Modelling of dead-end microfiltration with pore blocking and cake formation

In this study, the effect of coagulation pretreatment on membrane fouling and ultrasonic cleaning efficiency was investigated using a dead-end polytetrafluoroethylene (PTFE) microfiltration system. The extent of membrane fouling was examined under different coagulation mechanisms such as charge neutralization (CN), electrostatic patch effect (EPE) and sweep flocculation (SW). Fouling through EPE mechanism provided the greatest flux decline and least permeate flux recovery over CN and SW. EPE produces more stable, smaller and more compact flocs while CN and SW have large, easily degraded and highly-branched structured flocs. The predominant fouling mechanism of EPE, CN and SW is pore blocking, a combination of pore blocking and cake formation, and cake formation, respectively. Better permeate flux recovery is observed with SW over CN and EPE, which implies formation of less dense and more porous cake deposits. The morphology of fouled membranes was examined using scanning electron microscopy (SEM).

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Membrane pore blocking during cake formation in constant pressure and constant flux dead-end microfiltration of very dilute colloids

Chemical Engineering Science ◽

10.1016/j.ces.2014.09.052 ◽

2015 ◽

Vol 122 ◽

pp. 465-473 ◽

Cited By ~ 18

Author(s):

Eiji Iritani ◽

Nobuyuki Katagiri ◽

Toshiharu Takenaka ◽

Yuuki Yamashita

Keyword(s):

Constant Pressure ◽

Membrane Pore ◽

Constant Flux ◽

Pore Blocking ◽

Dead End ◽

Cake Formation

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Interdependence of Contributing Factors Governing Dead-End Fouling of Nanofiltration Membranes

Membranes ◽

10.3390/membranes11010047 ◽

2021 ◽

Vol 11 (1) ◽

pp. 47

Author(s):

Oranso Themba Mahlangu ◽

Bhekie Brilliance Mamba

Keyword(s):

Membrane Surface ◽

Contact Angles ◽

Permeate Flux ◽

Contributing Factors ◽

Pore Blocking ◽

Dead End ◽

Flux Decline ◽

Cake Formation ◽

Affinity Interaction

Cake-enhanced concentration polarization (CECP) has been ascribed as the main cause of flux decline in dead-end filtration. An unfamiliar approach was used to investigate the role of CECP effects in the fouling of a nanofiltration membrane (NF-270) that poorly reject salts. Membrane–foulant affinity interaction energies were calculated from measured contact angles of foulants and membrane coupons based on the van der Waals/acid–base approach, and linked to resistance due to adsorption (Ra). In addition, other fouling mechanisms and resistance parameters were investigated using model organic and colloidal foulants. After selection, the foulants and membranes were characterized for various properties, and fouling experiments were conducted under controlled conditions. The fouled membranes were further characterized to gain more understanding of the fouling layer properties and flux decline mechanisms. Sodium alginate and latex greatly reduced membrane permeate flux as the flux declined by 86% and 59%, respectively, while there was minor flux decline when aluminum oxide was used as model foulant (<15% flux decline). More flux decline was noted when fouling was conducted with a combination of organic and colloidal foulants. Contrary to other studies, the addition of calcium did not seem to influence individual and combined fouling trends. Foulants adsorbed more on the membrane surface as the membrane–foulant affinity interactions became more attractive and pore blocking by the foulants was not important for these experiments. Hydraulic resistance due to cake formation (Rc) had a higher contributing effect on flux decline, while CECP effects were not substantial.

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