SORPTION CONCENTRATION OF PLATINUM GROUP METALS FROM NITRATE SOLUTIONS

摘要

At processing of some kinds of wastes (electronic scrap, secondary materials, spent nuclearfuel) in nitric acid solutions, and also in technology of silver refining, the significant amountsof palladium and platinum passes into a solution. The ion-exchange concentration ofpalladium and platinum in nitric acid solutions (5-500/dm~3) are investigated. More than 30various classes of ionites are tested. The most chemically resistance resins at the givenconditions are identified. It is shown, that the maximum sorptive capacity to studied metals athigh acidity the complexing, synthetic and inorganic sorbents possess. To definition ofplatinum metals sorption optimum conditions the kinetics is studied, isotherms of a sorption atvarious parameters from nitrate solutions are obtained. The conditions of the platinum and apalladium desorption from the pregnant sorbents and its regeneration with the subsequentreuse of materials were defined.The raw materials containing precious metals have very diverse composition and physicalproperties. Commonly the materials are processed by hydrometallurgical way. If gold orPGMs there are in raw materials to its opening hydrochloric acid solutions are applied. As anoxidizer nitric acid, hydrogen peroxide, gaseous chlorine, etc are used. Nevertheless, atprocessing of argentiferous materials and preliminary treatment of a waste including the spentnuclear fuel, nitric acid solutions are often used and the specified metals in some extent passinto solution [1]. Therefore selective extraction of PGMs from nitrate solutions is an actualproblem.In the present work the ion-exchange concentrations of palladium and platinum in nitric acidsolutions (5-500 g/dm3) are investigated. At the testing more than 30 various classes of ionitesthe most chemically resistance resins at the given conditions are identified. These resins aresynthesized on the base of polyacrylate, styrene-divinylbenzene and vinylpyridine.For a selection of the most effective resin among what are made in Russia and overseas, anumber of ionites with various functional groups were studied. Influence of functional groupstype on a PGM sorption is shown for extraction of a palladium as an example (table 1).The presented data shows, that palladium concentration in a phase of ionites depends onsorbent type. If the increasing of solution acidity essentially reduces palladium sorption bysulfonic cation-exchange resins (KU-2×8) than its sorption by strongly basic anionites isapproximately equal. Intermediate position is occupied by complexing sorbents. The latter(AN-31, SN-3, ANKB-35, Lewatit TP 207, Purolite S 930) are the most effective forextraction of PGMs from nitrate solutions from the point of view of capacity value.According to [2], solution behavior of Pt (II) and Pd (II) are similar. As is known fromcoordination chemistry, ligand environment of the metal ions substantially impacts tocharacter of electronic spectra. The figure 1 shows the results of measurements of opticaldensity of platinum bearing solutions with various concentration of nitric acid at λ=400nanometers.