Comparison of zeta potentials and structure for statistical mechanical theories of a model cylindrical double layer Article uri icon


  • The zeta potential and the structure of a model cylindrical double layer obtained through the Poisson-Boltzmann theory, the hypernetted chain/mean spherical approximation integral equation theory, the modified Poisson-Boltzmann theory, and the density functional theory are compared with the corresponding Monte Carlo simulation results. The cylindrical double layer consists of an infinitely long cylinder with a uniform surface charge immersed in a restricted primitive model electrolyte (equi-sized, rigid spherical ions in a continuum dielectric). Calculations have been performed at room temperature and in a water-like solvent for 1:1, 2:2, 2:1/1:2 valency electrolytes for different electrolyte concentrations, axial charge parameters (surface charge densities), and ionic diameters. The results for the zeta potential, the mean electrostatic potential, and the electrode-ion singlet distributions predicted by the formal statistical mechanical theories reproduce the simulation data to a high level of accuracy overall for the range of physical parameters studied. The theoretical predictions, except that due to the classical mean field theory, also reveal a remarkable consistency among themselves. The results also (a) explore the relationship between the occurrence of charge reversal and the negative derivative of the mean electrostatic potential,(b) provide insight into the connection between reversed and extremal values of the zeta potential versus surfaced charge density curves and some aspects of electrokinetics, viz., inverted electrophoretic velocities and the possible existence of differently charged colloids with the same mobility, and (c) suggest a plausible identification of the integrated surface charge density at a point near the cylindrical polyion surface with the electrokinetic charge. © 2017 Elsevier B.V.

publication date

  • 2018-01-01