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

Membranes ◽  
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.

Effect of coagulation mechanisms on the fouling and ultrasonic cleaning of PTFE membrane

2012 ◽  
Vol 66 (11) ◽  
pp. 2291-2298 ◽  
Author(s):  
Meng-Wei Wan ◽  
Cybelle Morales Futalan ◽  
Cheng-Hung Chang ◽  
Chi-Chuah Kan
Keyword(s):  
Membrane Fouling ◽  
Permeate Flux ◽  
Cleaning Efficiency ◽  
Ultrasonic Cleaning ◽  
Ptfe Membrane ◽  
Pore Blocking ◽  
Dead End ◽  
Flux Decline ◽  
Cake Formation ◽  
Scanning Electron

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).

Electroflocculation as potential pretreatment in colloid ultrafiltration

2006 ◽  
Vol 6 (1) ◽  
pp. 69-78 ◽  
Author(s):  
T. Harif ◽  
M. Hai ◽  
A. Adin
Keyword(s):  
Membrane Fouling ◽  
Colloidal Suspension ◽  
Membrane Surface ◽  
Constant Current ◽  
Permeate Flux ◽  
Batch Mode ◽  
Membrane Behavior ◽  
Flux Decline ◽  
Stainless Steel Cathode ◽  
Marginal Improvement

Electroflocculation (EF) is a coagulation/flocculation process in which active coagulant species are generated in situ by electrolytic oxidation of an appropriate anode material. The effect of colloidal suspension pretreatment by EF on membrane fouling was measured by flux decline at constant pressure. An EF cell was operated in batch mode and comprised two flat sheet electrodes, an aluminium anode and stainless steel cathode, which were immersed in the treated suspension, and connected to an external DC power supply. The cell was run at constant current between 0.06–0.2A. The results show that pre-EF enhances the permeate flux at pH 5 and 6.5, but only marginal improvement is observed at pH 8. At all pH values cake formation on the membrane surface was observed. The differences in membrane behavior can be explained by conventional coagulation theory and transitions between aluminium mononuclear species which affect particle characteristics and consequently cake properties. At pH 6.5, where sweep floc mechanism dominates due to increased precipitation of aluminium hydroxide, increased flux rates were observed. It is evident that EF can serve as an efficient pretreatment to ultrafiltration of colloid particles.

Nanofiltration performance of lead solutions: effects of solution pH and ionic strength

2010 ◽  
Vol 10 (2) ◽  
pp. 193-200 ◽  
Author(s):  
Wuthikorn Saikaew ◽  
Supatpong Mattaraj ◽  
Ratana Jiraratananon
Keyword(s):  
Ionic Strength ◽  
Membrane Surface ◽  
Aromatic Polyamide ◽  
Solution Chemistry ◽  
Lead Ion ◽  
Solution Ph ◽  
Dead End ◽  
Flux Decline ◽  
Charged Membrane ◽  
Double Layer Thickness

Nanofiltration performance (i.e. rejection and flux decline) of lead solutions was investigated using a dead-end test cell at room temperature. An aromatic polyamide NF-90 membrane was chosen to determine the impacts of solution chemistry. The experimental results revealed that solution flux decline was dependent on solution pH, ionic strength, and type of lead solutions. Solution flux conducted with different types of lead solutions (i.e. PbCl2 and Pb(NO3)2) decreased with increased solution pH. Solutions having high pH exhibited greater flux decline than those having low solution pH, while lead ion rejections were relatively high. Increased ionic strengths resulted in a greater flux decline, while lead ion rejections decreased with decreasing solution pH and increasing ionic strengths. Such results were related to low solution pH, suggesting an increase in fixed charge of proton (H+), decreasing electrical double layer thickness within membrane, thus allowing increased lead concentration passing through the membrane surface. Solution flux and rejection decreased further at higher ionic strengths, which caused a reduced negatively charged membrane, and thus decreased rejections. It was also found that lead ion for PbCl2 solution exhibited higher rejections than that of Pb(NO3)2 solution.

Investigation of membrane fouling by synthetic and natural particles

2004 ◽  
Vol 50 (12) ◽  
pp. 279-285 ◽  
Author(s):  
J.H. Kweon ◽  
D.F. Lawler
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Research Articles ◽  
Clay Material ◽  
Dramatic Effect ◽  
Flux Decline ◽  
Scanning Electron

The biggest impediment for applying membrane processes is fouling that comes from mass flux (such as particle and organic matter) to the membrane surface and its pores. Numerous research articles have indicated that either particles or natural organic matter (NOM) has been the most detrimental foulant. Therefore, the role of particles in membrane fouling was investigated with two synthetic waters (having either particles alone or particles with simple organic matter) and a natural water. Membrane fouling was evaluated with flux decline behavior and direct images from scanning electron microscopy. The results showed that the combined fouling by kaolin and dextran (a simple organic compound selected as a surrogate for NOM) showed no difference from the fouling with only the organic matter. The similarity might stem from the fact that dextran (i.e., polysaccharide) has no ability to be adsorbed on the clay material, so that the polysaccharide behaves the same with respect to the membrane with or without clay material being present. In contrast to kaolin, the natural particles showed a dramatic effect on membrane fouling.

scholarly journals Effect of on the Membrane Distillation of PVDF Membrane Material Enhanced by Gas-Liquid Two-Phase Flow

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Membrane Surface ◽  
Threshold Level ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
High Concentration ◽  
Two Phase ◽  
Flux Enhancement ◽  
Membrane Performance ◽  
Flux Decline ◽  
Sweeping Gas

