Solubility of transuranium elements and technetium hydroxide compounds in NaOH solutions in the presence of redox and complexing agents
- Inst. of Physical Chemistry, Moscow (Russian Federation)
- Westinghouse Hanford Co., Richland, WA (United States)
The solubilities of hydroxide compounds of Np, Pu, and Tc in the (IV) and (V) oxidation states have been measured in 0.5 to 14 M NaOH solution under non-oxidizing conditions. The solubilities of Np(IV) and Pu(IV) hydrous oxides in the presence of N{sub 2}H{sub 4} increase from 10{sup -8} to 10{sup -5} M at room temperature as NaOH concentrations increase from 0.5 to 14 M. The solubilities of Np(V) and Pu(V) hydroxides are about 100 times higher and increase from 3{sm_bullet}10{sup -5} to 2{sm_bullet}10{sup -3} M as alkali concentrations increase from 1 to 14 M NaOH. In contrast, the solubilities of Tc(IV) and Tc(V) hydroxides (prepared by hydrolysis or chemical reduction) are comparable and about 10{sup -5} M in 1 M NaOH and 10{sup -4} M in 15 M NaOH, 0.05 M N{sub 2}H{sub 4}. The solubility of electrodeposited TcO{sub 2}{sm_bullet}nH{sub 2}O in non-aerated 4 M NaOH is about 6{sm_bullet}10{sup -7} M, substantially lower than that of the hydroxides prepared by hydrolysis or chemical reduction. At fixed NaOH concentrations, complexing agents (CO{sub 3}{sup 2-}, PO{sub 4}{sup 3-}, F{sup -}, C{sub 2}O{sub 4}{sup 2-}, and especially EDTA) or oxidizers (H{sub 2}O{sub 2}, air, O{sub 3}, MnO{sub 4}{sup -}) increase Np(IV), Pu(IV), and Tc(IV) hydroxide solubilities due to complex formation or oxidation. Information on the dissolved and solid forms of Np, Pu, and Tc in the (IV) and (V) oxidation states in alkaline solution are presented.
- OSTI ID:
- 370584
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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