The spherical double layer: A hypernetted chain mean spherical approximation calculation for a model spherical colloid particle

The structure of an electrolyte around a spherical, charged colloid particle is studied, using a simple model in which the diameter of the ions in the soution is considered. The hypernetted chain mean spherical approximation (HNC/MSA) equation is derived and solved numerically. As a result the ionic distribution around the colloid particle is obtained. Calculations are made for 1:1 and 2:2 electrolytes for various values of the concentration, colloid radius, and electrical charge. By use of these ionic distributions, excess charge adsorption isotherms and zeta potentials are calculated. These quantities are compared with the nonlinear Poisson-Boltzmann (PB) results. Important quantitative and qualitative differences between the PB and HNC/MSA are found The zeta potential is found to be a nonmonotonic function of various parameters, for example, the charge density. Qualilative agreement with experimental results for the zeta potential is found. © 1989 American Chemical Society.

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