Synthetic inorganic ion-exchange materials—XXIX Ion-exchange equilibria of crystalline antimonic(V) acid with organic cations

Abstract

A study of distribution coefficients as a function of concentration of hydrochloric acid indicates an “ideal” 1:1 exchange reaction for the NH 4 + H + and CH 3 NH 3 + H + systems on crystalline antimonic(V) acid(CSbA). The ion-exchange isotherms have been measured for the NH 4 +, CH 3NH 3 +, C 2H 5NH 3 + · iso C 3H 7NH 3 +, (CH 3) 3NH +, (CH 3) 4N + and (C 2 H 5 N + H + systems on CSbA at 25, 45 and 60°C. The selectivity coefficients vary with the equivalent fraction of the exchanging organic cations. The selectivity sequence decreases in the order, NH 4 + > CH 3NH 3 + > C 2H 5NH 3 + > (CH 3) 2NH 2 + which is parallel to the increasing order of van der Waals dimensions of organic cations. The ion-sieve effect is observed for (CH 3) 4N + and ( C 2 H 5) 4 N + H + systems. The dimension of the window on CSbA lattice can be evaluated to be 5–6 Å. Overall and hypothetical (zero loading) thermodynamic data have been derived for these ion-exchange reactions.