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Streaming Potential And Streaming Current of a Particle Covered Surface

Streaming Potential And Streaming Current of a Particle Covered Surface. Part 1 Krzysztof Sadlej ZMiFP IPPT PAN. Overview. Introduction Electrical Double Layer ( EDL ) Gouy-Chapman-Stern model Electrokinetics Electro-osmosis Electrophoresis

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Streaming Potential And Streaming Current of a Particle Covered Surface

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  1. StreamingPotential And StreamingCurrent of a ParticleCoveredSurface Part 1 Krzysztof Sadlej ZMiFPIPPT PAN

  2. Overview • Introduction • Electrical Double Layer (EDL) • Gouy-Chapman-Stern model • Electrokinetics • Electro-osmosis • Electrophoresis • Streamingcurrent/Streamingpotential • MeasuringtheStreamingPotential • Particlesadsorbedattheinterface – whatchanges?

  3. Inspirers, Co-Workers • Prof.. ZbigniewAdamczyk (IKiFP PAN) • WligiuszWajnryb (IPPT PAN) • Maria Ekiel-Jeżewska (IPPT PAN) • JerzyBławzdziewicz (Yale University)

  4. Introduction • Charge…

  5. Electrical Double Layer (EDL) Stern layer Diffuse layer Zeta-potential

  6. Gouy-Chapman-Sternmodel Bulk concentration of ions Concentration of ions Poisson-Boltzmann equation:

  7. Gouy-Chapman-Stern model • Solution method od the Poisson-Boltzmann eq. • Debye-Hückel approx. Works only for • Gouy-Chapman model: • Flat surface • Symmetric electrolite zi = z+ = z- = z Debye-Hückel parameter

  8. Gouy-Chapman-Stern model

  9. Gouy-Chapman-Stern model • Diffuselayer charge • Adsorbed charge intheinner region (Stern layer, Stern 1924, Graham 1947) • No charge withinthelayer of thicknessδi

  10. Gouy-Chapman-Sternmodel • What is the charge distribution in the layer δ? • Uniform space charge distribution, distant-dependent permittivity Or • All ions are assumed to be confined to a layer and are treated as point charges.

  11. Electro-Osmosis • Motion of liquid induced by an applied electric field Stokes equations Slip velocity Smoluchowski 1903

  12. Electrophoresis • Motion of suspended particles in an applied electric field Electrophoretic mobility Smoluchowski 1921

  13. Streamingcurrent and StreamingPotential • Current appearing due to double-layer charge movementwiththe fluid • Transfer of charge downstream (due to pressure gradient) isbalanced by currentdue to electric field • Potential drop associated withthis field: STREAMINGPOTENTIAL

  14. Streamingcurrent and StreamingPotential • Current appearing due to double-layer charge movementwiththe fluid • Transfer of charge downstream (due to pressure gradient) isbalanced by currentdue to electric field • Potential drop associated withthis field: STREAMINGPOTENTIAL

  15. Streamingcurrent and StreamingPotential • Current appearing due to double-layer charge movementwiththe fluid • Transfer of charge downstream (due to pressure gradient) isbalanced by currentdue to electric field • Potential drop associated withthis field: STREAMINGPOTENTIAL

  16. Streaming current and Streaming Potential Pressuredifference Poiseuille flow in a tube: Tubelength Electric current due to convection: Dominant contribution from the double layer:

  17. Streaming current and Streaming Potential Balance of currents: Streamingpotential Electroliteconductivity

  18. MeasuringtheStreamingPotential M. Zembala et al. Colloids and Surfaces A 195 (2001), 3-15

  19. Particlesadsorbedattheinterface – whatchanges? Rapiddecrease of thestreamingcurrent/potentialwithparticleconcentrationθ

  20. To be continued… • Canthisdependence be explainedtheoretically?? • Hydrodynamics • StatisticalPhysics • Virialexpansion, Simulations

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