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Lianfa Song - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of Concentration Polarization in a reverse osmosis channel with parabolic crossflow.
    Water environment research : a research publication of the Water Environment Federation, 2014
    Co-Authors: Cui Liu, Audra Morse, Ken Rainwater, Lianfa Song
    Abstract:

    Concentration Polarization in narrow reverse osmosis channels with parabolic crossflow was numerically simulated with finite different equations related to permeate velocity, crossflow velocity, average salt Concentration, and wall salt Concentration. A significant new theoretical development was the determination of two correction functions, F2 and F3, in the governing equation for average salt Concentration. Simulations of Concentration Polarization under various conditions were then presented to describe the features of the new model as well as discussions about the differences of Concentration Polarizations of the more realistic parabolic flow with those when plug flow or shear flow was assumed. The situations in which the simpler models based on shear or plug flow can be used were indicated. Concentration Polarization was also simulated for various conditions to show the applicability of the model and general features of Concentration Polarization in a narrow, long reverse osmosis channel.

  • Concentration Polarization in a narrow reverse osmosis membrane channel
    Aiche Journal, 2009
    Co-Authors: Lianfa Song
    Abstract:

    Concentration Polarization in a narrow reverse osmosis channel is bounded by the channel height and under the influence of variable transverse velocity. An attempt was made in this article to quantify Concentration Polarization in such a narrow membrane channel. The transverse velocity in the membrane channel was first determined and its impact on Concentration Polarization was investigated. Based on the concept of retained salt, analytical equations were developed for the wall salt Concentration at an arbitrary point in the narrow membrane channel. Finally, development of Concentration Polarization in typical reverse osmosis channels under various conditions was numerically simulated and discussed. Interesting results on the details of Concentration Polarization in the narrow reverse osmosis channel that had never been reported before were revealed with this mechanistic model.

  • A numerical study on Concentration Polarization and system performance of spiral wound RO membrane modules
    Journal of Membrane Science, 2005
    Co-Authors: Wenwen Zhou, Lianfa Song, Tay Kwee Guan
    Abstract:

    The development of Concentration Polarization in a spiral wound reverse osmosis membrane channel and the dePolarization effect of spacers are important concerns for understanding the performance of membrane processes. However, an accurate quantification of these effects derived from fundamental principles is impractical due to the complexity of the processes. In this study, a macroscopic method was developed to estimate the effect of Concentration Polarization on the performance of the spiral wound membrane modules. Concentration Polarization in a channel filled with spacers was described as a combination of two extreme cases, namely the undisturbed Concentration Polarization and complete dePolarization (uniform distribution across the channel height). With the introduction of a Polarization factor for the degree of Concentration Polarization, a mathematical model was developed for the permeate flux in the spiral wound modules. The proposed model was solved numerically to simulate the performance of a long membrane channel under various operation conditions. The simulation results demonstrated that the model developed in this study was a feasible way to estimate Concentration Polarization in spiral wound modules. Excellent fitness was found between the numerical simulations and experimental observations of the average permeate fluxes in along membrane channel of spiral wound membrane modules.

  • Concentration Polarization in cross-flow reverse osmosis
    AIChE Journal, 1999
    Co-Authors: Lianfa Song
    Abstract:

    A dimensionless governing equation was formulated for a cross-flow RO process in which the local variation of Concentration Polarization was rigorously considered. It was shown in this formulation that the cross-flow RO process could be fully characterized with a single dimensionless parameter. The coupling between permeate flux and Concentration Polarization was properly solved and a closed-form analytical solution was obtained. This analytical solution enabled us to conveniently investigate Concentration Polarization in the RO process. The significance of local variation of Concentration Polarization was demonstrated, and the operations of RO under various conditions were simulated and investigated with the newly developed model.

  • theory of Concentration Polarization in crossflow filtration
    Journal of the Chemical Society Faraday Transactions, 1995
    Co-Authors: Lianfa Song, Menachem Elimelech
    Abstract:

    A novel theory is developed for Concentration Polarization of non-interacting particles in crossflow-filtration systems. This theory reveals that the extent of Concentration Polarization, as well as the behaviour of the permeate flux, are characterized by an important dimensionless filtration number (NF= 4πa3pΔP/3kT). There is a critical value of the filtration number for a given suspension and operational conditions. When the filtration number is smaller than the critical value, a Polarization layer exists directly over the membrane surface and the wall particle Concentration is determined by the pressure and temperature. At higher filtration numbers, a cake layer of retained particles forms between the Polarization layer and the membrane surface. Mathematical models are constructed for both cases and analytical solutions for the permeate flux are derived. An increase in permeate flux with increasing pressure is predicted for all operational conditions.

