SOLVENT EXTRACTION OF METAL IONSSolvent Extraction and Charge DensitThe !igration o" the !etal ions into the organic #hase occ$rs a"ter the co!#lexation #rocess has occ$rred% The ligands that re#lace the #ri!ar hdration s#here "$rther red$ce the ion charge densit allo&ing the solvation s#here to 'e changed "ro! &ater to the solvent at the inter"ace o" the t&o #hases% ACETYLACETONEAcetylacetone is a weak acid:C5H8O2 C5H7O2 + H+Solvent ExtractionBased on separating aqueous phase from organic phasesed in man! separations" #r" $f" Th" Lanthanides" Ta" N%" Co" NiCan %e a multistage separationCan var! aqueous phase" organic phase" ligandsncomplexed metal ions are not solu%le in organic phase&etals complexed %! organics can %e extracted into organic phaseExtraction 'eaction(hases are mixedLigand in organic phase complexes metal ion in aqueous phaseConditions can select speci)c metal ionsoxidation stateionic radiussta%ilit! *ith extracting ligands(hase are separated&etal ion removed from organic phaseEvaporationBac+ ExtractionSolvent extraction ,n-uence of chemical conditions Solvent Overall extraction" phase splitting &etal ion and acid concentration (hase splitting .istri%ution coe/cient 0&1org20&1aq34d sed to determine separation factors for a given metal ion 'atio of 4d for di5erent metal ions .istri%ution can %e used to evaluate stoichiometr! Evaluation distri%ution against change in solution parameter (lot log 4d versus log 061" slope is stoichiometr! Extraction can %e explained %! complexation sed to determine complexation constants Consider all speciation in aqueous and organic phase&echanism Solvation Extraction of neutral complex O78NO9:7 forms *ith TB( Equili%rium shifts *ith nitrate" %ac+ extraction into aqueous at lo* nitric acid ,on exchange &etal ion exchanged into organic phase" ion transfer in aqueous phase se of organic solu%le acid i;e;" al+!l phosphinic acid 8'7(O7$: ,on pair extraction Charged metal complex *ith extractant of opposite charge i;e;" Ben?o!l>9>meth!l>@>phen!l>A>p!ra?olone;AC,. E6T'ACTANTSolvent extraction is usually applied to the separation or concentration of valuable metal. It is also used to eliminate certain elements which interfere with the recovery of the valuable metal present in the aqueous solution. The extraction of trivalent metal M3+ by the acid extractants (!" is #enerally described by the followin# equilibirum$M(H2O)x3+ (aq) + 3HL (org) ML3(H2O)y (org) + 3H+$Y.'AT,ON OB &ETALSS%&'()ISTI* S+!,'&T '-T(.*TI+& +/ I(+& (III" /(+M S0!/.T' M'1I0M 2% 34%1(+-%50I&+!I&' .&1 676849'&.&T(+!I&'The extraction of iron (III" from sulfate medium usin# 34hydroxyquinoline (!" and 67684phenanthroline (9hen" in chloroform. In the absence of 9hen7 the extraction of the iron (III" at p 6.3: and in 8.8; M