三价锕系与镧系元素的有效分离是实现次锕系元素“分离－嬗变”先进核燃料循环的关键之一。以纯化Cyanex 301为代表的二硫代次膦酸对三价锕系与镧系元素具有卓越的萃取分离能力。论文在此基础上开展了二硫代次膦酸的合成、稳定性以及对三价锕系和镧系元素萃取性能研究，并进行了初步的构效关系的探索。论文建立了新的合成方法，合成路线简短、 操作便捷、低毒安全、经济可靠；合成出了3种新的不对称二硫代次膦酸产品，并用红外、核磁、质谱等手段对产品进行了表征。研究了对称和不对称系列的10个二硫代次膦酸化合物萃取分离Am3+和Eu3+的性能，结果表明二苯基二硫代次膦酸和二环己基二硫代次膦酸没有分离能力；其他产品都具有较好的分离能力，但是萃取能力和分离能力大小存在较大差异。不对称的苯基辛基二硫代次膦酸和丁基辛基二硫代次膦酸萃取示踪量Am3+时，Am3+分配比随着pH的升高先增大后减小的现象可以用Am3+与二硫代次膦酸形成8配位萃合物的机理来进行解释，同时也为这一机理提供了新的实验依据。化学稳定性比较研究结果表明，硝酸浓度和温度对二硫代次膦酸的稳定性有显著影响。常温下，与1.0mol/L硝酸接触，二硫代次膦酸稳定性表现都不错。但与3.0mol/L硝酸室温下接触10h，可导致二硫代次膦酸全部分解；60℃与1mol/L硝酸接触10h，二硫代次膦酸分解明显，有的完全分解。总体上，对称二硫代次膦酸的稳定性好于不对称二硫代次膦酸；不对称二硫代次膦酸的两个取代基均为芳香基团时稳定性更好。辐照稳定性比较研究结果表明，辐照剂量为103Gy 时，虽有产品出现分解迹象，但分解率都不大。辐照剂量为105Gy时，分解比较严重，但分解率都在35%以下。总体而言，对称二硫代次膦酸的辐照稳定性要稍高于不对称产品。计算所得的产品分解G值在7～14之间，10个化合物之间没有显著差异。在辐照剂量达到104Gy 时，二硫代次膦酸性能有所下降，但依然能保持较好的萃取分离能力。论文比较研究结果表明，纯化Cyanex 301在萃取分离能力、化学稳定性、辐照稳定性以及辐照之后的萃取分离能力方面表现都很好。综合考虑Cyanex 301是成熟的工业产品，纯化方法简单，可以使用烷烃类稀释剂等因素，纯化Cyanex 301依然是在三价锕系与镧系元素萃取分离中最具应用前景的二硫代次膦酸萃取剂。
The effective separation of trivalent actinides from lanthanides is one of key steps in the advanced nuclear fuel cycle based on minor actinides “partitioning and transmutation”. With purified Cyanex 301 as the representative, dithiophosphinic acids showed the outstanding ability for the extraction separation of trivalent actinides from lanthanides. In the present work, the synthesis of novel dithiophosphinic acids and the extraction of trivalent actinides and lanthanides were studied on the base of previous work. The relationship of structure and extraction performance was explored. The new synthesis route for asymmetric dithiophosphinic acids was successfully established. The route is convenient, low toxic, economical and reliable. Three new asymmetric dithiophosphinic acids were synthesized, purified and characterized by FT IR, NMR and ESI MS. The extraction separation of Am3+ and Eu3+ by 10 symmetrical and asymmetrical dithiophosphinic acids was investigated. The results showed no separation of Am3+ from Eu3+ by diphenyl dithiophosphinic acid and dicyclohexyl dithiophosphinic acid. The other dithiophosphinic acids show obvious but distinct extraction separation performance. The distribution ratio of Am3+ increased at first but then decreased with increasing pH in the extraction of trace amounts of Am3+ by asymmetric phenyloctyldithiophosphinic acid and butyloctyldithiophosphinic acid. This phenomenon could be explained by the extraction mechanism of forming 8-coordination complex between Am3+ and dithiophosphinic acid and viewed as the new experimental evidence for this mechanism.The comparative study of chemical stability showed the significant effect from nitric acid concentration and temperature on dithiophosphinic acid. Dithiophosphinic acids could endure 1.0mol/L nitric acid at room temperature for 24 hours. However, dithiophosphinic acids completely decomposed in 10 hour contact with 3.0mol/L nitric acid. In the contact with 1mol/L nitric acid at 60℃, dithiophosphinic acids were seriously and even completely damaged. In general, symmetrical dithiphosphinic acids have better chemical stability than asymmetrical ones, and the existence of two aromatic groups is favorable for the stability of asymmetric dithiophosphinic acids. In comparative study of radiolytic stability, a few out of 10 dithiophosphinic acids exhibited slight decomposition at the dose of 103Gy. The serious decomposition occurred for all 10 dithiophosphinic acids at the dose of 105Gy but the decomposition percentages were less than 35%. Generally, the symmetric dithiophosphinic acids are a little more stable than the asymmetric ones. The calculated G values for dithiophosphinic acids are between 7~14, not obviously different. Provided with the 104Gy dose of radiation, dithiosphophinic acids were harmed but remained effective concerning the extraction separation performance.The comparative studies in the present work indicate that the purified Cyanex 301 is the excellent one out of 10 compounds because of the good performance in the extraction separation, chemical and radiolytic stabilities and after-irradiation extraction behavior. Considering the advantage of commercial availability, easy purification and using alkane as diluent, the purified Cyanex 301 is still the most promising dithiophosphinic acid extractant for the extraction separation of trivalent actinides from lanthanides.
