SPONTANEOUS ELECTROCHEMICAL SEPARATION OF CARRIER-FREE COPPER-64 AND COPPER-67 FROM ZINC TARGETS

Electrochemical processes are attractive techniques for the separation of electropositive metal ions. In this paper, we describe the first application of the spontaneous electrodeposition technique for the separation of carrier-free radioisotopes of copper from proton- or neutron-irradiated zinc targets. The unique feature of this process is the deposition of copper on the Pt electrode without the requirement of an external electromotive force (EMF). The deposited radioactivity is then easily removed from the electrode material yielding highly pure preparations of carrier-free Cu-64 or Cu-67. Separation factors which have been achieved exceed those reported for other processes. The process is intrinsically simple with a minimum of manipulation and therefore amenable to automation and remote processing. The deposition process was found to be rather insensitive to the concentrations of ZnSO4 and H2SO4. The evaluation of the kinetics of the electrodeposition of carrier-free Cu-67 yielded a deposition velocity of (1.50 +/- 0.27) x 10(-1) min-1 corresponding to a deposition constant of approximately 0.77 cm . min-1. Under our experimental conditions, the deposition process was found to be largely irreversible. From the temperature dependence of the deposition velocity constants, an activation energy of 0.18 +/- 0.03 eV was calculated. Furthermore, it appears that the thermodynamic spontaneity is satisfied at all concentrations of copper ions.