Transient behaviors of interacting electrical double layers

 The unsteady-state potential and space charge distributions between two identical, planar parallel charged surfaces immersed in an a:b electrolyte solution are examined theoretically. The effects of the ratio of the diffusivities of counterions and coions, D _con/D _co, the mean diffusivity (D _con D _co)^1/2, and the separation distance between two surfaces, H, on the transient distributions of electrical potential and space charges are investigated. The result of numerical simulation reveals that the extent of a system to reach its new equilibrium state depends largely on the magni-tude of a scaled time ν(=Dtκ²). For a fixed H, the greater the value of ν, the closer a system to its new equilibrium state. For constant H and ν, the smaller the ratio (D _con/D _co), the greater the deviation of a system from its new equilibrium state. In addition, the effect of D _con on this deviation is greater than that of D _co. Received: 3 September 1997 Accepted: 16 October 1997