Charge reversal of colloidal particlesS. Pianegonda, M. C. Barbosa and Y. Levin
Instituto de Física, Universidade Federal do Rio Grande do Sul CP 15051, 91501-970 Porto Alegre RS, Brazil
received 9 May 2005; accepted in final form 2 July 2005
published online 5 August 2005
A theory is presented for the effective charge of colloidal particles in suspensions containing multivalent counterions. It is shown that if colloids are sufficiently strongly charged, the number of condensed multivalent counterion can exceed the bare colloidal charge leading to charge reversal. Charge renormalization in suspensions with multivalent counterions depends on a subtle interplay between the solvation energies of the multivalent counterions in the bulk and near the colloidal surface. We find that the effective charge is not a monotonically decreasing function of the multivalent salt concentration. Furthermore, contrary to the previous theories, it is found that except at very low concentrations, monovalent salt hinders the charge reversal. This conclusion is in agreement with the recent experiments and simulations.
82.45.-h - Electrochemistry and electrophoresis.
82.70.Dd - Colloids.
© EDP Sciences 2005