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 solu tions, by chronopotentiometry to explore the influence of co-ion and counte rion of the exchange group of the membrane, on the transport phenomena. Chl oride, nitrate, sulfate and acetate in sodium salts were used as counterion s and sodium, potassium, calcium and ammonium in chloride salts were used a s co-ions. The membrane showed a potential drop (E-0) in all these electrol ytes 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 t he 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 densit y (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 wit h root r(A) or root r(C) (where r(A) and r(C) are the ionic radii of counte r 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 E lsevier Science B.V. All rights reserved.