Sedimentation of binary mixtures of like- and oppositely charged colloids: the primitive model or effective pair potentials?

Abstract

We study sedimentation equilibrium of low-salt suspensions of binary mixtures of charged colloids, both by Monte Carlo simulations of an effective colloids-only system and by Poisson-Boltzmann theory of a colloid-ion mixture. We show that the theoretically predicted lifting and layering effect, which involves the entropy of the screening ions and a spontaneous macroscopic electric field [J. Zwanikken and R. van Roij, Europhys. Lett. {\bf 71}, 480 (2005)], can also be understood on the basis of an effective colloid-only system with pairwise screened-Coulomb interactions. We consider, by theory and by simulation, both repelling like-charged colloids and attracting oppositely charged colloids, and we find a re-entrant lifting and layering phenomenon when the charge ratio of the colloids varies from large positive through zero to large negative values.

References in corpus (3)

• Extended sedimentation profiles in charged colloids: the gravitational length, entropy, and electrostatics
• Colloidal brazil nut effect in sediments of binary charged suspensions
• The sediment of mixtures of charged colloids: segregation and inhomogeneous electric fields

Cited by in corpus (6)

• The polydisperse cell model: Non-linear screening and charge renormalization in colloidal mixtures
• Phase behavior of a deionized binary mixture of charged spheres in the presence of gravity
• A Case Study of Sedimentation of Charged Colloids: The Primitive Model and the Effective One-Component Approach
• Colloidal Brazil nut effect in microswimmer mixtures induced by motility contrast
• Structural correlations and phase separation in binary mixtures of charged and uncharged colloids
• Realisation of the Brazil-nut effect in charged colloids without external driving