Estudio de la extracción de tierras raras ligeras a partir de la extracción líquido – líquido utilizando ácidos organofosforados y ácido ascórbico

摘要

The Liquid – liquid extraction (LLE) or solvent extraction (SX) is the most widely technique used to separate the Rare Earth Elements (REEs). The saponification of the extractants has been used as an efficient practice to promote this separation, however this process produces wastewater containing ammonia – nitrogen, sodium, magnesium or calcium ions that must be removed from solution otherwise could cause environmental pollution. There is a concern about separating efficiently rare earth elements by alternative methods to saponification. The use of complexing agents, such as ascorbic acid, may be used as an alternative to maintain the efficiency of the separation process and without causing any harm to the environment because it is a biodegradable substance. This study aimed to evaluate the influence of ascorbic acid concentration over lanthanum and didymium (Pr + Nd) extraction by liquid – liquid extraction. Three acids organophosphorus extractants were used (D2EHPA, P507 and Cyanex272). The experiments showed that, the increase in the ascorbic acid concentration enhances the extraction and selectivity of the extraction of REEs. It was also determined that the more efficient extractant in the conditions of this study was P507. We considered that the best conditions to perform the separation between La / didymium was obtained with P507 as extraction agent P507 and concentration of ascorbic acid 0.5 mol·L -1 . In this condition the extractions of La, Pr and Nd were obtained equal to 12.3 ± 1.3%, 56.4 ± 1.0%, 64.8 ± 1.7%, respectively, as well as a separation factor of 9.3 ± 0.8 and didymium in organic phase with 81.4 ± 0.5% purity.