LIQUID-LIQUID-EXTRACTION OF GOLD(III) AND ITS SEPARATION OVER COPPER(II), IRON(III) AND ZINC(II) USING THIOUREA DERIVATIVES FROM CHLORIDE MEDIA

Selective liquid-liquid extraction of Au(III) from aqueous chloride me dia (1 mol/L NaCl) into cumene by thiourea derivatives namely 2a-c (N- thiocarbamoylbenzamidine derivatives), 3a-f (N-benzoylthiourea derivat ives) has been investigated in detail. Marked differences in the metal extraction are noted using these organic compounds with respect to th eir structural variation. The extraction behaviour of Au(III) with ext ractants 2a-c and 3a-f followed the order : 2b> 2a>2c and 3e approxima te to 3c approximate to 3d >3a >3f approximate to 3b, respectively. Th e organic reagent 2a and 3c were selected for further detailed studies owing to their better strippability behaviour. Optimum conditions suc h as structure of the organic extractant, aqueous phase pH, diluent, t ime of equilibration, metal concentration, extractant concentration, e ffect of other metal cations were established for extraction separatio n of Au(III). Experimental data have been treated graphically and nume rically by means of the computer programme LETAGROP-DISTR, and can be explained by assuming the formation of the species AuCl3L and AuCl3L2 for 2a-c and AuCl3L2 for 3a-f derivatives. The lack of interference fr om even appreciable amounts of possible base metals such as Cu(II), Zn (II) and Fe(III) may be considered an outstanding advantage of the met hod for separation of gold from these metals using 2a and 3c.