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

Abstract

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 NH 4SCN and an organic phase containing 100–300 kg m −3 Primene JMT or TOA, (RNH 3 +·SCN −) o and (R 3NH +·SCN −) o were formed with apparent equilibrium constants, log K ex,a, of 8.7 and 6.5, respectively. The extraction of 1×10 −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( RNH 3 +· SCN −) o + Ag( SCN) 3 2− = K ex,3 (( RNH 3 +) 2· Ag( SCN) 3 2−) o +2 SCN −, logK ex,3 =1.6 2( R 3 NH +· SCN −) o + Ag( SCN) 3 2− = K ex,3 (( R 3 NH +) 2· Ag( SCN) 3 2−) o +2 SCN −, logK ex,3 =2.5.