Transport phenomenon as a function of counter and co-ions in solution: chronopotentiometric behavior of anion exchange membrane in different aqueous electrolyte solutions

Anion exchange membrane has been investigated in different electrolyte solutions, by chronopotentiometry to explore the influence of co-ion and counterion of the exchange group of the membrane, on the transport phenomena. Chloride, nitrate, sulfate and acetate in sodium salts were used as counterions and sodium, potassium, calcium and ammonium in chloride salts were used as co-ions. The membrane showed a potential drop (E-0) in all these electrolytes when a constant current was applied across it, which remained constant for a period less than tau, called the transition time and rose gradually to a maximum (E-max) value. The parameters such as tau, E-0 and E-max and the potential jump (Delta E) and tau and the inflection zone (Delta t) along the time axis have been measured and compared at an applied current density (I) of 10 mA cm(-2) in 10 mM solutions. The values of tau(1/2)/z(A)[A(0)] Or tau(1/2)/z(C)[C-0], With 1/root r(A) or 1/root r(C) E-0 and Delta E with root r(A) or root r(C) (where r(A) and r(C) are the ionic radii of counter and co-ions, respectively) have been correlated. Permselectivity (P) and transference number ((t) over bar(A)) of the membrane with respect to each one of the above electrolytes have been evaluated and discussed. (C) 1999 Elsevier Science B.V. All rights reserved.