ИСТИНА

Supported ionic liquids in separation of platinum metals N.M. Bodnar1, T.M. Buslaeva1, H.V. Ehrlich*2, T.A. Marutina3, P.G. Mingalev2, I.S. Rudik3, S.I. Timakova1 1Russian Techological University, Russia, 2Lomonosov Moscow State University, Russia, 3Vernadsky Institute for Geochemistry and Analytical Chemistry, Russia Supported ionic liquids (SIL) combine the advantages of ion exchange resins and liquid extragents. Chemical attachment of ionic liquids’ molecules to solid support excludes the loss of active component and allows to design new structures which are not possible in solutions. Here we report a new route to SIL via chemical immobilization of a thin layer of short-chain polyethyleneimine (PEI) molecules on silica surface, their crosslinking and quaternization with methyl iodide or benzyl bromide and the use of sorbents thus obtained for extraction and separation of platinum metal ions. We employed for synthesis silica gels with specific surface area 300-400 m2/g and mean pore diameter 10-15 nm, organosilicon compounds for chemical attachment of PEI molecules and PEI with M.w. ~600, thus leading to sorbents with ~1-2 mmol/g content of active nitrogen groups. Sorption experiments conducted in batch and column modes with Pd(II), Pt(II), Pt(IV), Rh(III), Ir(III) and Ir(IV) ions, metal concentration varied in the range 0,01-10 g/l in HCl media (0.1-6 M) with additional Cl- presence up to 100 g/l. Special emphasis we made on the elution of sorbed platinum metals ions, here we tested a large set of eluents, including mineral acids, solution of various salts (NaCl, NH4Cl, Na2SO3, etc.) and solutions of thiourea in HCl, under ambient or elevated temperatures. Sorption of platinum metals ions decreases with HCl concentration, but it is governed really by chloride ions concentration. Binding of platinum metals ions with all sorbents studied proceeds due to anion exchange mechanism, only in the case of Pd(II) sorption on unmodified PEI sorbent complex formation was stated by diffuse reflectance and X-ray photoelectron spectroscopy. Selectivity of binding depends rather on the charge and the size of platinum metal chloride complex than on substituent on nitrogen moiety; affinity decreases in the raw Pt(IV) > Ir(III) > Rh(III) ≈ Pd(II) > Ir(IV) > Pt(II) in 0.1 M HCl and in the raw Ir(III) > Pt(IV) ≈ Rh(III) >> Pd(II) > Ir(IV) > Pt(II) in 6 M HCl. Pd(II) is effectively eluted by ammonia solution, Rh(III) and Ir(IV) – by NH4Cl solution at 80oC, the same for Ir(III) after oxidation to Ir(IV) by chlorine water, Pt(IV) is selectively eluted by thiourea-HCl solutions. Sorbents studied are applied for separation of platinum metals from accompanying metals. e.g., copper and nickel, as well as for isolation of individual platinum metals from their mixtures.