Mixed-salt solutions, solubility carbon dioxide

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

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. 

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

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. 

A detailed description of salt mining will be postponed until the next chapter, but it is important to note that soda ash is made from both limestone and salt, the two major raw materials. As outlined in Fig. 5.2, the brine (salt solution) is mixed with ammonia in a large ammonia absorber. A lime kiln, using technology similar to that discussed earlier, serves as the source of carbon dioxide, which is mixed with the salt and ammonia in carbonation towers to form ammonium bicarbonate and finally sodium bicarbonate and ammonium chloride. Filtration separates the less soluble sodium bicarbonate from the ammonium chloride in solution. 

Barium hydroxide decomposes to barium oxide when heated to 800°C. Reaction with carbon dioxide gives barium carbonate. Its aqueous solution, being highly alkahne, undergoes neutrahzation reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively. Reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble, or less soluble barium salts, may result from double decomposition reaction when Ba(OH)2 aqueous solution is mixed with many solutions of other metal salts. 

Lead-II-hydroxide forms a white powder, which readily absorbs carbon dioxide from the air. The exact structure of Lead-II-hydroxide indicates more of a lead-II-oxide hydrate nevertheless, lead-II-hydroxide is prepared by mixing solutions of sodium hydroxide and lead-II-acetate by adding drop wise, the sodium hydroxide solution into the lead-II-acetate solution. The precipitated lead salt is then quickly filtered-off. Lead-II-hydroxide is insoluble in water, but soluble in dilute acids, and alkali hydroxide solutions. 

The solubility data of carbon dioxide in aqueous solutions of binary mixed salts obtained in this study are summarized in Table I those for ternary mixed salts are summarized in Tables II, III, and IV. Figures 1 and 2 show the solubility data for the potassium chloride-calcium chloride and sodium chloride-sodium sulfate-ammonium chloride mixed solutions, respectively, which are representative of all the data. The salting-out effect was shown in all the systems studied. 

Figure 3 shows the plot for potassium chloride-calcium chloride binary salt system. Figure 4 shows the plot for sodium chloride-sodium sulfate-ammonium chloride ternary salt system. As shown in these figures, the plots of log(L0/L) vs. salt concentration all curve upward convexly, and the effects of these mixed salts on the solubility of carbon dioxide in the aqueous solutions do not show a direct correlation by the Setschenow Equation. These features are the same in all the mixed-salt systems considered here. 

Figure 4. Effect of salt concentration on solubility of carbon dioxide in aqueous sodium chloride (l)-sodium sulfate (2)-ammonium chloride (3) mixed solutions at 25° C and 1 atm...

Supercritical water oxidation Involves mixing chemical agents with water that has been pressurized and heated to a point at which organic compounds become soluble. (Above 705 degrees Fahrenheit, and a pressure above 221 atmospheres, or 3,205 pounds per square inch.) Solution is oxidized at an elevated temperature, producing carbon dioxide and inorganic acids and salts. 

The production cycle starts with the extraction of sodium chloride. About 20% of the world s salt consumption goes into soda ash production [24]. The next step after rock salt mining is the production and purification of brine yielding a concentrated aqueous sodium chloride solution [8,25-27]. A parallel step is the production of carbon dioxide gas by calcination of limestone. The brine is treated with ammonia and carbon dioxide under precipitation of the less-soluble sodium hydrogen-carbonate. Ammonia is recovered by mixing the mother liquor with calcium hydroxide and stripping off the ammonia with steam. Thermal decomposition of sodium hydrogencarbonate yields synthetic soda ash [8,20,22,23,28-38]. The output of soda ash produced by the ammonia-soda process amounts to about two-thirds of the world production [22,23]. 

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