{"title":"Ion steric interactions and electrostatic correlations on electro-osmotic flow in charged nanopores with multivalent electrolytes","authors":"Shubhra Sahu, Bapan Mondal, Somnath Bhattacharyya","doi":"10.1103/physrevfluids.9.074201","DOIUrl":null,"url":null,"abstract":"Atomistic and coarse-grained simulations show the formation of a condensed layer of counterions near a charged surface in contact with multivalent or monovalent electrolytes of high concentration. This condensed layer may overscreen the surface charge, and eventually a coion-dominated region may arise within the electric double layer, which again draws a layer of counterions and so on till the charge density approaches zero. Such a type of overscreening and charge density oscillation cannot be predicted through the mean-field based models as it does not account for the correlations between discrete charges. In the present study the mean-field-based model has been extended to consider the many-body interactions to analyze the electro-osmosis and ion transport of multivalent electrolytes in a highly charged nanopore. The ions are considered to be finite-sized, which is accounted for by considering the hydrodynamic steric interactions and modification of the suspension medium viscosity. Consideration of the electrostatic correlation leads to a fourth-order Poisson-Fermi equation for an electric field. Such a type of continuum model is easy to handle and to use to predict the layered structure of the EDL. Our model captures the existing experimental and molecular dynamics simulation correctly. Based on the modified model, we have analyzed the volume flow rate, current density, and ion selectivity of the pore in multivalent electrolytes for different electrostatic conditions. The present model shows that the counterion size has an impact on the condensed layer and hence overscreening. We demonstrate that the EOF reversal of multivalent electrolytes can be suppressed by mixing with monovalent slats.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.5000,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physical Review Fluids","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1103/physrevfluids.9.074201","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSICS, FLUIDS & PLASMAS","Score":null,"Total":0}
引用次数: 0
Abstract
Atomistic and coarse-grained simulations show the formation of a condensed layer of counterions near a charged surface in contact with multivalent or monovalent electrolytes of high concentration. This condensed layer may overscreen the surface charge, and eventually a coion-dominated region may arise within the electric double layer, which again draws a layer of counterions and so on till the charge density approaches zero. Such a type of overscreening and charge density oscillation cannot be predicted through the mean-field based models as it does not account for the correlations between discrete charges. In the present study the mean-field-based model has been extended to consider the many-body interactions to analyze the electro-osmosis and ion transport of multivalent electrolytes in a highly charged nanopore. The ions are considered to be finite-sized, which is accounted for by considering the hydrodynamic steric interactions and modification of the suspension medium viscosity. Consideration of the electrostatic correlation leads to a fourth-order Poisson-Fermi equation for an electric field. Such a type of continuum model is easy to handle and to use to predict the layered structure of the EDL. Our model captures the existing experimental and molecular dynamics simulation correctly. Based on the modified model, we have analyzed the volume flow rate, current density, and ion selectivity of the pore in multivalent electrolytes for different electrostatic conditions. The present model shows that the counterion size has an impact on the condensed layer and hence overscreening. We demonstrate that the EOF reversal of multivalent electrolytes can be suppressed by mixing with monovalent slats.
期刊介绍:
Physical Review Fluids is APS’s newest online-only journal dedicated to publishing innovative research that will significantly advance the fundamental understanding of fluid dynamics. Physical Review Fluids expands the scope of the APS journals to include additional areas of fluid dynamics research, complements the existing Physical Review collection, and maintains the same quality and reputation that authors and subscribers expect from APS. The journal is published with the endorsement of the APS Division of Fluid Dynamics.