Sung Jae Kim - One of the best experts on this subject based on the ideXlab platform.

  • Capillarity ion Concentration Polarization as spontaneous desalting mechanism.
    Nature communications, 2016
    Co-Authors: Sungmin Park, Yeonsu Jung, Seok Young Son, Inhee Cho, Youngrok Cho, Hyomin Lee, Ho-young Kim, Sung Jae Kim
    Abstract:

    To overcome a world-wide water shortage problem, numerous desalination methods have been developed with state-of-the-art power efficiency. Here we propose a spontaneous desalting mechanism referred to as the capillarity ion Concentration Polarization. An ion-depletion zone is spontaneously formed near a nanoporous material by the permselective ion transportation driven by the capillarity of the material, in contrast to electrokinetic ion Concentration Polarization which achieves the same ion-depletion zone by an external d.c. bias. This capillarity ion Concentration Polarization device is shown to be capable of desalting an ambient electrolyte more than 90% without any external electrical power sources. Theoretical analysis for both static and transient conditions are conducted to characterize this phenomenon. These results indicate that the capillarity ion Concentration Polarization system can offer unique and economical approaches for a power-free water purification system.

  • Capillarity ion Concentration Polarization for spontaneous biomolecular preConcentration mechanism
    Biomicrofluidics, 2016
    Co-Authors: Hyomin Lee, Seok Young Son, Sung Jae Kim, Pilnam Kim
    Abstract:

    Ionic hydrogel-based ion Concentration Polarization devices have been demonstrated as platforms to study nanoscale ion transport and to develop engineering applications, such as protein preConcentration and ionic diodes/transistors. Using a microfluidic system composed of a perm-selective hydrogel, we demonstrated a micro/nanofluidic device for the preConcentration of biological samples using a new class of ion Concentration Polarization mechanism called "capillarity ion Concentration Polarization" (CICP). Instead of an external electrical voltage source, the capillary force of the perm-selective hydrogel spontaneously generated an ion depletion zone in a microfluidic channel by selectively absorbing counter-ions in a sample solution. We demonstrated a reasonable preConcentration factor (∼100-fold/min) using the CICP device. Although the efficiency was lower than that of conventional electrokinetic ICP operation due to the absence of a drift ion migration, this mechanism was free from the undesirable instability caused by a local amplified electric field inside the ion depletion zone so that the mechanism should be suitable especially for an application where the contents were electrically sensitive. Therefore, this simple system would provide a point-of-care diagnostic device for which the sample volume is limited and a simplified sample handling is demanded.

  • nanofluidic Concentration devices for biomolecules utilizing ion Concentration Polarization theory fabrication and applications
    Chemical Society Reviews, 2010
    Co-Authors: Sung Jae Kim, Yong Ak Song, Jongyoon Han
    Abstract:

    Recently, a new type of electrokinetic Concentration devices has been developed in a microfluidic chip format, which allows efficient trapping and Concentration of biomolecules by utilizing ion Concentration Polarization near nanofluidic structures. These devices have drawn much attention not only due to their potential application in biomolecule sensing, but also due to the rich scientific content related to ion Concentration Polarization, the underlying physical phenomenon for the operation of these electrokinetic Concentration devices. This tutorial review provides an introduction to the scientific and engineering advances achieved, in-depth discussion about several interesting applications of these unique Concentration devices, and their current limitations and challenges.

  • Concentration Polarization and nonlinear electrokinetic flow near a nanofluidic channel.
    Physical review letters, 2007
    Co-Authors: Sung Jae Kim, Ying-chih Wang, Jeong Hoon Lee, Hongchul Jang, Jongyoon Han
    Abstract:

    A perm-selective nanochannel could initiate Concentration Polarization near the nanochannel, significantly decreasing (increasing) the ion Concentration in the anodic (cathodic) end of the nanochannel. Such strong Concentration Polarization can be induced even at moderate buffer Concentrations because of local ion depletion (therefore thicker local Debye layer) near the nanochannel. In addition, fast fluid vortices were generated at the anodic side of the nanochannel due to the nonequilibrium electro-osmotic flow (EOF), which was at least approximately 10x faster than predicted from any equilibrium EOF. This result corroborates the relation among induced EOF, Concentration Polarization, and limiting-current behavior.

