Use of capacitive microsensors for concentration polarization characterization in pressure-driven crossflow membrane filtration

2005 ◽  
Author(s):  
Zhongxia Zhang ◽  
V.M. Bright ◽  
A.R. Greenberg
Keyword(s):  
Membrane Filtration ◽  
Concentration Polarization ◽  
Pressure Driven

Effect of the membrane potential on the performance of ultrafiltration membranes

1986 ◽  
Vol 51 (3) ◽  
pp. 539-544 ◽  
Author(s):  
Hans-Hartmut Schwarz ◽  
Vlastimil Kůdela ◽  
Jaromír Lukáš ◽  
Jiří Vacík ◽  
Volker Gröbe
Keyword(s):  
Membrane Potential ◽  
Concentration Polarization ◽  
Ultrafiltration Membranes ◽  
Membrane Cleaning ◽  
Gel Layer ◽  
Charged Membrane ◽  
Protein Molecules ◽  
Polysulfone Membranes ◽  
Pressure Driven

In the pressure driven process the performance of membranes for ultrafiltration can be changed by incorporating charged groups into the membranes. sulfonation of polysulfone membranes the membrane potential is varied. On interaction of the negatively charged membrane with positively or negatively charged protein molecules the formation of a concentration polarization gel layer proceeds at different rate. Thus, the performance of the membrane can be controlled by the membrane potential. The dependence of the performance on the potential is discussed and procedures for membrane cleaning are suggested.

The Effect of Flow Pulsation on Ultrafiltration System Limiting Flux Behavior

2013 ◽  
Author(s):  
Chyouhwu Brian Huang ◽  
Hung-Shyong Chen
Keyword(s):  
Membrane Filtration ◽  
Concentration Polarization ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Paper Industry ◽  
Surface Concentration ◽  
Permeate Flux ◽  
Filtration Time ◽  
Protection Systems ◽  
Oil Water

Ultrafiltration (UF) is an important industrial operation and is found in the food industry, separation of oil-water emulsions, treatment effluents from the pulp and paper industry, and environmental protection systems. Despite being widely used in these areas, UF systems exhibit a limiting flux behavior caused by concentration polarization on the membrane surface. Concentration polarization can be severe in macromolecular solutions due to low diffusivity on membrane separation and both mechanical and chemical methods have been used to reduce this phenomenon. This study introduces a new mechanical method that improves the performance of membrane separation and decreases concentration polarization. It involves pulsing the feed flow discontinuously and based on our results, feed flow velocity and solution bypass/membrane filtration time ratio are two vital factors when it comes to improving permeate flux. The proposed method is expected to find wide application, particularly in the processing of macromolecular solution.

Methods to Reduce Concentration Polarization and Fouling in Membrane Filtration

1994 ◽  
Vol 59 (4) ◽  
pp. 737-755 ◽  
Author(s):  
Petr Mikulášek
Keyword(s):  
Membrane Filtration ◽  
Morphological Analysis ◽  
Concentration Polarization ◽  
Membrane Separation ◽  
Separation Processes ◽  
Membrane Modules

Various methods and concepts that are currently being used and proposed to control or minimize concentration polarization and fouling in membrane separation processes are reviewed. A morphological analysis of hydrodynamic ways to prevent the detrimental influence on fluxes is given. The potentials of these different approaches are analyzed and some examples of module designs resulting from the various approaches with special attention to rotary membrane modules are given.

Simulation of Forward Osmosis Flow in a Two-Dimensional Asymmetric Membrane Channel With Draw Channel Circular Baffle Implementation

2015 ◽  
Author(s):  
James R. L. Koch ◽  
Ramesh K. Agarwal
Keyword(s):  
Osmotic Pressure ◽  
Pressure Loss ◽  
Membrane Filtration ◽  
Concentration Polarization ◽  
Fluid Dynamic ◽  
Forward Osmosis ◽  
Cross Flow ◽  
Cfd Modeling ◽  
Asymmetric Membrane ◽  
Asymmetric Membranes

Forward Osmosis (FO) driven asymmetric membrane filtration is a developing technology which shows promise for seawater desalination and wastewater treatment. Due to the fact that asymmetric membranes are widely used in conjunction with this technology, internal concentration polarization (ICP), a flow-entrainment effect occurring within such membranes, is a significant if not dominant source of overall osmotic pressure loss across the membrane. Accurate modeling of ICP effects is therefore very critical for accurate Computational Fluid Dynamic (CFD) modeling of asymmetric membranes. A related, dilutive effect known as external concentration polarization (ECP) also develops on both the rejection and draw sides of the membrane, further contributing to osmotic pressure loss. In order to increase the overall water flux, circular spacers can be implemented within the draw channel of FO cross-flow membrane exchange units to decrease the effects of ICP and draw ECP. The drawback of spacer inclusions is an increased pressure loss across the length of the feed channel. The system efficiency gained by the decrease in ECP must therefore be weighed against the energy cost of hydraulically making up lost channel pressure. To model the geometry of a FO cross-flow channel, the open source CFD package OpenFOAM is used. A compressible flow model with explicit boundary conditions is developed to simulate the flux transfer and ICP effects present within an asymmetric membrane when exposed to a NaCl solution. Results are validated by comparison with the numerical data generated by earlier models of asymmetric membranes implemented by other investigators using similar simulation conditions.

The Fluid Mechanics of Membrane Filtration

2007 ◽  
Author(s):  
Jack S. Hale ◽  
Alison Harris ◽  
Qilin Li ◽  
Brent C. Houchens
Keyword(s):  
Membrane Filtration ◽  
Concentration Polarization ◽  
Membrane Surface ◽  
Convective Transport ◽  
Contaminated Water ◽  
Permeate Flux ◽  
Large Pressure ◽  
Cake Layer ◽  
Large Pressure Gradient ◽  
Concentration Polarization Layer

Reverse osmosis and nanofiltration membranes remove colloids, macromolecules, salts, bacteria and even some viruses from water. In crossflow filtration, contaminated water is driven parallel to the membrane, and clean permeate passes through. A large pressure gradient exists across the membrane, with permeate flow rates two to three orders of magnitude smaller than that of the crossflow. Membrane filtration is hindered by two mechanisms, concentration polarization and caking. During filtration, the concentration of rejected particles increases near the membrane surface, forming a concentration polarization layer. Both diffusive and convective transport drive particles back into the bulk flow. However, the increase of the apparent viscosity in the concentration polarization layer hinders diffusion of particles back into the bulk and results in a small reduction in permeate flux. Depending on the number and type of particles present in the contaminated water, the concentration polarization will either reach a quasi-steady state or particles will begin to deposit onto the membrane. In the later case, a cake layer eventually forms on the membrane, significantly reducing the permeate flux. Contradictive theories suggest that the cake layer is either a porous solid or a very viscous (yield stress) fluid. New and refined models that shed light on these theories are presented.

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