INTERACTIONS BETWEEN A CHARGE-REGULATED PARTICLE AND A CHARGED SURFACE

The interaction between a charge-regulated particle and a rigid planar surface of constant surface charge density immersed in an a : b electrolyte solution is examined. The general case that the timescale for the relaxation of the ions in an electrical double layer and the dissociation of the functional groups on the particle surface are comparable, is considered. Three models are discussed: the present dynamic model; the equilibrium model which assumes that both the ions in the double layer and the dissociation reaction on the particle surface reach equilibrium instantly; and the model which assumes constant charge density on the surface of the particle. The result of numerical simulation reveals that the rate of adsorption of particles onto the surface follows the order (constant surface charge model) > (dynamic model) > (equilibrium model). Under typical conditions, the deviation in the adsorption times of the equilibrium model and the constant surface charge model from the corresponding dynamic model is of the order of 20%. This deviation increases with an increase in ionic strength.