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研究了用羧基酸的二甲苯溶液从硝酸介质中萃取三价镧系元素和钇。所用试剂是可以在市场上采购得到的羧基酸,例如,Versatic10酸和环烷酸以及已知结构的标准化合物,如,2-二乙基己酸和3-环已基丙酸。此外,对从硫酸盐和氯化物溶液中萃取某些金属也进行了研究。羧基酸的萃取性能与镧系元素原子序数之间的关系表明,其萃取性能与羧基酸分子的位阻大小具有一定的关系。位阻大小可以用位阻参数(即烷基取代基的E_s＇值)确定。对具有空间位阻的酸(-E_s＇>2)而言,从镧到镥,萃取的pH0.5值连续地降低,钇的行为与中间镧系元素(如钆和铽)十分相似。对于直链或其它非位阻酸(-E_s＇<1)而言,中间镧系元素的pH0.5值降到最小值,此后,pH0.5值又再升高。用上述几种酸萃取时,钇的行为与较轻的镧系元素(例如,铈和镨)十分相似。采用斜率分析法对代表轻(镧)、中(钆)和重(镥)稀土金属的萃取化合物的化学配位进行了研究。所用的酸,一种是位阻酸(Versatic10酸;-E_s＇=3.83),另一种是低位阻酸(3-环己基丙酸;-E_s＇=0.28)。试验结果表明,LnA_3(HA)_3型的单聚络合物可以被Versatic10酸萃取,而用3-环己基丙酸时,则按化学配位生成二聚络合物:(LaA_3(HA)_3)_2、(GdA_3(HA)_3)_2以及(LuA_3(HA)_2)_2。对上述两种酸而言,镧系元素在萃取行为上的
The extraction of trivalent lanthanides and yttrium from nitric acid media using a xylene solution of a carboxylic acid was studied. The reagents used are the commercially available carboxylic acids such as Versatic 10 acids and naphthenic acids and standard compounds of known structure such as 2-diethylhexanoic acid and 3-cyclohexylpropionic acid. In addition, the extraction of certain metals from sulphate and chloride solutions has also been studied. The relationship between the extraction performance of carboxylic acids and the atomic number of lanthanides shows that the extraction performance has a certain relationship with the steric hindrance of carboxylic acid molecules. The size of the steric hindrance can be determined using the steric parameter (ie, the E_s’ value of the alkyl substituent). For sterically hindered acids (-E_s’> 2), the pH value of the extraction decreases continuously from lanthanum to acenaphthene, and the behavior of yttrium is very similar to that of the intermediate lanthanides such as gadolinium and terbium. For linear or other non-sterically hindered acids (-E_s’ <1), the pH value of the intermediate lanthanide decreases to a minimum value, after which the value of pH 0.5 increases again. Yttrium behaves much like the lighter lanthanides (eg, cerium and praseodymium) when extracted with the above mentioned acids. The chemical coordination of the extraction compounds representing the light (lanthanum), medium (gadolinium) and heavy (镥) rare earth metals was studied using the slope analysis method. The acids used, one is a hindered acid (Versatic 10 acid; E_s ’= 3.83) and the other is a low hindered acid (3-cyclohexylpropionic acid; E_s’ = 0.28). The results showed that LnA_3 (HA) _3 monomeric complex could be extracted by Versatic10 acid, whereas with 3-cyclohexylpropionic acid, dimerization complex was formed by chemical coordination: (LaA_3 (HA) _3 ) _2, (GdA_3 (HA) _3) _2, and (LuA_3 (HA) _2) _2. For the two acids, the lanthanide is in the extraction behavior