Real-scale chlorination at pH4 of BW30 TFC membranes and their physicochemical characterization

Chlorination remains a big hurdle in membrane technology as the most commonly used membranes for water purification consist of a polyamide top-layer, which is not fully resistant towards chlorine-induced oxidation. In this work, DOW FILMTEC™ BW30 membrane elements were systematically chlorinated wit...

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Bibliographic Details
Published in:Journal of membrane science 2018-04, Vol.551, p.123-135
Main Authors: Verbeke, Rhea, Gómez, Verónica, Koschine, Tönjes, Eyley, Samuel, Szymczyk, Anthony, Dickmann, Marcel, Stimpel-Lindner, Tanja, Egger, Werner, Thielemans, Wim, Vankelecom, Ivo F.J.
Format: Article
Language:English
Subjects:
Active chlorination
Analytical chemistry
Chemical Sciences
PALS
Pilot-scale
Polyamide
Tightening effect
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Summary:Chlorination remains a big hurdle in membrane technology as the most commonly used membranes for water purification consist of a polyamide top-layer, which is not fully resistant towards chlorine-induced oxidation. In this work, DOW FILMTEC™ BW30 membrane elements were systematically chlorinated with NaOCl at pilot-scale under acidic conditions (pH4) at 10bar for 2.5h. Variations in membrane performance and their physicochemical properties were determined by ATR-FTIR, XPS, WD-XRF, SEM, AFM and zeta-potential measurements. With increasing bleaching concentration, both membrane roughness and chlorine incorporation via N- and ring-chlorination increased, while surface charge remained quasi unaltered. Both water flux and salt passage decreased proportionally over the whole concentration range. Accordingly, positron annihilation lifetime spectroscopy (PALS) revealed a decrease in the size of the top-layer free-volume elements as chlorine concentration increased, confirming, for the first time in a quantitative manner, the so-called tightening effect. The obtained results also show that thin-film composite (TFC) membranes are altered differently when chlorinated under pressure than via simple immersion, as conventionally performed in literature. •DOW FILMTEC™ BW30 8″ modules were chlorinated (0, 1, 2, 50ppm) at pH4 under industrial conditions.•With increasing chlorine concentration, the salt passage and water flux dropped proportionally.•The so-called tightening effect of PA could be quantitatively proven for the first time via PALS.•The application of pressure during the chlorination process is an important parameter in the ageing process.
ISSN:0376-7388
1873-3123
DOI:10.1016/j.memsci.2018.01.019