This study investigates the membrane performance and fouling control in the bubble-assisted sweeping gas membrane distillation with high concentration saline (333 K saturated solution) as feed. The results show that longer bubbling interval (3 min) at a fixed bubbling duration of 30s can most efficiently increase the the flux enhancement ratio up to 1.518. Next, the flux increases with the gas flowrate under a relatively lower level, but tends to a plateau after the threshold level (1.2 L•min-1). Compared to non-bubbling case, the permeate flux reaches up to 1.623 fold at a higher bubble relative humidity of 80 %. It was also found that greater flux enhancement can be achieved and meanwhile dramatic flux decline can be delayed for an intermittent bubbling system with a smaller nozzle size. These results accord well with the observations of fouling deposition in situ on the membrane surface with SEM.

scholarly journals Studies of polypropylene membrane fouling during microfiltration of broth with Citrobacter freundii bacteria

2015 ◽  
Vol 17 (4) ◽  
pp. 56-64 ◽  
Author(s):  
Marek Gryta ◽  
Marta Waszak ◽  
Maria Tomaszewska
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Transmembrane Pressure ◽  
Citrobacter Freundii ◽  
Permeate Flux ◽  
Process Duration ◽  
Polypropylene Membrane ◽  
Flux Decline ◽  
Cake Layer ◽  
Scanning Electron

Abstract In this work a fouling study of polypropylene membranes used for microfiltration of glycerol solutions fermented by Citrobacter freundii bacteria was presented. The permeate free of C. freundii bacteria and having a turbidity in the range of 0.72–1.46 NTU was obtained. However, the initial permeate flux (100–110 L/m2h at 30 kPa of transmembrane pressure) was decreased 3–5 fold during 2–3 h of process duration. The performed scanning electron microscope observations confirmed that the filtered bacteria and suspensions present in the broth formed a cake layer on the membrane surface. A method of periodical module rinsing was used for restriction of the fouling influence on a flux decline. Rinsing with water removed most of the bacteria from the membrane surface, but did not permit to restore the initial permeate flux. It was confirmed that the irreversible fouling was dominated during broth filtration. The formed deposit was removed using a 1 wt% solution of sodium hydroxide as a rinsing solution.

Formation and prevention of hardly removable particle layers in inside-out capillary membranes operating in dead-end mode

2003 ◽  
Vol 3 (5-6) ◽  
pp. 117-124 ◽  
Author(s):  
S. Panglisch
Keyword(s):  
Boundary Conditions ◽  
Membrane Surface ◽  
Cross Flow ◽  
Membrane Resistance ◽  
Permeate Flux ◽  
Dead End ◽  
Capillary Membrane ◽  
Theoretical Predictions ◽  
Capillary Membranes ◽  
Geometrical Boundary

Although numerous ultra- and microfiltration dead-end plants with capillary membranes are already operative, some phenomena are still unexplained. Therefore, the fundamental processes taking place inside a capillary membrane were observed. Initially, the flow field depending on axial and radial position inside the capillary was determined. Then, particle transport and deposition were theoretically studied by determination of particle trajectories considering influences of particle concentration and walleffects on hydrodynamics, DLVO-forces, buoyancy, gravitation, diffusion and interparticular forces. Following these calculations, incoming particles with a diameter smaller than the so-called “limiting diameter”, which depends on operational and geometrical boundary conditions, due to depositions are widely and evenly distributed. Larger particles do not deposit until they are at a certain distance from the water inlet. The larger the particle size, the longer the distance. If the particle is larger than the so-called “corkforming diameter” then the particles are transported to the dead-end of the capillary which may cause a clogging of the capillary. This “corkforming diameter” depends on operational as well on geometrical boundary conditions. These theoretical predictions are confirmed by experimental results from investigations with spherical latex and non-spherical walnut particles. To avoid this clogging, the deposition of the particles should be evenly distributed, which means that the “corkforming diameter” should be as large as possible. That goal could be achieved by operating the membrane plant with short and/or wide capillaries. However, a small permeate flux, a small membrane resistance and/or a small membrane surface potential succeed as well. Another possibility could be to operate the capillaries with a very small cross flow.

scholarly journals Verification of a Combined Fouling Model to Predict Flux Decline during Ultrafiltration of Organic Solutes

2018 ◽  
Vol 22 (2) ◽  
Author(s):  
I. N. H. M. Amin ◽  
A. W. Mohammad
Keyword(s):  
Early Stage ◽  
Membrane Surface ◽  
Organic Solutes ◽  
Filtration Time ◽  
Pvdf Membrane ◽  
Flux Decline ◽  
Cake Formation ◽  
Pore Blockage ◽  
Pes Membrane ◽  
Two Stages

Studies were conducted to investigate the blocking mechanism and flux decline behavior while treating organic solutes contained in glycerin-water solutions (triglycerides, TG and fatty acid, FA). Two ultrafiltration membranes were tested, polyethersulphone (PES 25 kDa) and polyvinylidenfluoride (PVDF 30 kDa) membranes. Influence of TG and its combination (TG-FA mixtures) as foulant models, pH of feed solutions (3–10) and membrane surface chemistry were investigated. Combined blocking model was applied and the fitting were discriminate that the flux decline of PES membrane was dominated by pore blockage at the early stage and later by cake resistance during the entire filtration time. However, for PVDF membrane, cake formation mechanism was acknowledged as the major contributor to the fouling mechanism for all the parameters tested. On the other hand, the model predicts there are two stages of filtration appeared to occur, involving pore blockage at the early stage followed by cake formation.

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