Ion exchange of synthetic zeolite X and Y with Co2+, Ni2+, Cu2+ and Zn2+ ions

Abstract

The ion exchange of the bivalent transition metal ions Co, Ni, Cu and Zn on synthetic NaX or NaY zeolite is studied at 0.01 total normality at 5, 25 and 45°C. In spite of the near identical crystal radius of the 4 ions, there is a marked difference in the exchange isotherms. The maximum loading limits are temperature dependent and are not consistent with the static model of a definite exchange capacity in the big cavities, i.e., 82 % and 68 % in X and Y respectively. The selectivity in the small cages depends on the occupancy and type of ion present in the big cavities and vice versa. The overall selectivity of both X and Y zeolite for bivalent transition metal ions increases in the order Ni < Co < Zn < Cu. In addition to the ion hydration characteristics and ionic radius the exchange is governed by the coordination ability of the transition metal ion.