Solubility of technetium dioxide in water and in concentrated salt solution

Technetium dioxide was obtained by thermal decomposition of NH4TcO4 and characterised in terms of crystal structure, grain size distribution and specific surface area. The dissolution experiments were made with 0.1 M NaNO3 solution, saturated NaCl solution, and quinary solution, applying the shaking technique, and the results were evaluated as a function of shaking period, TcO2 amount fed in, pH-value, temperature, and oxygen content. The dissolved Tc thus obtained was by more than 99% TcO4- in the solution. The oxygen content in the solution considerably determines the dissolution rate. Various pH-values result in the formation of different complexes in the various solutions and thus lead to different dissolution rates. The dissolution rate of TcO2 in saturated NaCl solution is three times higher under aerobic conditions than in 0.1 M NaNO3 solution, and in quinary solution it is two times higher. (RB)