ThF_4-LiCl-KCl熔盐体系中F^-浓度对Th(Ⅳ)电解提取的影响

Effect of F^- concentration on the electrolysis of Th(Ⅳ) in ThF_4-LiCl-KCl molten salt

通过添加Li F和KF调节ThF_4-Li Cl-KCl熔盐体系中的[F^-]/[Th(Ⅳ)]比值,并以[F^-]/[Th(Ⅳ)]比值代表熔盐中F^-浓度大小,研究了F^-浓度对Th(Ⅳ)电解提取率的影响。研究结果表明,在[F^-]/[Th(Ⅳ)]比值为4~12时,Th的提取率呈下降趋势,熔盐中F^-浓度的增加对Th在电极上的析出产生消极影响。用计时电势法研究了不同[F^-]/[Th(Ⅳ)]比值熔盐体系中Th(Ⅳ)的扩散系数,发现[F^-]/[Th(Ⅳ)]比值在4~12时,Th(Ⅳ)的扩散系数呈现先减小后增加的趋势,在[F^-]/[Th(Ⅳ)]比值为8时出现一个拐点;但由于F^-浓度的增加显著降低了Th(Ⅳ)电解过程的电流密度,最终导致相同电解时间内Th的提取率呈下降趋势。

The ratio of [F-]/[Th（Ⅳ）] in the ThF4-Li Cl-KCl molten salt system was adjusted by adding Li F and KF. The ratio of [F-]/[Th（Ⅳ）] reflected the concentration of F-in the molten salt. The effect of F-concentration on the electrolysis recycling rate of Th（Ⅳ） was examined. The recycling rate of Th（Ⅳ） decreased with increasing ratios of [F-]/[Th（Ⅳ）] from 4 to 12, indicating that increased F-concentration in the molten salt affected the precipitation of Th（Ⅳ） on the electrode. Chronopotentiometry was used to determine the diffusion coefficient of Th（Ⅳ） in the Li Cl-KCl molten salt with different [F-]/[Th（Ⅳ）] ratios. The diffusion coefficient of Th（Ⅳ） initially decreased and subsequently increased, and a turning point was observed at a [F-]/[Th（Ⅳ）] ratio of 8. However, due to the increased F-concentration, the current density in the electrolysis process of Th（Ⅳ） was significantly reduced, resulting in a decreased recycling rate of Th（Ⅳ）.