Résumé
The solvent extraction of rare earths with mixtures of di-( 2-ethylhexyl) phosphoric acid (D2EHPA,H2A2) and sec-nonylphenoxy acetic acid (CA100,H_2B_2) has been carried out. The separation abilities among rare earths were determined and compared with those with D_2EHPA alone. The mechanism of synergistic extraction of lanthanum was discussed. The methods of slope analysis and constant mole were used to examine the extraction stoichiometry. Effects of acidities,concentrations of extractants,and temperature on the extractabilities have been investigated. The results showed that the synergistic effects decrease with increasing atomic numbers of rare earths. At proper ratios of the extractants,the separation abilities of some rare earths with D2EHPA +CA100 were higher than those with D2EHPA alone,which may be applied to the separation of these rare earths. The extracted complex of lanthanum with D2EHPA + CA100 was determined as LaH5A6B2. The synergistic extraction is endothermically driven.