Extraction of Pb(II) by XAD7 impregnated resins with organophosphorus extractants (DEHPA, IONQUEST 801, CYANEX 272)

The aim of this work is to study the extraction of Pb(II) from nitrate solutions (0.1 m) by solvent impregnated resins (SIR). The resins have been prepared by impregnating the amberlite XAD7 using three different organophosphorus extractants namely DEHPA, IONQUEST 801 and CYANEX 272. The impregnation of XAD7 is characterised by a higher affinity for DEHPA than for IONQUEST 801 and CYANEX 272. The adsorption of the extractant has been studied by FTIR which shows that the immobilisation of the extractant results from hydrophobic interaction between the alkyl group of the extractant and the aliphatic chain of the support, and also from other mechanisms like polar or electrostatic forces. Batch sorption studies shows that the sorption of the metal increases with aqueous pH solution and the best sorption efficiency obtained is higher than 95% for DEHPA and IONQUEST 801 in the pH range of 2.75-3 and 3.5-3.75, respectively, and it is about 70% for CYANEX 272 in the pH range 4.5-4.75. An equilibrium model is proposed for the analysis of the distribution data. The extraction of Pb(II) can be explained by the formation of PbL2 and PbNo3L complex in the resin phase in the case of XAD7-DEHPA resin, by the formation of PbL2HL2 and PbNo3L complex in the case of XAD7-IONQUEST 801, and by the formation of the single complex PbLNo3HL in the case of XAD7CY-ANEX 272. The equilibrium constants of these species are also reported. (C) 2004 Elsevier B.V. All rights reserved.