Ion exchange and membrane potentials in cellulose acetate membranes separating solutions of mixed electrolytes

Theoretical and Experimental Study of the Voltage–Current Characteristic of an Asymmetric Cellulose Acetate Membrane

“…Above this concentration, the membrane rapidly loses the characteristic properties of a cation exchange membrane (c Ն 0.05 M, t 2 Ն 0.5). The above findings are qualitatively in agreement with results reported in the literature for asymmetric CA membranes (10, 28 -30) and homogeneous dense CA membranes (5,9,16).…”

“…This result is consistent with earlier findings (23) that for pH 6 and electrolyte concentrations above 0.02 M, almost all the carboxyl groups of an asymmetric cellulose acetate membrane are ionized. With respect to the carboxyl groups of a homogeneous dense cellulose acetate membrane in NaCl solutions, the same conclusion could be drawn from the experimentally observed pH dependency of the EMF (16). Furthermore, also our experimental results concerning the pH dependency of the small-current resistance (R 0 ) of an asymmetric KP96 membrane reflect this property.…”

“…2, we have applied the equality W i (␦ m ) ϭ W i (ϱ). Equation [16] can also be derived from the expression of the electrochemical potential Eq. [2] by assuming that i (Ϫ␦ 1 ) Ϸ i (␦ m ).…”

Studies on the Electrochemical Characterization of Cellulose Acetate and Dowex-50 Membranes for Uni-Univalent Electrolytes in Aqueous Solutions

“…In such processes ions interact with the membrane, with water, and with each other in a complex fashion (2,3). In order to obtain a more precise characterization of membranes, several authors have found it useful to study electrochemical properties of membranes without (or with neglegible) water flow with the help of emf measurements (i.e., membrane potential) to estimate transport numbers, distribution constant, and density of fixed charges (4,5). Therefore, membrane potentials should most often be used for determination of electrochemical characteristics of the membrane (6,7).…”

Electrochemical Characterization of Cellulose Acetate Membranes. 2. Influence of Casting Conditions and of Thermal Curing of CA-Membranes on the EMF of Concentration Cells with HCl, LiCl, NaCl and KCl Solutions

“…In three previous papers [1,2,3], the transport and Donnan equilibrium properties of a specific dense cellulose acetate (CA) membrane -named "membrane A" in the present paper -were studied by EMF-measuremeiits on concentration cells with CA-membranes separating solutions of HC1, LiCl, NaCl, KC1 and CaCl 2 . The influences of varying background pH and of varying background concentrations of CaCl 2 were investigated.…”