...Janice Littlewood; Samuel Shaw; Pieter Bots; Caroline L. Peacock; Divyesh Trivedi; Ian T. Burke Abstract The incorporation of pertechnetate ( TcO 4 − ) into feldspathoids produced by alkaline alteration of aluminosilicate clays may offer a potential treatment route for 99 Tc-containing groundwater...

... the geosphere as the pertechnetate ion. Much of the Tc is likely to be in the lower Tc(IV) oxidation state due to the low Eh in the near field. Batch Tc(IV) sorption experiments have been performed from pH 3–13, using 95m Tc as a spike, in the presence of quartz, hematite, goethite, plagioclase feldspar, sand...

.... Technetium-99 extraction conditions. Tc extractant † Target compounds Extraction conditions Reproducibility ‡ Reference % Groundwater aqueous pertechnetate 1 h, 6 rpm rotation 1.01 1 mol L −1 CaCl 2 ion exchangeable 2 h, 6 rpm rotation 1.56 1 mol L −1 NaOAc, pH 5 weak...

... of technetium is likely to be dominated by the highly mobile pertechnetate anion ( TcO 4 − ) in aerobic waters, and by Tc(IV), as solid TcO 2(am) , in anaerobic waters ( Cui and Eriksen, 1996 ). The solubility of Tc(IV) in anoxic conditions at high pH above TcO 2(am) , the phase that will most...

.... The following four solutions were prepared to precipitate iron-bearing phases by an electrochemical pro cess: (1) uranyl carbonate [UO 2 (CO 3 ) 2 2− ]: 5 mL of uranyl-nitrate [UO 2 (NO 3 ) 2 2− ] solution were added to 9 mL of 0.5 M sodium carbonate and pertechnetate (TcO 4 − ) solution diluted with tap...

... and analysis of the mineral surface and mineral/fluid interface down to molecular scales, determination of the structures of metal-solution complexes, characterization of the structures of colloidal materials, determination of the mechanisms of sorption of metal ions in solution onto mineral or colloidal...

...J. M. McBeth; J. R. Lloyd; G. T. W. Law; F. R. Livens; I. T. Burke; K. Morris Abstract Iron minerals influence the environmental redox behaviour and mobility of metals including the long-lived radionuclide technetium. Technetium is highly mobile in its oxidized form pertechnetate (Tc(VII...

... probes M any geochemical processes are governed by elementary reactions occurring at the mineral–water interface. Adsorption, ion diffusion, growth, dissolution, precipitation and electron transfer at mineral-water interfaces can change the composition of groundwater, control the geochemical...

.... Trivedi D. Burke I.T. ( 2015 ) Effect of solution composition on the recrystallization of kaolinite to feld-spathoids in hyperalkaline conditions: limitations of pertechnetate incorporation by ion competition effects . Mineralogical Magazine , 79 , 1379 – 1388 . Lord N.S...

... on the adsorption behaviour of the uranyl ( UO 2 2 + ) ion onto the surfaces of both wüstite and portlandite [Ca(OH) 2 ; representative of the expected cementitious phases]. Surface co-ordination chemistry and speciation were determined by ex situ X-ray absorption spectroscopy measurements (both X-ray absorption...

...Mark J. Rigali; Patrick V. Brady; Robert C. Moore Abstract A growing body of research supports widespread future reliance on apatite for radioactive waste cleanup. Apatite is a multi-functional radionuclide sorbent that lowers dissolved radionuclide concentrations by surface sorption, ion exchange...

... uranyl ion (UO 2 2+ ), often in carbonate complexed form (e.g., UO 2 (CO 3 ) 2 2− , UO 2 (CO 3 ) 3 4− , CaUO 2 (CO 3 ) 2 0 ) or as crystalline solids such as metaschoepite (UO 3 ·2H 2 O), uranyl phosphates and uranyl silicates. U(IV) precipitates in reducing environments as uraninite (UO 2...

... from the ion-exchangeable sites, denoted as Fe(II) NH 4 Cl ), sodium acetate-extractable Fe(II) (mainly from the surface complexation sites, denoted as Fe(II) acetate ), and structural Fe(II) (denoted as Fe(II) str ); and (3) to evaluate the reactivity of these Fe(II) species in terms of Tc(VII...

... at the molecular scale. The very important oxidation and related electron transfer reactions, in both air and aqueous solution, are then considered before considering examples of catalysis and functionalization/self-assembly and interaction with organic molecules. In the final section, sorption of metal ions onto...

... so collected have shown that ion exchange, precipitation and dissolution, and surface complexation reactions have occurred between the tank wastes and subsurface sediments, moderating their chemical character and retarding the migration of select contaminants. Processes suspected to facilitate...

... valuable comments. This study was supported by the CH2M Hill Plateau Remediation Company. References Brown D.A. Fulton B.E. Phillips R.E. . 1964 . Ion diffusion: I. A quick-freeze method for the measurement of ion diffusion in soil and clay systems . Soil Sci. Soc. Am. Proc. 28...

... dehydrated, as shown. Reprinted with permission from Bostick et al. ( 2002 ). Copyright 2002 American Chemical Society. In contrast to Cs and Sr, the sorption of redox-sensitive radionuclides is determined by their oxidation state. The negatively charged pertechnetate ion, Tc ( VII ) O 4...

... the role of magnetite in the reduction of soluble oxidants such as Cr(VI). On the other hand, goethite can decrease the transport of many contaminant ions through sorption reactions. Thus, transformation of magnetite to goethite in the Hanford sediments may have altered contaminant migration...

... in the equatorial plane of the uranyl ion and accepted by non-bridging O atoms of sulfate tetrahedra located in the same sheet as the uranyl polyhedron. There are two H 2 O groups in the structure: the one bonded to the uranyl ion, and the other located in the interlayer where it is bonded to K. In the new...

... parameters that better describe the strengths of the bonds within the Np 5+ neptunyl polyhedron. To determine a suitable value of b for Np 5+ neptunyl polyhedra, it is essential that the bond-strength of a Np 5+ neptunyl ion bond be established. To do this, we examined anhydrous Np 5+ neptunyl...