽離子(Ni、Cu、Co)之機制。研究中主要使用Hydranautics所生產的ESNA1-LF2奈米薄膜，討論奈米薄膜在單一(single)、混合(mixed)二價陽離子的條件下其截留率之差異比較，以及添加Cl-和SO42-對於截留效率之影響，而另外藉由比較GE-Osmonics之DK與ESNA1-LF2之薄膜孔徑以及表面電位等差異，探討二價陽離子與薄膜特性對於截留效率之關係。
本研究採用平板式模組進行實驗，薄膜表面電位則使用EKA(streaming potential measurements)測定，薄膜孔徑估算使用無極性有機物進行MWCO實驗，再利用經驗式求的薄膜孔徑。DK薄膜測定孔徑為1.47 nm大於ESNA之1.08 nm，但在低pH値下二價陽離受到DK表面正電荷之反斥現象截留率與孔徑較小之ESNA相似，顯示二價陽子與帶有正電荷之薄膜有反斥現象。
研究中二價陽離子以CuCl2、NiCl2、CoCl2分別進行單一及混合離子實驗，在單獨離子試驗中鎳、銅、鈷離子，截留效率分別為Ni＞Cu＞Co則是受到水合能效應之影響。而在混合離子試驗中水合能效應衰弱以表面電位以及空間障礙影響取而代之，以水合離子觀念中金屬離子與水分子中氧原子的鍵結長度為比較基準，Ni-O的距離為2.14 Å大於Cu-O鍵結長度2.103 Å，以空間障礙角度來看，銅離子由於鍵結長度比鎳離子短，因此較容易通過薄膜而使得截留效率略低於鎳子。而鎳、銅、鈷離子受到本身特性的影響下，在流通量以及擴散係數的差異響下濃度極化現象會有程度上的差異，其中濃度極化程度分別為Cu(2.81)＞Co(2.59)＞Ni(2.11)，顯示濃度極化程度愈大者與截留效率成反比。

關鍵字

薄膜表面電位 ； 薄膜孔徑 ； 濃度極化 ； 水合離子

並列摘要

This research, according to the characteristic of the membrane and divalent cations, is to investigate the separate mechanism of divalent cation(Cu, 63.5 Da; Ni, 58.7 Da and Co, 58.9 Da) through nanofiltration membranes, This studying uses two difference nanofiltration membrane, Using the ESNA-LF2 membrane to investigate the single and mixed solutions from the conducted experiments, and adding Cl-、SO42- to study the difference of the retention, At the same time, compared to ESNA-LF2、DK membrane two important features of steric hindrance and charge repulsive force.
This filtration experiment was performed with flat-sheet membrane. The experimental investigates the influence of the retention efficient by the membrane surface charge in different pH、membrane pore radius and compound ions in different concentration. The divalent cations retention were carried out for CuCl2、NiCl2 and CoCl2.And the effective membrane surface charge of the membrane was determined using zeta streaming potential measurement (EKA) techniques. Also, the ESNA-LF2 membrane is negatively, and DK has positively when pH in 3-5.On the other hand，The membrane pore radii were using filtration experiments with uncharged solutes(PEG、Glouse), DK membrane determines 1.47 nm that the radii is greater than ESNA for 1.08 nm, Because of the retention of divalent cations mechanism major by the influence of Donnan exclusion in this research. In low concentration cations has positively repulsive force by DK membrane.
Interestingly, although the order of molecular weight is Cu> Co >Ni , but in single solution, the rejection are Ni> Co> Cu in due to Hydration energy effect, In mixed solution, the Hydration energy effect decrease the rejection are Ni>Co>Cu because of the [M(H20)6]2+ structure, the distance of Ni-O (2.14 Å) is greater than Cu-O (2.103 Å). And the Ni、Co、Cu are influenced by solvent flux(J) and diffusion coefficient(Di) difference, the rejection will have difference due to the concentration polarization of the degree.

並列關鍵字

Nanofiltration ； Membrane surface charge ； Membrane pore radii ； Hydration energy ； concentration polarization

參考文獻

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36. 林宏儒，奈米薄膜阻塞現象之研究，碩士學位，國立成功大學環境工程研究所，2005，台南。

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