Removal of humic substances(HSs) by electro-membrane filtration
Date Issued
2005
Date
2005
Author(s)
Weng, Yu-Hsiang
DOI
zh-TW
Abstract
薄膜程序為一不需相轉換的固液分離程序，然而往往因薄膜積垢問題使得操作成本增加，限制了薄膜程序的應用。腐植質被認為是造成薄膜淨水積垢的主因之一，然而微過濾程序並無法有效去除腐植質。本研究以實驗室規模的外加電場薄膜過濾模組，處理模擬水樣中之帶負電的腐植質。本研究之薄膜過濾實驗結果顯示，施加100 V電壓時，可將腐植質去除率由低於20%提升至80%以上，經由SUVA、THMPF及液態氫核磁共振的分析結果顯示，被去除的有機物主要為帶電較多、分子量子量較大且含有脂肪族-3及芳香族的部分，這些官能基易與氯反應而產生三鹵甲烷，故外加電場薄膜程序應用在去除消毒副產物之前驅物質上，深具應用潛力。再者，外加電場薄膜程序去除腐植質的機制主要是物理的分離作用，即電泳的作用，化學氧化還原雖然也有發生，但不是主要的因子。由於腐質植是相當複雜的有機物，腐植質去除率不僅與施加的電場強度有關，亦於薄膜孔徑有關。另外，外加電場亦可增加過濾通量及減少過濾阻力，增加的原因除了上述電泳之外，當外加電場大於臨界電場時，其電滲透現象則具有增加過濾通量之功能。當以脈衝式電場操作薄膜過濾，雖可減少所需電力，並且可增加過濾通量，但腐植質去除率較連續電場施加時為低，故在工程實務不建議使用。
Membrane process is a solid-liquid operation which involves no phase transition, and therefore energy cost could be minimized. In water treatment microfiltration (MF) and ultrafiltration (UF), humic substances (HSs) is believed to be one of the important foulants which would cause flux decline and increase process cost. However, MF and UF could not remove HSs effectively due to their large pore size in comparison with HSs. In this study, a bench-scale electro-membrane filtration system was developed to treat synthetic HSs solution. The results showed that the removal of the negatively charged HSs increased from 20% to more than 80% in terms of UV254, DOC and trihalomethane formation potential (THMFP) via 100 V. Specific ultraviolent absorbance (SUVA), THMFP, and solution 1H nuclear magnetic resonance (1H NMR) results suggest that those HSs with large molecular weight and charge are removed after applying voltage through membrane. Furthermore, those aromatic and aliphatic 3 fractions have high potential to react with chlorine to produce trihalomethane. The results also demonstrate that electrophoresis dominates the removal mechanism despite the minor chemical reactions did change HSs in somewhat. The removal efficiency of HSs is not only dependent on the applied electric field strength, but also dependent on the pore size of the membrane due to inhomogeneity of HSs. In addition, the filtration flux was increased and resistance was decreased after applying electric field through membrane. When the applied electric field strength was greater than critical electric field strength, electro-osmotic flux plays important role on flux enhancement. Although applying pulsed electric field to membrane also reduces flux decline and moreover reduce the power consumption, HSs rejection was deteriorated in comparison with applying constant electric field.
Subjects
腐植質
外加電場薄膜過濾
SUVA
THMPF
液態氫核磁共振
humic substances (HSs)
electro-membrane filtration
solution 1H nuclear magnetic resonance (1H NMR)
Type
thesis
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