Np solubility

The chemical components with the most effect on radioelement solubility and sorption were NaOH, NaA102, EDTA, and HEDTA. The EDTA and HEDTA increased Co, Sr, and Am solubility and decreased sorption for almost all radioelements studied. Sodium hydroxide and NaA102 increased Pu solubility and decreased Np and Pu sorption. Sodium nitrite decreased Np solubility, while Na2C03 and HEDTA increased it. These observations give evidence for the formation of radioelement complexes which are soluble and are not strongly sorbed by the sediments near the waste tanks. 

Figure 7 Calculated Np solubilities as a function of pH and Eh in J-13 groundwater variants (Table 5). Np205(g) and Np(OH)4(s) were assumed to be the solubility-limiting phases. Inset shows regions of solubility control versus redox control (shaded area) (Kaszuba and Runde, 1999) (reproduced by permission of American Chemical Society from Environmental Science and Technology 1999, 33, 4433).

Because of its high solubility as NpOJ, the U.S. program considers Np the most hazardous radionuclide for repository times beyond about 10 y (TSPA-95). The threat of Np releases may largely disappear, however, if Np(IV) solids limit Np solubility and the Eh of groundwaters at Yucca Mountain is reduced because of Fe(II) minerals in rock pores, and, or the steady-state release of Np(aq) from spent fuel is at or below 10 (Wilson and Bruton 1989). 

Table 8.1 shows properties and physiological functions of some essential blood plasma proteins used here to study their interaction with gold NPs decorated with citric acid (the most common surface coating for gold NPs since it assists in their synthesis and promotes NPs solubility in water). 

Neptunium is one of the actinides of primary importance because it is most stable in the V oxidation state in which it is most soluble, does not easily sorb on common minerals, and thus is very mobile in the environment. In Fig. 2-8, experimentally measured total Np and Pu concentrations in J-13 water from the Yucca Mountain site are compared with solubility predictions as function of ionic strength. While Ihcory and experiment agree well with each other for Np solubilities, a discrepancy of several orders of magnitude cxi.st between calculated and measured Pu. solubility. Overall, Np. solubility is orders of magnitude higher than that of Pu be-... 

Fig. 2-7. Solution speciation (top) and solid equilibrium phase stability and solubility of Np(V) in concentrated electrolyte solutions (bottom). Under more acidic conditions, chloride increases the solubility of Np(V) whereas the Np solubility converges at increasing carbonate where the Np(V) bisand triscarbonate species predominate.

The pH of an NH3/NH4CI buffer (piQ = 9.24) is sufficient to ensure the precipitation of most metals as the hydroxide. The alkaline earths and alkaline metals, however, will not precipitate at this pH. In addition, metal ions that form soluble complexes with NH3, such as Cu +, Zn +, NP+, and Co +, also will not precipitate under these conditions. 

Uranium tetrachloride [10026-10-5], UCl, has been prepared by several methods. The first method, which is probably the best, involves the reduction/chlorination of UO [1344-58-7] with boiling hexachloropropene. The second consists of heating UO2 [1344-57-6] under flowing CCl or SOCI2. The stmcture of the dark green tetrachloride is identical to that of Th, Pa, and Np, which all show a dodecahedral geometry of the chlorine atoms about a central actinide metal atom. The tetrachloride is soluble in H2O, alcohol, and acetic acid, but insoluble in ether, and chloroform. Industrially the tetrachloride has been used as a charge for calutrons. 

Gcuerally Speaking, pure lavender od is soluble in 2 o to 3 volumes of 70 per cent, alcohol at or under 20°, hut old oils—and rarely even freshly distilled oils, require np to 4 volumes for complete solubility, or... 

Los Alamos is processing a wide variety of residues, including Pu-Be neutron sources, polystyrene-Pu02-U02 blocks, incinerator ash, Pu-U alloys and oxides, Pu-Zr alloys and oxides, Pu-Np alloys and oxides, Pu-Th alloys and oxides, etc. Processes have been developed for these scrap items (see Figure 2), but we need to know more about Pu-Np separations Pu-Th separations oxalate precipitations for both plus 3 and plus 4 valences valence stabilization dissolution methods for high-fired impure oxides in-line alpha monitors to measure extremely low concentrations of Pu and Am in HNO3 solutions and solubility of various mixtures of Pu02 and UO2 under a variety of conditions. 

