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前言钙与稀土元素的分离,常采用草酸盐和氢氧化物沉淀法,前者由于各个稀土元素草酸盐的络合情况及沉淀的pH值都不同。从镧至镥分离的难易程度有一定的差别。镥钙分离较为容易,镧钙分离相当困难,常需反复操作,才能达到一定的完全度。氢氧化铵沉淀法,选择性较差,加之稀土元素的碱性和氢氧化物的溶解度随原子序数的增大而减小,镧中的钙如果含量大,亦需反复操作分离才能完全。且稀土元素氢氧化物沉淀为胶态,不易过滤。至于用离子交换法分离镧钙,由于淋洗的截取点不易肯定。因此,即使“光谱纯”的氧化镧,也常杂有微量的钙。
Preface The separation of calcium and rare earth elements, often using oxalate and hydroxide precipitation, the former due to the complexation of various rare earth elements oxalate and precipitation pH values are different. There is a certain difference in the ease of separation from lanthanum to lutetium. Calcium separation is easier, lanthanum calcium separation is quite difficult, often required repeated operation, in order to achieve a certain degree of completeness. Ammonium hydroxide precipitation, poor selectivity, combined with rare earth elements and hydroxide solubility with the atomic number decreases, the content of calcium in lanthanum, also need to repeat the operation to separate completely. And the rare earth element hydroxide precipitate is colloidal, difficult to filter. As for the separation of lanthanum calcium by ion exchange method, it is not easy to confirm due to the interception point of rinsing. Therefore, even “spectrally pure” lanthanum oxide is often mixed with traces of calcium.