Menachem Elimelech - One of the best experts on this subject based on the ideXlab platform.

  • influence of concentrative and dilutive internal Concentration Polarization on flux behavior in forward osmosis
    Journal of Membrane Science, 2006
    Co-Authors: Jeffrey R Mccutcheon, Menachem Elimelech
    Abstract:

    Osmosis through asymmetric membranes has been studied as a means of desalination via forward osmosis and power generation through a process known as pressure retarded osmosis. The primary obstacle to using asymmetric membranes for osmotic processes is the presence of internal Concentration Polarization, which significantly reduces the available osmotic driving force. This study explores the impact of both concentrative and dilutive internal Concentration Polarization on permeate water flux through a commercially available forward osmosis membrane. The coupling of internal and external Concentration Polarization is also investigated. A flux model that accounts for the presence of both internal and external Concentration Polarization for the two possible membrane orientations involving the feed and draw solutions is presented. The model is verified by data obtained from laboratory-scale experiments under well controlled conditions in both membrane orientations. Furthermore, the model is used to predict flux performance after hypothetical improvements to the membrane or changes in system conditions.

  • cake enhanced Concentration Polarization a new fouling mechanism for salt rejecting membranes
    Environmental Science & Technology, 2003
    Co-Authors: Eric M V Hoek, Menachem Elimelech
    Abstract:

    Results from well-controlled colloidal fouling experiments with reverse osmosis (RO) and nanofiltration (NF) membranes suggest the existence of a new source of flux decline for salt-rejecting membranescake-enhanced osmotic pressure. The physical mechanisms leading to this enhanced osmotic pressure are a combination of hindered back-diffusion of salt ions and altered cross-flow hydrodynamics within colloidal deposit layers, which lead to an enhanced salt Concentration Polarization layer. A model that accounts for both hindered diffusion of salt ions and altered hydrodynamics within colloidal deposit (“cake”) layers is presented. The model successfully links permeate flux and salt rejection to cake-enhanced Concentration Polarization and provides new insight into the mechanisms through which salt-rejecting membranes foul. Experimental data support the model calculations and highlight the role of enhanced Concentration Polarization phenomena in the performance (i.e., water flux and salt rejection) of polymer...

  • Coupled model of Concentration Polarization and pore transport in crossflow nanofiltration
    Aiche Journal, 2001
    Co-Authors: Subir Bhattacharjee, Jim C. Chen, Menachem Elimelech
    Abstract:

    A coupled model of Concentration Polarization and pore transport of multicomponent salt mixtures in crossflow nanofiltration rigorously predicts local variations of ionic Concentrations, flux and individual ion rejections along a rectangular crossflow filtration channel by a coupled solution of the convective-diffusion and extended Nernst-Planck equations. Coupling the pore transport model with the multicomponent convective-diffusion equation in the Concentration Polarization layer provides a comprehensive understanding of the interplay between Concentration Polarization and salt rejection. The coupled model is used to predict the local variations of ion rejection, permeate flux and mixture composition in a rectangular crossflow filtration channel for three-component salt mixtures. The total membrane surface Concentration of the ions and the ratio of different ions in the mixture (salt ratio) can change considerably along a crossflow filtration channel, and, consequently, cause remarkable variations in intrinsic ion rejections with axial position in the channel.

  • Concentration Polarization of Interacting Solute Particles in Cross-Flow Membrane Filtration
    Journal of colloid and interface science, 1999
    Co-Authors: Subir Bhattacharjee, Albert S. Kim, Menachem Elimelech
    Abstract:

