Cation and anion selectivity of zwitterionic salicylaldoxime metal salt extractants.
3-Dialkylaminomethyl substituted salicylaldoximes are efficient metal salt extractants, and, in contrast to related "salen"-based reagents, are sufficiently stable to acid hydrolysis to allow commercial application in base metal recovery. Crystal structures show that metal salts are bound by a zwitterionic form of the reagents, with copper(II) nitrate, tetrafluoroborate and trifluoroacetate forming [Cu()(2)X(2)] assemblies in a tritopic arrangement with a trans-disposition of the anions outwith the coordination sphere. Copper(II) chloride, bromide and zinc(II) chloride form 1:1 assemblies, [Cu()X(2)], with the halides in the inner coordination sphere of the metal, leading to high chloride selectivity and very good mass transport efficiencies of CuCl(2). Introduction of the anion-binding sites into the salicylaldoxime extractants changes their cation selectivities; the ligands co-extract small amounts of Fe(III) along with Cu(II) from mixed metal aqueous feed solutions, an issue which will need to be addressed prior to industrial application.
Forgan
Ross S
RS
School of Chemistry, University of Edinburgh, Edinburgh, UKEH9 3JJ.
Davidson
James E
JE
Fabbiani
Francesca P A
FP
Galbraith
Stuart G
SG
Henderson
David K
DK
Moggach
Stephen A
SA
Parsons
Simon
S
Tasker
Peter A
PA
White
Fraser J
FJ
D000838:Anions / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010091:Oximes / Q000737:chemistry*; D012492:Salts / Q000138:chemical synthesis / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
D000838:Anions; D002412:Cations; D008024:Ligands; D009942:Organometallic Compounds; D010091:Oximes; D012492:Salts; C005704:salicylaldoxime; D003300:Copper; D007501:Iron; D015032:Zinc