In aqueous mixed-salt solution

Solubility of Carbon Dioxide in Aqueous Mixed-Salt Solutions... 

T he solubility data of gases in aqueous mixed-salt solutions are funda-mentally important in research on liquid-gas mass transfer and in designing gas-liquid contacting operations, especially gas absorption accompanied by chemical reaction. 

The data have, however, been obtained for only a few systems by Onda et al. (J), Joosten and Danckwerts (2), and Hikita et al. (3). These authors also proposed methods for estimating the solubility of gases in aqueous mixed-salt solutions from the corresponding data for each salt in the systems. These studies are extensions of the empirical method proposed by van Krevelen and Hoftijzer (4) on the basis of the following modified Setschenow Equation. 

In the present investigation, the solubilities of carbon dioxide in aqueous mixed-salt solutions were measured at 25°C and 1 atm partial pressure of carbon dioxide, and the possibility of a method for estimating the solubility was discussed. 

In this study, Equation 2 was also used to correlate the solubility data of carbon dioxide in aqueous mixed-salt solutions. The values of A and B, obtained by the least squares method for all the systems, are summarized in Tables V, VI, VII, and VIII. 

In this study, the following equations were developed from Equation 2 to estimate the solubility of carbon dioxide in aqueous mixed-salt solutions from the solubility data in an aqueous solution of each salt component... 

The solubilities of carbon dioxide in aqueous solutions of seven binary and three ternary mixed salts chosen from eight kinds of electrolytes were measured at 25°C and 1 atm partial pressure of carbon dioxide by the saturation method. The experimental results were not correlated easily by the modified Setschenow equation, but they were correlated very well by the empirical two-parameter equation. The parameters in the equation for the binary and ternary solutions could be estimated by assuming an additive rule for the parameters of the component salt systems. This method, therefore, is useful for predicting the solubility of carbon dioxide in aqueous mixed-salt solutions. 

The strong influence of morphology and mixing is well illustrated with the composite particle investigation. These particles were composed of a nickel shell coated on spherical aluminum particles by hydrogen reduction in aqueous metal salt solution. The overall ratio of material in a particle was about 80 wt% Ni and 20 wt% aluminum. With these particles, the ratio of reactants was approximately the same as in the mixed powders, but the morphology of the reactants is radically different. 

Considerable information concerning structural effects on aqueous salt solutions has been provided by studies of the properties of mixed solutions (Anderson and Wood, 1973). In a mixed salt solution prepared by mixing YAm moles of a salt MX (molality m) with Yhm moles of a salt NX (molality m) to yield m moles of mixture in 1 kg of solvent, if W is the weight of solvent, the excess Gibbs function of mixing Am GE is given by (19) where GE is the excess function for... 

Hydrated forms of the hydroxide ion have been much less well characterized though the monohydrate [H302] has been discovered in the mixed salt Na2[NEt3Me][Cr PhC(S)=N-(0) 3]. NaH302.18H20 which formed when [NEt3Me]I was added to a solution of tris(thiobenzohydroximato)chromate(III) in aqueous NaOH. ° The compound tended to lose water at room temperature but an X-ray study identified the centro-symmetric [HO-H-OH] anion shown in Fig. 14.15. The central O-H-O bond is very short indeed (229 pm) and is... 

Horita I, Cole D. R., and Wesolowski D. I (1993b). The activity-composition relationship of oxygen and hydrogen isotopes in aqueous salt solutions, II Vapor-liquid water equilibration of mixed salt solutions from 50 to 100°C and geochemical implications. Geochim. Cosmochim. Acta, 57 4703-4711. 

Table I. Experimental Results of Carbon Dioxide Solubility in Aqueous Binary Mixed-Salt Solutions at 25°C and 1 atm...

Fifth, the fit model has not been tested in mixed-salt solutions and against mineral solubility data (other than gypsum). It is not known whether an ion-association aqueous model, even with additional complexes, will be capable of accurately modeling these systems. 

Figure 5.10 Change in transport number of calcium ions relative to sodium ions of a cation exchange membrane with and without a polypyrrole layer with the concentration of mixed salt solutions in electrodialysis. (A) Cation exchange membrane, NEOSEPTA CM-1 (O) membrane with a polypyrrole layer facing the anode side (X) membrane with polypyrrole layer facing the cathode side. After one surface of the cation exchange membrane (Fe3+ form) had contacted an aqueous pyrrole solution for 4 h, the membrane was immersed in LON hydrochloric acid solution before equilibration with the mixed salt solution used in electrodialysis.

Figure 5.12 Change in transport number of calcium ions relative to sodium ions (PNaCa) and current efficiency of a cation exchange membrane with polyaniline layers on both sides with polymerization time. After the cation exchange membrane, NEOSEPTA CM-1, had been immersed in an aqueous 10% aniline hydrochloride solution for 24 h and then immersed in a 1.0 N ammonium peroxodisulfate solution for various periods, a 1 1 mixed salt solution of 0.250 N calcium chloride and 0.250 N sodium chloride solution (concentration of chloride ions 0.500 N) was electrdodialyzed at 10Acm 2 for 60 min at 25.0 °C.

Note that the concentration product of nitric acid and ammonia in equilibrium with a mixed sulfate-nitrate solution having a value of T = 0.5 is about one-half as high as that in equilibrium with a pure ammonium nitrate solution. The temperature dependence of the partial-pressure product for the aqueous mixed-salt case is similar to that of the pure salt. 

The virial equation approach has also been used for providing an equation of state for aqueous solutes, including electrolytes. In the 1970s, Kenneth Pitzer and his associates developed such equations, which have proven to be quite successful at fitting the behavior of both single- and mixed-salt solutions to high concentrations. This will be treated in more detail in 13.6.3 and Chapter 15. 

Figure 5 shows a typical experimental apparatus used. An aqueous metal salt solution is first prepared and fed into the apparatus in one stream. In another stream, distilled water is pressurized and then heated to a temperature above the desired reaction temperature. The pressurized metal salt solution stream and the pure supercritical water stream are then combined at a mixing point, which leads to rapid heating and subsequent reactions in the reactor. After the solution leaves the reactor, it is rapidly quenched. In-line filters are used to remove larger particles. Pressure is controlled with a back-pressure regulator. Fine particles are collected in the effluent. By this rapid heating method, the effect of the heating period on the hydrothermal synthesis is eliminated thus, specific features of supercritical hydrothermal synthesis can be elucidated. 

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