SOLVENT EXTRACTION OF SOME TERVALENT LANTHAN01DS WITH 5-BR0M0-, 3,5-DIBROMO- AND 5-NITROSALICYLALDEHYDE ACETOHYDRAZONES

ABSTRACT

5-Bromo-, 3,5-dibromo- and 5-nitrosalicylaldehyde acetohydrazones (BSAH, DBSAH and NSAH, respectively, or H₂L) were synthesized. The extraction of lanthanoid ions (Ln3+) including praseodymium, europium and ytterbium ions into 1,2-dichloroethane with the synthesized hydrazones in the presence of both tri-n-butylphos-phate (TBP) and perchlorate has been investigated. The extracted species were (Ln³⁺)(HLP⁻)₂(TBP)₃(CI₄ ⁻) for all the hydrazones. The acid dissociation constants, Ka, and the partition coefficients, K_o, of the hydrazones and the extraction constants, K_ex, of the lanthanoid complexes were determined. The introduction of electron-withdrawing bromo or nitro groups to the 3- and/or 5-position of the benzene ring in salicylaldehyde acetohydrazone (SAH), the mother compound of the synthesized hydrazones, was very effective for increasing not only the K_ex value of SAH but also its K_D value and the K_ex values of its lanthanoid complexes. Taking into consideration the above-mentioned three constants, of the synthesized hydrazones DBSAH was the most balanced and recommend-able extractant for the lanthanoids.

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Notes on contributors

Hajime Ishii

To whom correspondence should be addressed.

Fan Yin Heng

On study leave from Department of Chemistry, Liaoning Normal University, 850 Huanghe Road, Dalian, China.