PNNL

Abstract

The solubility of TcO2•xH2O(am) in the presence of 0.01 M gluconate was measured over a wide range of hydroxide concentrations from pH = 3.5 to 5 M NaOH and as a function of gluconate concentration from 0.01 M to 0.5 M at a fixed hydroxide concentration of pH = 10.5. The presence of gluconate increased the solubility of TcO2•xH2O(am) by approximately two orders of magnitude over most of the pH range compared to the solubility of TcO2•xH2O(s) when no complexant is present. At extremely high hydroxide concentrations, above 3M NaOH, the Tc-gluconate solution species appears to polymerize and then precipitate as a white solid. At a fixed pH of 10.5, increasing the gluconate concentration by two orders of magnitude resulted in only a modest increase in measured Tc concentration. These initial results suggest the Tc-gluconate species may form polymerized species under basic conditions.