Effects of cations on the formation of ultrafiltration membrane fouling layers when filtering fulvic acid

Fulvic acid (FA) is the main water-soluble component in humic substances which usually cause membrane fouling in the drinking water treatment process. This study investigates the ultrafiltration membrane fouling characteristics and mechanisms caused by FAs in the presence of various salt ions (Ca2+,...

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Bibliographic Details
Published in:Desalination 2014-11, Vol.352, p.174-180
Main Authors: Tang, Congcong, He, Zhangwei, Zhao, Fangbo, Liang, Xiaoyang, Li, Zhanshuang
Format: Article
Language:English
Subjects:
Aggregates
Applied sciences
Cake layer
Cations
Chemical engineering
Divalent cations
Drinking water and swimming-pool water. Desalination
Exact sciences and technology
Flux
Fouling
Fulvic acid
Gel layer
Membrane separation (reverse osmosis, dialysis...)
Membranes
Monovalent cations
Pollution
Scanning electron microscopy
Ultrafiltration
Ultrafiltration membrane fouling
Water treatment and pollution
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Summary:Fulvic acid (FA) is the main water-soluble component in humic substances which usually cause membrane fouling in the drinking water treatment process. This study investigates the ultrafiltration membrane fouling characteristics and mechanisms caused by FAs in the presence of various salt ions (Ca2+, Mg2+, K+ and Na+). A series of experiments had been carried out to characterize the decline of permeate flux, pollutant rejection, FA aggregates, and the morphology of the membrane's fouling layer. Compared with pure FA solution, FA-monovalent solution containing cations (K+ and Na+) caused much lower permeate flux and smaller amount of fouling layer, which was difficult to remove by flushing with water. The presence of divalent cations (Ca2+ and Mg2+), caused the permeate flux to noticeably increase and membrane fouling can be easily removed. Laser particle size analysis showed that the FA formed larger aggregates in the presence of Ca2+ or Mg2+ cations. Based on an atomic force microscope and scanning electron microscope analysis, results showed that monovalent cations made the colloids form a gel layer, which led to pore blocking and permeate flux decrease. And divalent cations reacted with FA and formed a cake layer of larger particles creating porous structures on the membrane surface. •Membrane fouling caused by FAs with existence of cations has been investigated.•Monovalent cations (K+ & Na+) caused membrane pore blocking by forming a gel layer.•Divalent cations reacted with FAs and formed a cake layer with porous structures.•Different valence states of ions could influence the NOM in different ways.
ISSN:0011-9164
1873-4464
DOI:10.1016/j.desal.2014.08.020