Extraction studies of base metals (Mn, Cu, Co and Ni) using the extractant 2-ethylhexyl 2-ethylhexyl phosphonic acid, PC 88A

The extraction characteristics of the base metals Mn, Cu, Co and Ni have been studied using the extractant 2-ethylhexyl 2-ethylhexyl phosphonic acid (PC 88A). The extraction order of these metals has been established as Mn > Cu > Co > Ni when the loading of the metal in the organic phase is low. On high loading the extraction order is Cu > Mn > Co > Ni. The separation factors beta((Co-Ni)), beta((Cu-Co)) and beta((Mn-Co)) have been determined as a function of loading of the better extracted metal in a pair. The beta((Co-Ni)) and beta((Cu-Co)) have been found to increase with the loading of Co and Cu in the organic phase in Co-Ni and Cu-Co pairs respectively while the beta((Mn-Co)) decreases with the loading of Mn. The extraction orders of these metals and the effect of loading of the metals on the separation factors have been explained on the basis of the following equilibrium reactions: M2++2(HL)(2o)=reversible arrow reversible arrow(?K1)M(HL2)(2o)+2H(+); M2++(HL)(2o)reversible arrow(?K2)ML(2o)+2H(+); ML2o+(HL)(2o)reversible arrow(?K3)M(HL2)(2o) where M represents the metal (Cu, Ni, Co or Mn), (HL)(2) is the dimer of PC 88A, o indicates the organic phase and K-1, K-2 and K-3 are the equilibrium constants of the reactions. (C) 1998 Elsevier Science B.V.