Irving-Williams series transition metal extraction

As noted already, the extent of extraction depends on the relevant formation constant of the metal or extractant (K,). For metals in the first transition series this will generally follow the Irving-Williams series that is, for divalent metals, V < Cr < Mn < Fe < Co < Ni < Cn > Zn. Thus, unless other factors are involved copper will be extracted at lower pH values than the other elements. In addition it is found that > M+, so that thoriumfTV) will be extracted before iron(III) in turn before copper(II) before sodium. 

As a consequence, the selectivity of extraction of first transition series dications does not follow the Irving Williams order when these reagents are used in base metal recovery. The bis(2-ethylhexyl)ester of phosphoric acid (D2EHPA) shows [1] a preference Zn2+ > Cr21 > Mn2+ > Fe2+ > Co2+ > Ni2+ V2+ which is exploited in the recovery of zinc from primary sources. [69] M2+ ions which form tetrahedral complexes and M3+ ions which show a preference for octahedral donor sets give neutral complexes with 4 1 and 6 1 D2EHPA metal stoichiometries respectively,... 

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