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.

The new concept of flux enhancement during cell separation with MF/UF processes

2001 ◽  
Vol 1 (5-6) ◽  
pp. 381-386
Author(s):  
A. Kołtuniewicz
Keyword(s):  
Cell Separation ◽  
High Efficiency ◽  
Membrane Surface ◽  
Cross Flow ◽  
Dry Mass ◽  
High Energy ◽  
Process Conditions ◽  
Permeate Flux ◽  
Flux Enhancement ◽  
Flow Systems

The microfiltration and ultrafiltration processes are considered as matured membrane processes that are well established in industrial practice. Nevertheless, the main obstacles of their further development in the new competitive implementations are the economical problems. The key economic factors are permeate flux and energy consumption. However, although the cross-flow systems enable us to attain higher flux, it is usually very expensive. The high energy is consumed to maintain circulation velocity of the retentate that is sufficient for sweeping out the retained component from the membrane surface. Moreover in the case of cells separation the high intensity of the fouling and low cake permeability makes it necessary to apply additional efforts, such as backflushing, backpulsing, promoters of turbulence, vibrations, ultrasounds and many other. Therefore, dead-end systems are still quite competitive with cross-flow, especially for diluted (less than 0.5% of dry mass) suspensions or solutions. Cell separation with membranes is one of the most vivid problems for modern biotechnology, wastewater and water treatment. Membranes offer mild process conditions and high selectivity of separation. This enables us to solve a variety of problems such as cell culturing, fractionation, concentration, purification and sterilisation. The selected cells may be precisely separated from other components of broth and subsequently directed into the reaction space again in good conditions to ensure a quasi-continuous mode of operation. Moreover, membranes enable us to attain high efficiency of the bioconversion by removal of all product and inhibitors directly from the bioreactor. This is the reason for the huge interest in cell separation with membranes. The idea of the paper was to present the new concept of flux enhancement for cell separation on membranes. This concept lies in taking advantage of the specific rheological nature of biopolymers, which are the main foulants. The biopolymers retained on the membrane surface (i.e. on the top layer) can be applied as a lubricant for the cells that can settle on such a ‘movable layer’. As is shown, further in the paper, the thickness of the moving layer is lower and the flux is greater. The common movement of the cells and gel layer is very convenient from the cells integrity point of view. However the hydrodynamic conditions always play an important role in cross-flow systems; the resistance of ultrafiltration membranes may be reduced much more when compared with more open microfiltration membranes.

Ultrafiltration of Aqueous Solutions of Food Dye in the Presence of Surfactants

2017 ◽  
Vol 68 (1) ◽  
pp. 6-10
Author(s):  
George Alexandru Popa ◽  
Daniela Florentina Popa (Enache) ◽  
Dumitra Daniela Slave (Clej) ◽  
Ion Din Spiridon ◽  
Cristina Monica Mirea ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Membrane Surface ◽  
Cross Flow ◽  
Sodium Octanoate ◽  
Food Dye ◽  
Cross Flow Filtration ◽  
Dead End ◽  
Food Dyes ◽  
Flow Filtration ◽  
Quinoline Yellow

The objective of the study is the low-pressure membrane process for treating aqueous solutions containing food dyes and surfactants. The influence of surfactants (SDS � sodium dedecil sulphate, SO � sodium octanoate) in the separation of synthetic food dyes (E104 � quinoline yellow) was analyzed. Polysulfone and polysulfone-polyaniline membranes were used. Dye and surfactant concentrations used were 10% (equivalent to 100g/m3). The pressures used in the ultrafiltration process were 0.1, 0.2 and 0.3 MPa. When dye containing solutions were passed through the membranes, an increase in their flux was observed. The presence of surfactants in the solutions lead to a decline in flux when pressures of 0.1 and 0.2 MPa were used, but an improvement could be seen as the pressure increased to 0.3 MPa, for both dead-end and cross-flow filtration. Using only dead-end alternative, higher fluxes were achieved for both membranes, but it decreases with time due to accumulation on the membrane surface. The use of cross-flow filtration did not allow accumulation on the membrane surface so that the flux was constant in time.The use of anionic surfactants improved the food dye retention. The interactions between membranes and surfactants can be an important factor supporting the efficiency of the ultrafiltration.

