稀土离子与硫氰酸根及硝酸根的络合作用

COMPLEX FORMATION OF RARE EARTH IONS WITH THIOCYANATE AND NITRATE IONS

在25℃下,以2MNaClO_(4)维持水相的离子强度恒定,用离子交换法测定了除Ce和Pm以外的镧系元素及钇与CNS^(-)和NO_(3)^(-)的络合作用。用北京大学6912计算机处理了实验数据。结果表明:(1)RE^(3+)与CNS^(-)的络合作用不大,当[CNS^(-)]≤1.5M时,主要以RECNS^(2+),RE(CNS)^(2+)及RE(CNS)_(3)三种络合物形式存在;镧系元素与CNS^(-)的络合度Y_((1))随原子序数Z的增大,总的趋向是增大,钇的Y_((1))值为最小。(2)RE^(3+)与NO_(3)^(-)的络合作用较弱,当[NO_(3)^(-)]≤1.5M时,主要的络合物是RENO_(3)^(2+);各镧系元素与NO_(3)^(-)的Y_((1))随Z的增大,总的趋向是减小,钇的Y_((1))值最小。(3)在本实验中,稀土络合离子在树脂上的吸附量是可以忽略不计的。

So far as the authors are aware,the stability constants of the rare earth ions with some inorganic ligands reported in the literature are quite inconsistent with one another.In this paper,the complex formation of all the rare earth ions(besides Ce and Pm)has been studied by ion exchange method at 25℃in NaClO_(4)(2M)ionic medium.The stability constants were calculated by a special computer program written for this purpose in Beida 6912 language.In the case of thiocyanate the complexes were RECNS^(3+),RE(CNS)^(-)RE(CNS)3,but in the case of nitrate,almost only RENO_(3)^(2+).We use Y_((1))to express the ratio(C_(RE)^(0))/(RE^(3+))when(L-)=1M,where(C_(RE)^(0)),(RE^(3+)),(L^(-))represent the concentrations of the total metals,the free metals,and the total ligands respectively.The values of Y_((1))were irregular but had a tendency of increasing with the increase of the atomic number in thiocyanate system and decreasing with the increase of the atomic number in nitrate system.The value of Y_((1))of yttrium was the smallest both in thiocyanate and nitrate systems.