Evaluation of Italian phillipsite and chabazite as cation exchangers for Ba2+ and Co2+.

The cation exchange properties of Na-exchanged phillipsite and chabazite for Ba2+ and Co2+, two cations present in many nuclear power plants wastewaters, were investigated at 25°C and 0.1 total normality, from either a kinetic or a thermodynamic points of view. Kinetic curves showed a rather fast exchange reaction for both cations, as equilibrium was mostly reached in about one day. Results of 2Na+ ⇄ Ba2+ and 2Na+ ⇄ Co2+ equilibria, interpreted in terms of distribution coefficient (Kd) and separation factor (αBA) and discussed on the basis of the known structural features of the two zeolites, evidenced a moderate to good selectivity of chabazite and phillipsite for Ba, which preludes to possible utilizations of Italian tuffs in the removal of this cation from wastewaters of nuclear origin. On the contrary, selectivity for Co was demonstrated to be very poor.