The release of tritiated water from cobalt(II) exchanged 4A zeolite into surrounding water

Synthetic 4A zeolite has recently been considered as an adsorbent for tritiated waste water. Its sorption capacity is increased, and the speed of release of tritium to surrounding water decreased, if sodium ions in the zeolite lattice are replaced with cobalt(II) ions. The exchange kinetics THO/H2O between Co-A zeolite containing tritiated water and surrounding water has been investigated between 5 deg C and 80 deg C, using cobalt-exchanged 4A zeolite beads of 1.6 and 3.2 mm diameter. The release of THO from Co-A zeolite is a two-step kinetic process which depends on the diffusion of water molecules in the zeolite pores. Kinetic parameters for the diffusion process have been calculated from experimental data and effective self-diffusion coefficients of water in the zeolite beads obtained. The results are compared with corresponding data for other types of zeolite and discussed from the point of view of the practical application of zeolites as adsorbent and storage material for tritiated waste water. (author)