Extraction of Ag(I) from aqueous thiocyanate solution with Primene JMT or TOA

Using Primene JMT or TOA, the extraction of thiocyanic acid and of Ag(I) thiocyanato-complex from aqueous thiocyanate solution was studied. On extraction of thiocyanic acid using aqueous phase containing 1.0 M NH4SCN and an organic phase containing 100-300 kg m(-3) Primene JMT or TOA, (RNH3+ SCN-)(o) and (R3NH+.SCN-)(o) were formed with apparent equilibrium constants, log K-ex.a, of 8.7 and 6.5, respectively, The extraction of 1 x 10(-3) M Ag(I) from aqueous ammonium thiocyanate solutions by the thiocyanate salts of Primene JMT or TOA at concentrations ranging from 100 to 300 kg m(-3), and in the presence of ammonium thiocyanate at concentrations of 0.5-3.0 M can be summarized as follows: 2(RNH3+.SCN-)(o) + Ag(SCN)(3)(2- Kex,3) = ((RNH3+)(2).Ag(SCN)(3)(2-))(o) + 2SCN(-), logK(ex,3) = 1.6 2(R3NH+.SCN-)(o) + Ag(SCN)(3)(2-) (Kex,3) = ((R3NH+)(2).Ag(SCN)(3)(2-))(o) + 2SCN(-),logK(ex,3) = 2.5. (C) 2000 Elsevier Science B.V. All rights reserved.