Europium lanthanide extraction

The analysis of the extraction by CPo21 data reveals a 1 1 metal ion-to-ligand ratio for europium and thorium. The selectivity factors indicate a good selectivity toward these two cations with respect to Mn2+, Pb2, Cd2+, Fe2+, Ni2+, and Co2+, among which only cadmium is a weakly radioactive fission product.155 A synergistic extraction of almost three orders of magnitude was evidenced for the extraction of La3+, Nd3+, Eu3+, Ho3+, Lu3+ with 4-benzoyl-3-methyl-l-phenyl-5-pyrazolone and CPo21 however, it does not improve the separation factors between lanthanides.156... 

A mixture of well-known extractants, di-(2-ethylhexyl)phosphoric acid (HDEHP) and CMPO, in n-paraffin was used for the study of combined extraction of different actinides (americium, plutonium, and uranium) and lanthanides (cerium and europium) and their separation from fission products (cesium, strontium, ruthenium, and zirconium).54 Combined extraction of MAs and lanthanides was studied together with group separation of MAs from lanthanides by selective stripping with a solution of diethylenetriaminepentaacetic acid (DTPA), formic acid, and hydrazine hydrate. This solution strips only MAs, leaving lanthanides in the organic phase. Subsequently, the lanthanides are stripped using a mixture of DTPA and sodium carbonate. 

As a metal, europium is very reactive so that one usually finds it under its trivalent, triply oxidized form (Eu3+ ion) in oxides or salts. A divalent form (Eu2+) also displays some stability. Two minerals that contain many of the lanthanide elements, which are separated by liquid-liquid extraction, are commercially important monazite (found in Australia, Brazil, India, Malaysia, and South Africa) and bastnasite (found in China and the United States). 

Although Rhone-Poulenc has given up direct upstream development after fruitless association with Dysan in magnetic supports and Siltec in silicon, it still believes it can use its know-how in rare earths to develop their electronics applications. Today, Rhone-Poulenc is the indisputable leader in rare earths, accounting for 40 percent of the world market. At its units in La Rochelle, France, and Freeport, Texas, it is capable of extracting from lanthanide sands the fourteen elements they contain. Over the last few years, samarium, for instance, has become essential for microelectronics to the same degree that europium and yttrium oxides already are for color television. 

Tridentate N-donor ligands are efficient in separating actinides from lanthanides selectively by solvent extraction, an area of potential great importance in treatment of used nuclear fuel rods. The tridentate ligand 2,2 6 ,2 -terpyridyl (terpy) forms a range of complexes. The perchlorate complexes [Ln(terpy)3] ( 104)3 contain nine-coordinate cations with near- )3 symmetry, a structure initially deduced from the fluorescence spectrum of the europium compound (Section 5.4) and subsequently confirmed by X-ray diffraction smdies (Figure 4.7)... 

In the various solvent-extraction circuits employed in this process, use is made of a solution of D2EHPA in kerosene as the extractant. The selective recovery of the various metals is achieved by careful control of the equiUbrium pH value of the aqueous phases in the multistage extraction and stripping operations. After the leach liquor has passed through two separate circuits, each of which comprises five stages of extraction and four of stripping, the europium product is obtained initially as a solution of europium(III) chloride. Further purification of the product is accomplished by reduction with amalgamated zinc to Eu +, which is by far the most stable of the divalent lanthanide ions with respect to the reduction of water cf. the redox potentials of the Eu /Eu and Sm /Sm + couples, which are —0.43 and —1.55 V respectively ). Sulfuric acid is added to the... 

The lanthanides are separated from most other elements by precipitation of oxalates or fluorides from nitric acid solution. The elements are separated from each other by ion-exchange, which is carried out commercially on a large scale. Cerium and europium are normally first removed, the former by oxidation to Celv and removal by precipitation of the iodate which is insoluble in 6M HN03 or by solvent extraction, and the latter by reduction to Eu2+ and removal by precipitation as insoluble EuS04. 

Lanthanide metals were also successfully extracted from their oxides with a high pressure mixture of TBP-HNO3-H2O-CO2 (12). We applied this technique to extract europium from the additives contained in fluorescence light tubes. The additives were recovered as white powder by crashing the glass tubes. An experimental study was performed with a similar apparatus as shown in Figure 6. The results of extraction of europium are given in Table 1 as well as the experimental conditions. In Ref. (12), the recovery yield approached 100% easily, but relatively low recoveries... 

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