Mechanisms Study of Organic DBP Precursors Removal by Nanofiltration Membranes
Date Issued
2007
Date
2007
Author(s)
Lin, Yi-Li
DOI
en-US
Abstract
In this study, two types of commercial nanofiltration (NF) membranes (NF70 and NF270) were chosen to remove four model disinfection by-product (DBP) precursors (resorcinol, phloroglucinol, 3-hydroxybenzoic acid, and tannic acid) with different functional groups. The clean NF membranes were characterized by physico-chemical properties including molecular weight cutoff, membrane pore radius, hydrophobicity (contact angle measurement), membrane surface morphology (SEM and AFM), membrane surface charge (streaming potential measurement), membrane elemental composition (XPS and energy dispersive X-ray spectrometer, EDX) and surface roughness (AFM) to validate the NF rejection mechanisms of DBP precursors.
The filtration experiments of the model compounds were assessed under various pH values (3-10) in which the removal efficiencies for both membranes were reasonably good at high pH values. Electrostatic repulsion is the prevailing mechanism for the model compounds with negatively ionizable functional groups rejected by the negatively charged NF membranes at high pH values, while steric hindrance exclusion and adsorption are controlling factors for the rejection of unionized small organic molecules. The presence of calcium does not significantly affect model compounds retentions. The calcium rejection rises with the presence of model compounds as well as an increase of pH due to its formation of complex ion between calcium and model compounds.
For the examination of membrane surface roughness, it is essential to use the same scan area when comparing the surface roughness of different membranes. In general, membranes with rougher surface posses a higher fouling potential, which makes the flux decline more rapidly.
Subjects
奈米過濾
消毒副產物
鈣
流線電位
掃瞄式電子顯微鏡
原子力顯微鏡
X光光電子光譜
Nanofiltration
disinfection by-product
calcium
streaming potential
scanning electron microscopy (SEM)
atomic force microscopy (AFM)
x-ray photoelectron spectroscopy (XPS)
Type
thesis
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