Recycling-compatible electroplating of enriched tin-119 targets for the production of antimony-119 for targeted Auger electron therapy

Antimony-119 ( 119 Sb) is a radionuclide of interest for targeted Auger electron therapy. Isotopically pure 119 Sb can be produced by proton irradiation of enriched tin-119 ( 119 Sn) targets in conventional widely available low energy medical cyclotrons. Enriched 119 Sn is very costly (~ 20,000 CAD/gram), requiring recycling of the target material to make this production route economically viable. Herein, we investigate three Sn electroplating methods, evaluate the target quality, as well as method compatibility with subsequent 119 Sb radiochemical purification steps. Three electroplating bath compositions (Sn(II) sulfate, Sn(IV) sols, and Sn(IV) chloride) for Sn deposition were tested and successfully implemented. One of the methods, utilizing a Sn(IV) chloride bath solution was able to achieve quantitative electroplating efficiency (98 ± 3% Sn deposited after 72 h), and an overall post-purification recovery of 84 ± 6% Sn, accounting for losses during the dissolution and purification steps. Moreover, this electroplating bath composition yielded the most homogeneous targets, both with respect to its structure, as well as lack of contaminants and the highest weight percentage of surface Sn (88 ± 2 wt%). All three electroplating baths investigated were able to yield Sn targets of sufficient quality for irradiation, although they showed markedly different surface morphology and surface elemental composition. Sn(IV) chloride bath solution was found to be capable of recycling of 119 Sn as recovered from the 119 Sb purification step. Furthermore, this method yielded the best results in all aspects, displaying the highest homogeneity in surface morphology and elemental composition, which are desirable characteristics for beam tolerance and radionuclidic purity.