Removal of small trihalomethane precursors
from aqueous solution by nanofiltration
張怡怡
Lin YL;Chiang PC;Chang EE
摘要Abstract
The removal of small trihalomethane precursors (THMPs) from aqueous solution by two commercial nanofiltration membranes (NF70 and
NF270) was investigated. Resorcinol, phloroglucinol, and 3-hydroxybenzoic acid were selected as model compounds of small THMPs, while
tannic acid was chosen as a medium molecular disinfection by-product (DBP) precursor for comparison. The performance of nanofiltration
membranes were evaluated by introducing polyethylene glycol (PEG) solutions and uncharged saccharides to estimate molecular weight cut-off
(MWCO) and membrane pore radii, respectively. The streaming potential was measured to estimate the membrane surface charge at different pH
values, which reveals that the NF270 membrane is more pH-sensitive than the NF70 membrane. The rejections of the above selected THMPs were
assessed under various pH values, and the removal efficiencies of THMPs for both membranes at high pH values are reasonably well. Charge
exclusion is the prevailing mechanism for the selected small model compounds retended by the negatively charged nanofiltration membranes,
while size exclusion and adsorption are controlled mechanisms but not sufficient for the rejection of unionized small organic molecules. In general,
the NF270 membrane exhibits the superior permeation rate value, which takes an advantage over the NF70 membrane from the aspect of energy
