Concentrated NaNO.3 solutions

The method and means may be used for welding repair in hard-accessible places of underwater constructions. Seawater may be used as an electrolyte however, in some cases, it is advantageous to use concentrated NaNOs solution in order to accelerate the process of metal anodic dissolution. It is necessary to use the electrolyte flow systems. 

The double-layer influence on the electrode reaction of Zn(II)/Zn(Hg) on DME in NaNOs solutions was studied in the concentration range from 0.01 to 1 M, using dc and ac polarography [30]. The apparent rate constants of the Zn(II)/Zn(Hg) system increase with dilution of the NaN03 supporting electrolyte. However, after the Frumkin correction, the rate constant was virtually independent of the supporting electrolyte concentration. 

For example, 1 retains a high affinity for mercury even in the presence of electrolytes. This is illustrated by the Kd values of Hg " and Cd " ions uptake hy the TiP as a function of sodium nitrate concentration in solution (Fig. 6). The Kd values are very high (>10000 mL g" ) in the presence of a 100-fold excess of the sodium ion. Even higher Kd values were found for cadmium sorption. A gradual decrease in the Kd values as the concentration of NaNOs increases suggests that Hg and Cd " ions are taken up by the ion-exchange mechanism. 

In addition to the aqueous raffinates from the solvent extraction cycles of the Purex process, an actinide bearing waste stream will arise from the washing of the TBP/OK solvent prior to its recycle to the first cycle. These wastes will typically contain actinides in a mixed NajCOs/NaNOs solution which also contains HjMBP and HDBP. The uranium present will form soluble U complexes with carbonate, as discussed in Section 65.2.2.l(i). Carbonate complexation of Pu also leads to solubility in alkaline solutions and in Na2C03 media precipitation did not occur below pH 11.4, although precipitates did form on reduction to Pu One Pu" species precipitated from carbonate media has been identified as Pu(0H)3-Pu2(C03)3 H20. In 2M Na2C03 media, Np is oxidized by air to Np above pH 11.7 while Np either precipitates or is reduced above pH 13. The potential of the Am /Am " couple, in common with those of other actinides, becomes more cathodic with increasing carbonate concentration. In the total bicarbonate plus carbonate concentration range 1.2-2.3 M all the americium oxidation states from (III) to (VI)... 

A model for the nano-structural evolution of Raney-type nickel catalysts (widely used in hydrogenation reactions) from the constituent intermetallic phases present in nickel-aluminium precursor alloys is presented here. Nano-porous nickel catalysts are prepared via a caustic leaching process where the NiAl alloy powder (typically 50-50 at.%) is immersed in concentrated NaOH solution in order to leach away the aluminium present to leave a highly-porous nickel catalyst (often referred to as spongy nickel). 

Figure 2. These curves were calculated with the help of experimentally determined equilibrium constants. Part a Extent of surface complex formation as a function of pH (measured as mole percent of the metal ions in the system, adsorbed or surface-bound). Total ion concentration [TOTFe] = HP3 M (2 X 10 mol/L of reactive sites metal concentrations in solution = 5 X 10 M I = 0.1 M NaNOs. (The curves are based on data compiled by Dzombak and Morel in reference 5. ) Part b Surface complex formation with ligands (anions) as a function of pH. Binding of anions from dilute solutions (5 X 10 M) to hydrous ferric oxide [TOTFe] = 10 M. I = 0.1. (Curves are based on data from Dzombak and Morel in reference 5.) Part c Binding of phosphate, silicate, and fluoride on goethite (a-FeOOH) the species shown are surface species (6 g/L of FeOOH, PT = 10 M, SiT = 8 X JO- M). (Reproduced with permission from reference...

The precipitation process, the reverse of solid dissolution, is dictated by solution thermodynamics. The solution reaches saturation state when the dissolution rate equals the precipitation rate. Nucleation starts when the solution concentration exceeds the saturation concentration. The solution concentration affects the crystallite size of the precipitated catalyst. For example, diluted solution is beneficial to crystal growth due to slow nucleation and the presence of a few nuclei. In contrast, submicrometer- or even nano-sized amorphous gel or sol can be formed starting with a more concentrated solution. 

Figure 10.2. Acid-base speciation of (a) citrate, (b) aluminum, and (c) iron(III) as a function of solution pH at 25°C and in 0.01 mol L NaNOs solutions. The distributions were computed using a total soluble citrate (citys) concentration of 10 mol and total soluble aluminum (Aljs) and iron(in) [Fe(ni)Ts] concentrations controlled by gibbsite (A1(OH)3(x)) and goethite [FeOOH(x)]. (Relevant thermodynamic data from May and Murray, 2000 Baes and Mesmer, 1986 Liu and Millero, 1999.)...

The environmental chemistry of actinide elements at very low solution concentrations (nano-, pico-, or femto-molar), or in association with endemic environmental materials is poorly understood. There is evidence that chemical speciation and transformation of actinide elements in different environments will play a... 

Figure 9 Reported G(H2) and 0(62) as a function of nitrate concentration in 7-radiolysis of HNO3 and NaNOs solutions. (From Ref. 127.)...

Butenhoff, T., Goemans, M., and Buelow, S., (1996), Mass diffusion coefficients and thermal difilisivity in concentrated hydrothermal NaNOs solutions, y. Phys. Chem. 100, 5982-5992. 

A series of experiments to determine cesium distribution using Cs tracer techniques was completed. The distribution of cesium in response to increasing concentrations of NaOH and NaNO at two temperatures, 20 C and 35°C, was examined. Contacting experiments were carried out using an O/A of unity. All contacts were performed in duplicate. The aqueous phase consisted of 0.5 mM CsNOj and varied concentrations of either NaOH or NaNO at 0.01, 0.1, 0.5, 1.0, 2.25, 4.5, and 5.6 M. Cs tracer was introduced at 0.1 pCi/mL aqueous ph ase. The series of 0.5 mM CsNO in NaOH or NaNO solutions were prepared... 

G.6 (a) A chemist prepares a solution by dissolving 4.690 g of NaNO, in enough water to make 500.0 mL of solution. What molar concentration of sodium nitrate should appear on the label (b) If the chemist mistakenly uses a 250.0-mL volumetric flask instead of the 500.0-mL flask in part (a), what molar concentration of sodium nitrate will the chemist actually prepare ... 

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