    A theoretical approach for predicting the influence of interparticle interactions on Concentration Polarization and the ensuing permeate flux decline during cross-flow membrane filtration of charged solute particles is presented. The Ornstein-Zernike integral equation is solved using appropriate closures corresponding to hard-spherical and long-range solute-solute interactions to predict the radial distribution function of the solute particles in a concentrated solution (dispersion). Two properties of the solution, namely the osmotic pressure and the diffusion coefficient, are determined on the basis of the radial distribution function at different solute Concentrations. Incorporation of the Concentration dependence of these two properties in the Concentration Polarization model comprising the convective-diffusion equation and the osmotic-pressure governed permeate flux equation leads to the coupled prediction of the solute Concentration profile and the local permeate flux. The approach leads to a direct quantitative incorporation of solute-solute interactions in the framework of a standard theory of Concentration Polarization. The developed model is used to study the effects of ionic strength and electrostatic potential on the variations of solute diffusivity and osmotic pressure. Finally, the combined influence of these two properties on the permeate flux decline behavior during cross-flow membrane filtration of charged solute particles is predicted.

  • theory of Concentration Polarization in crossflow filtration
    Journal of the Chemical Society Faraday Transactions, 1995
    Co-Authors: Lianfa Song, Menachem Elimelech
    Abstract:

    A novel theory is developed for Concentration Polarization of non-interacting particles in crossflow-filtration systems. This theory reveals that the extent of Concentration Polarization, as well as the behaviour of the permeate flux, are characterized by an important dimensionless filtration number (NF= 4πa3pΔP/3kT). There is a critical value of the filtration number for a given suspension and operational conditions. When the filtration number is smaller than the critical value, a Polarization layer exists directly over the membrane surface and the wall particle Concentration is determined by the pressure and temperature. At higher filtration numbers, a cake layer of retained particles forms between the Polarization layer and the membrane surface. Mathematical models are constructed for both cases and analytical solutions for the permeate flux are derived. An increase in permeate flux with increasing pressure is predicted for all operational conditions.

Gilad Yossifon - One of the best experts on this subject based on the ideXlab platform.

  • Effect of advection on transient ion Concentration-Polarization phenomenon.
    Physical review. E, 2017
    Co-Authors: Leon Rosentsvit, Sinwook Park, Gilad Yossifon
    Abstract:

    Here, we studied the effect of advection on the transient ion Concentration-Polarization phenomenon in microchannel-membrane systems. Specifically, the temporal evolution of the depletion layer in a system that supports net flow rates with varying Péclet values was examined. Experiments complemented with simplified analytical one-dimensional semi-infinite modeling and numerical simulations demonstrated either suppression or enhancement of the depletion layer propagation against or with the direction of the net flow, respectively. Of particular interest was the third-species fluorescent dye ion Concentration-Polarization dynamics which was further explained using two-dimensional numerical simulations that accounted for the device complex geometry.

  • Effect of advection on transient ion Concentration-Polarization phenomenon.
    Physical Review E, 2017
    Co-Authors: Leon Rosentsvit, Sinwook Park, Gilad Yossifon
    Abstract:

    Here, we studied the effect of advection on the transient ion Concentration-Polarization phenomenon in microchannel-membrane systems. Specifically, the temporal evolution of the depletion layer in a system that supports net flow rates with varying Peclet values was examined. Experiments complemented with simplified analytical one-dimensional semi-infinite modeling and numerical simulations demonstrated either suppression or enhancement of the depletion layer propagation against or with the direction of the net flow, respectively. Of particular interest was the third-species fluorescent dye ion Concentration-Polarization dynamics which was further explained using two-dimensional numerical simulations that accounted for the device complex geometry.

Hideto Matsuyama - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Modeling of Concentration Polarization in Spacer-filled Channel with Permeation across Reverse Osmosis Membrane
    Industrial & Engineering Chemistry Research, 2015
    Co-Authors: Toru Ishigami, Hideto Matsuyama
    Abstract:

    This paper presents a numerical simulation method for reasonably describing Concentration Polarization in a spacer-filled channel of a spiral-wound reverse osmosis membrane module. The permeation across the membrane was modeled theoretically, based on nonequilibrium thermodynamics. We then simulated flow and mass transfer in a periodic unit model of the spacer-filled channel, with different Reynolds numbers, spacer separations, and angles between spacers, using the proposed method as a boundary condition for the reverse osmosis membrane. The results show that the Concentration Polarization and water flux distribution on the membrane surface can be reasonably well expressed by the simulation. The present numerical method is effective for modeling Concentration Polarization, and provides better descriptions of the flow and mass transfer characteristics in the spacer-filled channel than previous simulation methods.