Sulphur containing novel extractants for extraction-separation of palladium (II)

摘要

Extraction performance of palladium (II) by sulphur containing extragents has unequivocally established their strong extraction ability toward this thiophilic soft metal. Hence a comprehensive investigative study was initiated by us to examine selective reversible extraction-separation of trace and macro amounts of palladium (II) from both aqueous nitric acid as well as hydrochloric acid media into 1,2-dichloroethane by 1,10-dithia-18 crown-6 (1,10-DT18C6), S(sub 6)-pentano-36 (S(sub 6)-P-36) and bis (2-ethylhexyl) sulphoxide (BESO) dissolved in toluene. From the study of aqueous phase acidity, reagent concentration, period of equilibration, diluent, strippant and diverse ions, conditions are established from its quantitative and reversible extraction. Recovery of Pd(II) from loaded thiacrown and sulphoxide phase is easily accomplished by using sodium thiocyanate, ammonium thiocyanate, thiourea, sodium thiosulphate and mixture of (2M Na(sub 2)CO(sub 3) + 0.5 NH(sub 4)OH) (only for BESO) as the strippants. The lack of interference from even appreciable amounts of contaminants like (sup 137)Cs, (sup 106)Ru, (sup 233)U and (sup 239)Pu may be considered as one of the outstanding advantages of the method. Application of these extractants has been successfully tested for the recovery of palladium from high active waste matrix. The extracted complex from both the thiacrowns has been characterized by elemental analyses and UV-Visible spectra, confirmed to be PdA(sub 2).T (A = NO(sup -)(sub 3), Cl(sup -)) from dilute (pH (approx) 2) acid solutions while composition of organic species with palladium for the sulphoxide, has also been confirmed to be disolvate of the type Pd(NO(sub 3))(sub 2).2BESO. (author). 52 refs., 6 tabs., 6 figs. (Atomindex citation 27:030809)