RadChem 2014

Technetium and Rhenium sulfide nanodispersion size speciation by SAXS, nanosizer and ultramicrocentrifugation.

12 May 2014, 17:15

1h 30m

Gallery (Casino Conference Centre)

Poster Separation Methods, Speciation Poster Session - Separation Methods, Speciation

Speakers

Mr Alexey Safonov (Frumkin"s Institute of Physical Chemistry Russian Academy of Science)Dr Konstantin German (Frumkin"s Institute of Physical Chemistry Russian Academy of Science)

Description

K.E. German1,2, A.A. Shiryaev1, A.V. Safonov1,2, Ya. A. Obruchnikova1,2,3, V.A. Ilin1,2, M.N. Glazkova2, V.E. Tregubova1,2, S.N. Kalmykov4, E.V Abkhalimov1 1 – Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Moscow, Russia 2 – Moscow Medical InstituteREAVIZ, Moscow Russia 3 – Mendeleev Russian Chemical Technology University, Moscow, Russia 4 – Lomonosov Moscow State University, Moscow, Russia Technetium and rhenium heptasulfides were among the first synthesized compounds of these elements as considered the convenient route for Tc and Re separation from aqueous solutions. Although in the first works its composition was established as M2S7 (M = Tc, Re) it was rather surprising in view of Tc and Re redox potentials being in contradiction with those of S2-. No reasonable thermodynamic data is available on the solubility of these compounds mostly due to the variety of chemical nature ascribed to these compounds and difficulties in its nano- and micoro- size speciation/attribution. Only the formation kinetics and colloidal particle size speciation studies [1-3] provided with some reliable information on Tc concentration dependences. Structure unit fragment Tc3S13 for technetium sulfide acc. to EXAFS studies [4] contained trinuclear Tc(IV) cluster with 3-S atom inside it and the planar vacancies filled with multiple disulfide ligands, thus explaining the excesses of S in this compound. In the growing process of Tc-S colloid system, the size of colloid particles was shown to increases by deposition of Tc sulfide on the particle surface, not by coagulation of the particles [3]. Recently mixed oxo-sulfide species of Tc were characterized [5]. Here we continue microcentrifuge size speciation in course of the reaction of Tc(VII) and Re(VII) with sulfide and follow it with size speciation of generated particles in the solution by SAXS at specialized small angle diffractometer SAXSess (Anton Paar (Austia), CuK (1.54 А), transmission analises after collimation correction mode, sealed glass capillaries, registration with ImagingPlate). Based on Log(I) = f(s2) plots, s = 4πsin(Θ)/λ) for the aged samples two types of species were observed in Re sulfide colloidal solution by SAXS. Small particles were monodisperse and quite isotropic with Rg = 0.31 – 0.45 nm. Large particles were disc shaped with 40 nm in diameter and 5 nm height. Both methods supported induction period and kinetic dependent on the [Na2S] in the solution and the order of mixing the reagents. Based on the similarity of chemical behavior we suggest similarity in composition of technetium and rhenium species obtaind in the identical conditions. The stability of M3S10 (M = Tc, Re) in the resulting solution was dependent of the S2- concentration in it. When higher than 0.06M Na2S, further grouth of Tc and Re sulfide particles occurred for  ≥ 150 h similar to observations made in [3]. For [Na2S] ≤ 0.04 M, the M3S10 was reoxidized by present air to Tc(VII) within 175-200 hours thus being resolubilized. The determination of the free Tc and Re species concentration with separation of ionic or nanocolloidal particles with 5 kD “Sartorius” ultramicrocentrifuge tubes gave evidence on the M3S10 nanosulfide formation similar to that observed in [4]. The equation for the Tc sulfide solubility based on these figures was evaluated. References 1. El-Waer, S., German, K. E., Peretrukhin, V. F. J. Radioanal. Nucl. Chem., 157 (1992) 3–14. 2. K.E. German, V.F. Peretrukhin, D.N. Tumanova, A.Yu. Tsivadze. Technetium sulfides – role in chemistry and ecology. In: 7th International Symposium on Technetium and Rhenium – Science and Utilization – Book of Proceedings - July 4 -8, 2011, Moscow, Russia (Eds.: K.E. German, B.F. Myasoedov, G.E. Kodina, A.Ya. Maruk, I. D. Troshkina). Publishing House GRANITZA, Moscow 2011, p. 181-186. 3. Y. Saiki, M. Fukuzaki, T. Sekine et all. J. Radioanal. Nucl. Chem. 255 (2003) 101–104. 4. W. W. Lukens, J. J. Bucher, D. K. Shuh, N. M. Edelstein