Factors governing the Pu(IV) speciation in solutions

After storage of Pu(IV) hydroxide for more than 4 months, ～90% of this compound polymerizes, the remainder (～ 10%) being weakly polymerized Pu(IV). In 0.01 M NaCl solutions (pH ～4–10) being in equilibrium with mixed or polymeric Pu(OH)₄ (decantates), plutonium is mainly in the form of highly polymerized colloidal particles of molecular weight exceeding 100 kDa. Therefore, the Pu concentration in the solutions prepared by decantation or centrifugation of decanted solutions can range from 10^?4 to 10^?7 M. The content of weakly polymerized Pu in solutions varies from 10^?7 to 10^?9 M and depends on pH of the solution in the range 4–6. This dependence is virtually absent at pH 6–10.