Effect of flow-rate on ethanol separation in membrane distillation process

2013 ◽  
Vol 67 (9) ◽  
Author(s):  
Marek Gryta
Keyword(s):  
Flow Rate ◽  
Membrane Surface ◽  
Positive Influence ◽  
Membrane Distillation ◽  
Alcohol Concentration ◽  
Process Conditions ◽  
Capillary Membrane ◽  
Enrichment Coefficient ◽  
Capillary Membranes ◽  
Separation Degree

AbstractThe separation of diluted ethanol solutions and fermentation broths by membrane distillation was investigated. The influence of stream flow-rate on the ethanol flux was studied. An evaluation of the process conditions on the separation degree of ethanol was performed with the application of hydrophobic capillary membranes composed of polypropylene. By removing the alcohol via membrane distillation, it is possible to achieve a higher content of ethanol in the permeate than that in the broth. The enrichment coefficient amounted to 4–6.5, and decreased with an increase of the ethanol concentration in the broth. It was found that the flow-rate affects the value of the enrichment coefficient. A positive influence of carbon dioxide on the ethanol transport through the capillary membrane was observed. The evolution of CO2 bubbles from the broth increases the stream turbulence, probably enhancing the alcohol concentration in the layer adjacent to the membrane surface.

Numerical Simulation of Filtration of Charged Oil Particles in Stationary and Rotating Tubular Membranes

2015 ◽  
Author(s):  
Sina Jahangiri Mamouri ◽  
Volodymyr V. Tarabara ◽  
André Bénard
Keyword(s):  
Flow Field ◽  
Electric Field ◽  
Electric Potential ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Cross Flow ◽  
Solid Cylinder ◽  
Permeate Flux ◽  
Cross Flow Filtration ◽  
Flow Filtration

Cross flow filtration (CFF) is a common membrane separation process with applications in food, biochemical and petroleum industries. In particular, membranes can be used for liquid-liquid separation processes such as needed in oil-water separation. A major challenge in cross flow filtration is membrane fouling. It can decrease significantly the permeate flux and a membrane’s efficiency. Membrane fouling can be mitigated by inducing shear on the membrane’s surface and this can be enhanced by inducing a swirl in the flow. In addition, a possible approach to improve membrane efficiency consists of repelling droplets/particles from the porous surface toward the centerline using a repulsive electric force. For this purpose, the surface of the membrane can be exposed to electric potential and droplets/particles are also induced to have the same electric charge. In this work, numerical simulations of charged non-deformable droplets moving within an axially rotating charged tubular membrane are performed. The results show that by increasing the electric potential on the membrane surface, the repelling force increases which obviously improves the grade efficiency of the membrane. However, the electric field gradients found in the flow field require large potentials on the membrane surface to observe a noticeable effect. Hence, a smaller solid cylinder is located in the centerline of the flow channel with zero potential. This solid cylinder enhances the electric field gradient in the domain which results in higher repelling forces and larger grade efficiency of the membrane at small potentials. The addition of a small cylinder in the flow field also improves the grade efficiency increases due to the higher shear stress near the membrane surface.

scholarly journals Membrane surface properties and their effects on real waste oil-in-water emulsion ultrafiltration

Water SA ◽  
2019 ◽  
Vol 45 (3 July) ◽  
Author(s):  
Marjana Simonič
Keyword(s):  
Surface Properties ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Cross Flow ◽  
Influential Factors ◽  
Permeate Flux ◽  
Chemical Cleaning ◽  
Water Emulsion ◽  
Oil In Water ◽  
Oil In Water Emulsion

Membrane surface properties and their effect on the efficiency of ultrafiltration (UF) of real waste oily emulsions was studied. Experiments were performed in cross-flow operation at total recycle condition in a lab-scale system. The ceramic UF membrane in the tubular type module was employed. During the experiments permeate flux was measured. The most important influential factors, such as temperature, TMP, and pH, were considered during the experiments. Zeta potential was measured in order to explain the phenomena on the membrane surface. The isoelectric point of the fouled membrane was shifted to the alkaline range. COD removal efficiency reached 89%. Gas chromatography measurements were performed in order to determine the composition of waste emulsions. SEM micrographs showed the formation of calcite on the membrane, which contributed to membrane fouling. Chemical cleaning was examined using alkaline and acid solutions, and a cleaning strategy was determined.

Ceramic Cross-Flow Microfiltration in the Presence of Inserts

1997 ◽  
Vol 62 (12) ◽  
pp. 1879-1887 ◽  
Author(s):  
Petr Mikulášek ◽  
Jiří Cakl ◽  
Zbyněk Petráš
Keyword(s):  
Membrane Surface ◽  
Cross Flow ◽  
Extensive Study ◽  
Metal Working ◽  
Permeate Flux ◽  
Tube System ◽  
Oil Emulsion ◽  
Steady State Flux ◽  
Empty Tube ◽  
And Migration

The influence of inserts with various configurations on permeate flux through a tubular ceramic microfiltration membrane was studied. The commercial metal-working oil emulsion was used in the experiments. A more extensive study of the effect of shear rate on permeate flux was made by comparing the steady-state flux of the empty tube system and the system with inserts. The cross-flow microfiltration with inserts was found to be simple and effective. Analysing experimental results, it was concluded that the introduction of inserts, irrespective of their configurations, resulted in a significant increase in permeate flux compared with results obtained in the empty tube system. The interruption of formation of a boundary layer by the inserts is attributed to mixing and migration of rejected particles from the membrane surface.

