Monday, June 18, 2007 - 10:45 AM
The Peregrins (Boise Centre on the Grove)

Separation Potential of Cloud Point Extraction of Lanthanide Salts

Melissa A. Ensor and Ken Nash. Washington State University, Pullman, WA

Cloud point extraction (CPE) has gained increasing attention as a method for the preconcentration of metal ions since it was first introduced in 1973. This environmentally friendly separation process uses a surfactant to selectively concentrate metal-ligand complexes into a smaller volume, surfactant-rich phase (SRP). Both phases are predominantly aqueous, hence the complications associated with the use of organic solvents can be minimized. The surfactant-rich phase is made to partition from the colloidal mixture of polymer and water by means of a simple temperature shift and centrifugation, hence the technique has a significant simplicity of operation. While CPE has been applied successfully to transition metals, only scattered interest has been shown in its application to the lanthanide family. A new method for the extraction of Eu(III) using Triton X-114 and 1-phenyl-3-methyl-4-benzoyl-2-pyrazolin-5-one (PMBP) will be detailed. The effects of NO3-, Cl-, ClO4-, and (CH3)4NCl salts as a function of their concentrations on the extraction efficiency with Eu(III) will be discussed. IR and NMR measurements of the SRP with these salts provide insights into how the structure of the SRP is changed relative to that of purely aqueous systems. One primary objective of this investigation is to better understand the mechanism of the formation of the SRP and the driving forces attendant to lanthanide partitioning between the phases. It has been noted in these studies that PMBP can successfully extract and preconcentrate Eu (III) into the SRP and the extraction efficiency can be maximized using salt additives (salting out).