Balakin KV, Ivanenkov YA, Skorenko AV, Nikolsky YV, Savchuk NP, Ivashchenko AA. In silico estimation of DMSO solubility of organic compounds for bioscreening. J Biomol Scr 2004 9 22-31. 

Mention has already been made of the application of alkoxycyclophos-phazenes, [NP(OR)2] , as flame retardants in rayon. Although the methoxy-derivatives, with their high phosphorus content, were expected to be most efficient in this respect, their water solubility proved a major shortcoming. However, the n-propoxy series, [NP(OPr )2] ( mainly 3—6), were found to impart excellent flame resistance and were well retained by rayon. The cyclophosphazene alkoxides were obtained by the addition of sodium-n-propoxide to the chloride homologues, (NPCl2)n, and were added to the viscose dope before the rayon was spun. The flame resistance imparted by various amino- and thioalkoxy-derivatives was also tested, but found to be inferior to the results obtained with alkoxy-deriva-tives. Several patent applications have resulted from work on this topic. ... 

In the present chapter, we focus on the catalyst nature in solution using well-defined metal NPs as catal 4 ic precursors it means, soluble (or dispersible) heterogeneous pre-catalysts, as stated by Finke [6]. Some experiments described in the literature concerning the distinction between homogeneous and heterogeneous catalysts are discussed (see Section 3), followed by a particular case studied by us with regard to the catalyst nature in the allylic alkylation reaction, using preformed palladium NPs as catalytic precursors (see Section 4). 

Filtration of the catalytic mixture using pore membrane filters or filter aids allows the distinction between soluble and insoluble catalysts. Further catalytic activity analysis from the solution and insoluble residue can give information about the state of the real catalyst. In turn, centrifugation can be appropriated to separate metal NPs from the catalytic solutions, due to their high molecular weight and density, and thus to be separated from molecular species. 

Water solubility, dissociation constant(s) and n-octanol/water partition coefficients allow one to predict how an analyte may behave on normal-phase (NP), reversed-phase (RP), or ion-exchange solid-phase extraction (SPE) for sample enrichment and cleanup. 

DOE. 1995c. Solubility-limited concentrations and aqueous speciation of U, Pu, Np, Am and Tc Comparison between results of Bruno and Sellin (1992) and calculations using GEMBOCHS (version R16). Washington, DC U.S. Department of Energy. NTIS/DE95015124. 

Lemire RJ, Garisto F (1989) The solubility of U, Np, Pu, Th and Tc in a geological disposal vault for used nuclear fuel AECL-10009... 

Metal carbonyl compounds are other suitable precursors for the synthesis of NPs by thermal decomposition. The main advantage is the formation of CO that is expelled from the IL phase due to its poor solubility. However, high temperatures are commonly used to decompose such precursors. Metal NPs of Cr(0), Mo(0), and W(0) were prepared by thermal or photolytic decomposition of their respective monometallic carbonyl compounds [M(CO)6] dispersed in ILs [52]. Similarly, the precursors [Fe2(CO)9], [Ru3(CO)i2], and [Os3(CO)12] were employed in order to obtain stable metal NPs (1.5-2.5 nm) in BMI.BF4 [53]. The same procedure was extended to the preparation of lr(0), Rh(0), and Co(0) NPs in ILs [54]. 

Palladium-catalyzed carbon-carbon cross-coupling reactions are among the best studied reactions in recent decades since their discovery [102, 127-130], These processes involve molecular Pd complexes, and also palladium salts and ligand-free approaches, where palladium(O) species act as catalytically active species [131-135]. For example, the Heck reaction with aryl iodides or bromides is promoted by a plethora of Pd(II) and Pd(0) sources [128, 130], At least in the case of ligand-free palladium sources, the involvement of soluble Pd NPs as a reservoir for catalytically active species seems very plausible [136-138], Noteworthy, it is generally accepted that the true catalyst in the reactions catalyzed by Pd(0) NPs is probably molecular zerovalent species detached from the NP surface that enter the main catalytic cycle and subsequently agglomerate as N Ps or even as bulk metal. 

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