Extraction of lead by Cyanex 302 from phosphoric acid media

Lead (II) can be effectively removed from phosphoric acid media by solvent extraction using Cyanex 302. The extraction of lead is strongly dependent o n phosphoric acid concentration. Experimental data have been treated numeri cally by means of the computer program Letagrop-Distr and can be interprete d by assuming the extraction of the species PbR2(HR), PbR2(HR)(2) and PbR2( HL)2, HR being bis(2,4,4-trimethylpentyl)monothiophosphinic acid and HL sta nding for bis(2,4,4-trimethylpentyl)dithiophosphinic acid. The values of th e extraction equilibrium constants at the different phosphoric acid concent rations are also given. Bromley's theory for calculating activity coefficie nts in the aqueous phase has been applied in order to correlate the values of the extraction equilibrium constants with the phosphoric acid concentrat ion.