| dc.description.abstract | Platinum group metals (PGMs) have received much attention in the fields of industry, geochemistry and medicine. Due to scarcity of PGMs and their high industrial demands, recycling of PGM bearing materials such as industrial wastes, automobile catalytic converters and similar products gained much attention in recent times. Particularly, separation of PGMs as a group from the material bearing the elements followed by their individual separation is crucial. In this study, an attempt was made to develop chromatographic method for separation of individual PGMs (platinum, palladium and rhodium) that are the main constituents of automobile catalytic converters. Anion-exchange chromatography (with mineral acid and organic aqueous solvent containing complexing reagent) and reverse-phase ion-pair chromatography were tried. Rhodium was successfully separated from the other PGMs by using SAX-HPLC, but separation of platinum and palladium was not satisfactory by the tested methods. The main problem lies in a lack of specific detector such as ICP-MS during the time of study. As a result of this, the focus of
the method development switched to solid phase extraction (SPE) technique, in which the effluent from the sorbent is easily collected and analyzed by more suitable detector, ICP-OES. Individual separation of PGMs and their separation as a group from accompanying elements (such as aluminum, chromium, copper and iron) were conducted using different SPE sorbents (SCX-SPE, SAX-SPE, CN-SPE and RP-SPE modified with DOS,) by off-line SPE procedures. The separated analytes from all methods were analysed using ICP-OES. The results from different SPE analysis were compared and discussed. In addition, an attempt was made to recover the retained PGMs from the SPE sorbents using both HCl and HNO3 solutions and percent recovery was calculated. None of the PGMs were retained by SCX-SPE sorbent, but 70,70,72 and 66% of aluminum, iron, chromium and copper was retained respectively. However, it was found that PGMs (except rhodium) were strongly retained on SAX-SPE from dilute HCl, while all accompanying elements did not show any marked retention. Recovery of retained platinum and palladium was also investigated using 1-6 M HCl and HNO3. Nevertheless, both platinum and palladium could not be recovered from SAX-SPE sorbent. Selective separation of palladium from other PGMs and accompanying elements and its quantitative desorption by using 3M HCl solutions was also achieved using CN-SPE sorbent. SPE sorbents modified with 0.19, 0.39 and 0.58 mmol of DOS were studied and compared with regard to their application for separation and recovery of palladium from platinum and rhodium in a medium of HCl solutions. Quantitative retention of palladium was established with 0.58 mmol of DOS. However, recovery of palladium from DOS impregnated RP-SPE sorbent was not successful by using HCl and HNO3 of different concentrations. In the case of platinum and rhodium, the retention was insignificant. | eng |