Studies on the mechanism of transport of lanthanide ions through supportedliquid membranes containing di-(2-ethylhexyl) phosphoric acid (D2EHPA) as a carrier

Praseodymium and holmium have been chosen as representative elements of lig ht and heavy lanthanides, respectively, to characterize the extraction reac tions of these elements that are responsible for their separation through s upported liquid membranes (SLM) from nitrate media by using di-(2-ethylhexy l) phosphoric acid (D2EHPA) in kerosene as extractant. in the conditions st udied, it has been demonstrated, the formation of two species that can be d escribed as Ln(NO3)A(2)(HA)(3) and LnA(3)(HA)(2), where Ln represents the l anthanide cation and HA the acidic extractant D2EHPA. These results have be en obtained by using both graphic and numeric treatments of solvent extract ion data. The first one was based on the slope analysis, and the second one , on the use of LETAGROP-DISTR program. The formation constants and relativ e predominance of each species were calculated. A mechanism for the formati on of given species was proposed. (C) 1999 Published by Elsevier Science B. V. All rights reserved.