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摘要
The oxidation of UC powder was studied in 0.5-6.0 M HNO3 and HClO4, containing 0.01-0.1 M NaNO2, at ambient temperature. The addition of nitrous acid caused the oxidation potential to exceed 400mV/SCE and thus accelerated the dissolution and increased the dissolution yield to exceed 95%. One hundred percent dissolution at room temperature was achieved within 30 to 40min when 3.0-6.0 M HNO3 was used that contained more than 0.005 M HNO2. The dissolution rate increased with increasing HNO3 concentration and initial solid-to-liquid ratio. The effective dissolution rate constants and reaction orders were estimated for the UC oxidation with H+, NO3- and HNO2 in 0.5-6.0 M HClO4. The rate of UC oxidation with HNO2 exceeded 50-80 times its oxidation rates with NO3- ions. During UC oxidation with HNO2 in 0.5-6.0 M HClO4, 60-85% carbon was oxidized to CO2. The C/U(VI) ratio in the dissolver solution decreased from 0.5 to 0.1 mg eq/mol with increasing of HClO4 and HNO2 solution concentration. Two to five percent of the carbon remained in the insoluble residue of the HNO3 dissolver solutions, even when a 100% U(VI) yield was observed. Scanning electron microscopy of the insoluble residue showed the carbon particle size between 1.0 and 5.0 mu m.
- 出版日期2009
- 单位中国地震局