scholarly journals DETERMINATION OF FOULING MECHANISM IN ULTRAFILTRATION OF ELECTROPLATING WASTEWATER

2018 ◽  
Vol 80 (3-2) ◽  
Author(s):  
Danu Ariono ◽  
Anita Kusuma Wardani ◽  
Putu Teta Prihartini Aryanti ◽  
Ahmad Nurul Hakim ◽  
I Gede Wenten
Keyword(s):  
Flow Velocity ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Cross Flow ◽  
Permeate Flux ◽  
High Concentration ◽  
Filtration Time ◽  
Electroplating Wastewater ◽  
Fouling Mechanism ◽  
Cross Flow Velocity

Wastewater from electroplating industries is usually contaminated with high concentration of hazardous materials, such as nickel, copper, and chromium. Therefore, the electroplating wastewater is one of the environmental problems that require a novel solution to reduce risks for human and environment. Ultrafiltration is a promising technology to overcome this problem due to its ability to reject all suspended solids. However, membrane fouling still becomes a major obstacle in ultrafiltration processes. Fouling reduces the permeate flux and increases membrane operational costs due to membrane cleaning. In this work, fouling mechanism that occurred in polyacrylonitrile based ultrafiltration for electroplating wastewater treatment was investigated. The effects of trans-membrane pressure (TMP) and cross flow velocity on fouling mechanism were also studied. The results showed that in the first 20 minutes, intermediate blocking was occurred on the membrane surface, while cake formation was happened for the rest of filtration time. These results were applied for all TMP and cross flow velocity.

Removal of Humic Substances by UF and NF Membrane Systems

1999 ◽  
Vol 40 (9) ◽  
pp. 121-129 ◽  
Author(s):  
Rulin Bian ◽  
Yoshimasa Watanabe ◽  
Norihito Tambo ◽  
Genzo Ozawa
Keyword(s):  
Humic Substances ◽  
Removal Efficiency ◽  
Membrane Surface ◽  
Cross Flow ◽  
Molecular Size ◽  
Bulk Water ◽  
Flow Mode ◽  
Permeate Flux ◽  
Strong Shear ◽  
Uf Membranes

This paper deals with the removal efficiency and mechanisms of humic substances contained in a river water by ultrafiltration (UF) and nanofiltration (NF) membranes. UF membranes with molecular weight cut-off (MWCO) of 50 kDa to 200 kDa can remove only large molecular size humic substances (LMSHS). Even in the UF membranes operated under the cross-flow mode, the LMSHS were accumulated on the membrane surface, because the back transport velocity of LMSHS is always smaller than that of the permeate flux. Precoagulation enhanced the removal of humic substances effectively. The optimum coagulation conditions for removing the humic substances in the UF membranes was the same as that in the conventional coagulation/flocculation/sedimentation process. The vibration action increased the removal efficiency of humic substances in the NF membrane process. Strong shear produced by the vibration diffused away the humic substances from the membrane surface to the bulk water, therefore the accumulation of humic substances on/near the membrane surface, i.e. formation of cake and concentration polarization boundary layers, is prohibited.

Comparison of ceramic capillary membrane and ceramic tubular membrane with inserted static mixer

2011 ◽  
Vol 65 (5) ◽  
Author(s):  
Igor Gaspar ◽  
Andras Koris ◽  
Zsolt Bertalan ◽  
Gyula Vatai
Keyword(s):  
Specific Energy Consumption ◽  
Cross Flow ◽  
Ceramic Membranes ◽  
High Price ◽  
Transmembrane Pressure ◽  
Permeate Flux ◽  
Water Emulsion ◽  
Oil In Water ◽  
Capillary Membranes ◽  
Tubular Membranes

AbstractOily wastewaters are produced in large amounts in many fields of food, mechanical, and other types of industry. In order to protect the environment, wastewaters must not be discharged directly into sewers. First, they must be cleaned at least down to 50 mg L−1 of oil content (according to Hungarian standard). In previous research, the authors found that oil-in-water emulsions can be separated with filtration using ceramic ultrafiltration tubular membranes. The relatively high price of ceramic membranes can be compensated by the fact that this separation process can be significantly intensified by static mixers inside the tubular membranes. New generations of ceramic membranes are the ceramic capillary membranes. These two different types of membranes and their effects on permeate flux, oil retention and specific energy consumption were compared in this work. The results, obtained with a stable oil-in-water emulsion as feed, showed that the use of novel ceramic capillary membranes at optimal operating cross-flow rate and transmembrane pressure is reasonable. The results have also shown the advantage of static mixing in the lumen side of the membrane tube providing a wider range of satisfactory separation level and increased permeate flux.

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