The interaction between an aqueous phthalate buffer and the rare earth metal europium(III) was investigated to demonstrate the effect of buffer complexation of Eu on solvent extraction slope analysis. Some literature has suggested the formation of aqueous rare earth-hydroxide complexes in solvent extraction systems due to depressed slopes in log–log plots of extraction data. These claims were made despite the experiments being conducted under acidic conditions where extraction of rare earth-hydroxide complexes cannot affect the acid dependence of the extraction, and despite neglecting to account for aqueous buffer ligand complexation. We investigated the extractant concentration and acid dependencies of the Eu distribution ratio for two bis(2-ethylhexyl)phosphoric acid/o-xylene extraction systems with varying aqueous phase compositions. The first system contained no buffer and produced log–log plots with slopes close to 3, while the second system containing aqueous phthalate buffer resulted in greatly diminished distribution ratio values and acid dependencies with variable slopes. These experiments, in conjunction with fluorescence spectroscopy of the aqueous phases, suggest that the rare earth elements complex with aqueous buffer rather than hydroxide at pH values less than 6.

研究了邻苯二甲酸盐水溶液缓冲液与稀土金属euro（III）之间的相互作用，以证明Eu的缓冲液络合对溶剂萃取斜率分析的影响。一些文献表明，由于提取数据的对数-对数图中的斜率降低，在溶剂提取系统中形成了稀土氢氧化物水溶液。尽管在酸性条件下进行了实验，但稀土氢氧化物络合物的提取不能影响提取液对酸的依赖性，并且尽管忽略了水性缓冲配体的络合，但仍提出了上述要求。我们研究了两种双（2-乙基己基）磷酸/邻苯二甲酸的Eu分配比的萃取剂浓度和酸依赖性-具有不同水相组成的二甲苯萃取系统。第一个系统不包含缓冲液，并产生斜率接近3的对数对数图，而第二个系统包含邻苯二甲酸盐水溶液缓冲液，其斜率可变时，分配比值和酸依赖性大大降低。这些实验结合水相的荧光光谱表明，稀土元素与水缓冲液而不是在pH值小于6的氢氧化物络合。