Effect of inorganic ligands and hydrogen peroxide on ThO2 dissolution. Behaviour of Th0.87Pu0.13O2 during leaching test.
Effect of inorganic ligands and hydrogen peroxide on ThO2 dissolution. Behaviour of Th0.87Pu0.13O2 during leaching test.
复制标题
无机配体和过氧化氢对 ThO2 溶解的影响。
作者：
S. Hubert;G. Heisbourg;N. Dacheux;P. Moisy
在不同pH值和不同阴离子浓度条件下，考察了ThO 2粉末样品的溶出情况。本文的第一部分描述了pH值对ThO_2在硝酸和盐酸介质中溶解的影响。相对于质子浓度和表观归一化溶解速率常数的偏序进行了测定。本文的第二部分描述了其他配体，如高氯酸盐，氯化物，硫酸盐和过氧化氢的溶解动力学（在pH 1）的影响。RL的增加与配体与Th的络合亲和力的增加相关。虽然硝酸盐和盐酸介质，这是弱络合，导致RL值与那些高氯酸盐介质相同的数量级，硫酸盐或过氧化物的存在下，在浸出液中显着提高溶解的ThO 2。因此，溶解机制可以解释为通过在固/液界面处形成表面复合物来削弱Th-O键，这增强了脱离，从而加速了全局溶解。此外，还研究了Th_（0.87）Pu_（0.13）O_2固溶体的溶解。Th 0.87 Pu 0.13 O2的溶解动力学比Th O2的溶解动力学大，这可能是由于浸出液辐解生成的过氧化氢的存在所致。此外，钚在酸性介质中的氧化还原性质，如Pu（IV）和Pu（V）的还原和Pu（VI）和Pu（IV）在Pu（III）中被H2 O2还原，可能增加钚的溶解。
The dissolution of ThO2 powdered samples was examined in various conditions of pH and concentration of anions in the leachate. The first part of this paper describes the influence of pH on the dissolution of ThO2 in both nitric and hydrochloric media. The partial order relative to the proton concentration and the apparent normalized dissolution rate constants were determined. The second part of the paper describes the influence of other ligands such as perchlorate, chloride, sulfate, and hydrogen peroxide on the dissolution kinetics (at pH 1). An increase of RL was observed correlatively with the increase of complexing affinity of the ligand with Th. While nitric and hydrochloric media, which are weakly complexing, lead to RL values with the same order of magnitude as those for perchlorate media, the presence of sulfate or peroxide in the leachate significantly enhances the dissolution of ThO2. Consequently, the dissolution mechanism can be explained by the weakening of Th-O bonds through the formation of surface complexes at the solid/liquid interface, which enhance the detachment and thus accelerate the global dissolution. In addition, the dissolution of Th 0.87Pu 0.13O2 solid solution was also examined. The increase of the dissolution kinetics of Th 0.87Pu 0.13O 2, in comparison with that of ThO2, is considered to be caused by the presence of hydrogen peroxide formed by radiolysis of the leachate. Moreover, the redox properties of plutonium in acidic media, like disproportionation of Pu(IV) and Pu(V) and reduction of Pu(VI) and Pu(IV) in Pu(III) by H2O2, probably increase the dissolution of plutonium.