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本文采用两相滴定法研究α-噻吩甲酰三氟丙酮和甲基膦酸二甲庚酯对三价稀土离子(除P_m、含Y)的协同萃取机理,结果如下: 1.测得HTTA在CCl_4-H_2O(0.1MNa ClO_4)相间的两相电离常数,25±0.5℃时,pK_(aE)=7.63±0.01。 2.起始有机相0.01MHTTA-CCl_4,起始水相10~(-3)M RE~(3+)(0.1MNaClO_4),在25±0.2℃下用P_(350)进行萃取滴定。形成RE(TTA)_3(P_(350))和RE(TTA)_3(P_(350))_2两种类型协萃络合物,它们的稳定常数β_(301)和β_(302)的对数值列于表1。logβ_(301)随镧系元素原子序数的增加而增大,logβ_(302)随原子序数的变化呈现四分组效应。 3.钇形成和镧系元素相同的两种类型的协萃络合物,其稳定常数大小位置均在Ho和Er之间。
In this paper, two-phase titration method was used to study the synergistic extraction mechanism of trivalent rare earth ions (excluding P_m and Y) by using α-thienyltrifluoroacetone and dimethylheptyl methylphosphonate. The results are as follows: 1. CCl_4-H_2O (0.1MNa ClO_4) phase, the pK_ (aE) = 7.63 ± 0.01 at 25 ± 0.5 ℃. 2. Start the organic phase 0.01MHTTA-CCl_4, the initial aqueous phase 10 ~ (-3) M RE ~ (3 +) (0.1MNaClO_4), at 25 ± 0.2 ℃ with P_ (350) extraction titration. Two kinds of coexpressing complexes, RE (TTA) _3 (P_ (350)) and RE (TTA) _3 (P_ (350)) _ 2, were formed and the logarithm of their constants β_ (301) and β_ (302) Listed in Table 1. logβ_ (301) increases with the increase of the atomic number of lanthanides. The log β_ (302) shows a quadruplex effect with the change of atomic number. 3. Yttrium forms two types of coprecipitating complexes with the same lanthanide, both of which have stable constants in size between Ho and Er.