Solvent extraction of lanthanides and yttrium from nitrate medium with CYANEX 925 in heptane

Abstract

The extraction behavior of lanthanides and yttrium usinsg CYANEX 925 (mixture of branched chain alkylated phosphine oxides) in n-heptane from nitrate medium has been studied. The effects of aqueous phase ionic strength, CYANEX 925 concentration in the organic phase, and temperature on Sm 3+ , Nd 3+ and Y 3+ extraction have been investigated. The extractability of the lanthanides and yttrium increases with increasing nitrate concentration, as well as with increasing CYANEX 925 concentration. An extraction mechanism is proposed based on slope analysis. Furthermore, the infra-red spectra of CYANEX 925 saturated with lanthanides are employed to provide evidence of the composition of the complex. The relationship between the logarithm of the distribution ratio and lanthanide atomic number is also discussed which indicates that yttrium can be separated from light lanthanides. In addition separation of the light and heavy lanthanide groups is also possible using CYANEX 925. From the temperature dependence data, the thermodynamic parameters values ( H, S and G) are calculated.  2007 Society of Chemical IndustryKeywords: lanthanides; yttrium; CYANEX 925; extraction mechanism; separation INTRODUCTION CYANEX 925 is a branched chain alkylated phosphine oxide mixture whose structure is:The major component of the mixture is R 2 RP(O) representing approximately 85% of the mixture, while R 3 P(O) represents about 8% of mixture. The physical properties of CYANEX 925 are listed in Table 1. 1 CYANEX 925 has significant advantages as an extractant, such as greater hydrolytic stability and lower aqueous solubility than TBP; 2 a liquid at room temperature and available in a reasonably pure form, eliminating the need for tedious, reagent-consuming purification procedures.3 Because of the spatial steric hindrance effect of the branched chain, the extraction selectivity of CYANEX 925 is superior to CYANEX 923 (consisting of mixtures of R 3 PO, R 2 R PO, RR 2 PO and R 3 PO, R

Solid–liquid extraction of heavy rare-earths from phosphoric acid solutions using Tulsion CH-96 and T-PAR resins

“…Solvent extraction and ion exchange are the common methods used for the recovery and removal of metal ions from aqueous solutions. Literature review reveals that much of work has been done on solvent extraction of rare-earths employing organophosphorus reagents such as di(2-ethylhexyl)phosphoric acid (D2EHPA), bis (2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC 88A), bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302), bis (2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301), alkylated phosphine oxides (Cyanex 921, Cyanex 923, Cyanex 925) and their mixtures [5][6][7][8][9][10][11][12][13] from chloride and nitrate media.…”

Extraction and separation of thorium and rare earths from nitrate medium with p‐phosphorylated calixarene

“…However when the nitric acid concentration is increased, the extraction of Th remains high while that of the REs decreases rapidly, allowing for easy separation. In addition, at higher acid concentrations, the extraction of REs increases with increasing atom number, which is similar to the conventional neutral phosphorus extracting agents such as Cyanex 925 . This behaviour might be explained by the increasing hardness of the lanthanide ions following the increasing atom numbers according to Pearson's principle.…”

Combination of size selective binding ability of 18-crown-6 dissolved in aqueous phase and extractive properties of an amic acid; toward enhancement of rare earths separation

“…A survey on the reported studies confirms that in much of the works concerning on the liquid-liquid extraction of rare earths, organophosphorus compounds such as di(2-ethylhexyl)phosphoric acid, bis (2,4,4-trimethylpentyl)phosphinic acid, 2-ethylhexylphosphonic acidmono-2-ethylhexyl ester, bis(2,4,4-trimethylpentyl)monothiophosphinic acid, bis (2,4,4-trimethylpentyl)dithiophosphinic acid, alkylated phosphine oxides and their mixtures [12][13][14][15][16][17][18][19][20], have been extensively applied as extractant. Although these compounds are known as efficient extractants for rare earth ions, they suffer from incombustibility and they leave phosphorus residues, which are known as environmental menace.…”