STUDIES ON SYNERGISTIC EXTRACTION OF SC(I II) WITH HBTMPTP AND CYANEX-925

The synergistic extraction of Sc(III) from H2SO4 solution with bis(2, 4, 4-trimethylpentyl)monothiophosphinic acid(HBTMPTP, HL) and branched chain alkyl phosphine oxide mixture (Cyanex 925, B) in n-hexane has b een investigated, The results indicated that synergistic effect was sh owed in low acidity (c(H2SO4) < 0.25 mol/L). The composition of the ex tracted complex of Sc(III) has been determined to be Sc(HL2)(2)B-3(SO4 )(1/2) by the method of slope analysis, The mechanism of the synergist ic extraction of Sc(III) may be : Sc3+ + 2(HL)(2(O)) + 3B((O)) + 1/2SO (4)(2-)reversible arrow(K12)Sc(HL2)(2)B-3(SO4)(1/2(O)) + 2H(+) ScL(HL2 )(2(O)) + 3B((O)) + H+ + 1/2SO(4)(2-)reversible arrow(beta')Sc(HL2)(2) B-3(SO4)(1/2(O)) + 1/2(HL)(2(O)) Sc(SO4)(1.5)B-2(O) + B-(O) + 2(HL)(2( O))reversible arrow(beta')Sc(HL2)(2)B-3(SO4)(1/2(O)) + 2H(+) + SO42- T heir equilibrium constants have been calculated to be lgK(13)=6.77+/-0 .12, lg beta'=7.71, lg beta '' = 0.10, respectively, The IR spectra an d FAB-MS of the saturated synergistic extraction complex of Sc(III) ha ve been discussed as well.