Carbon equilibrium solubility

Coprecipitation is a partitioning process whereby toxic heavy metals precipitate from the aqueous phase even if the equilibrium solubility has not been exceeded. This process occurs when heavy metals are incorporated into the structure of silicon, aluminum, and iron oxides when these latter compounds precipitate out of solution. Iron hydroxide collects more toxic heavy metals (chromium, nickel, arsenic, selenium, cadmium, and thorium) during precipitation than aluminum hydroxide.38 Coprecipitation is considered to effectively remove trace amounts of lead and chromium from solution in injected wastes at New Johnsonville, Tennessee.39 Coprecipitation with carbonate minerals may be an important mechanism for dealing with cobalt, lead, zinc, and cadmium. 

Once the spontaneous direction of a natural process is determined, we may wish to know how far the process will proceed before reaching equilibrium. For example, we might want to find the maximum yield of an industrial process, the equilibrium solubility of atmospheric carbon dioxide in natural waters, or the equilibrium concentration of a group of metabolites in a cell. Thermodynamic methods provide the mathematical relations required to estimate such quantities. 

For the calculations, averages of the results of the two 5. -equilibrium models of Ca2+ = 35 p.p.m., Mg2+ = 7 p.p.m., and alkalinity = 1.55 X 10 3 equiv./liter are used. Solubility data of Larson and Buswell (11), carbon dioxide solubility data of Hamed and Davies (2), and the carbonate ionization data of Hamed and Hammer (3) and Hamed and Scholes (4) are used. Linear interpolations are made for dolomite between pK(soly) = 16.3(5°C.) and 17.0(25°C.). Equations outlining the calcite and dolomite calculations are ... 

Strontium sulphate would dissolve in the solution of sodium carbonate in the same manner as it would in pure water until it had saturated the solution, and its solubility product, which is equal to 0.0006 X 0.0006, was reached, but for the fact that long before this could occur the solution would be supersaturated with respect to strontium carbonate, the solubility product of which is only equal to 0.00007 X 0.00007. Thus strontium carbonate is precipitated continuously as strontium sulphate dissolves and since the solution cannot become saturated with the latter as long as a large excess of carbonate ions is present, the solid salt finally remaining will consist entirely of strontium carbonate, provided a sufficient amount of sodium carbonate were employed. The reaction which takes place is, however, reversible, SrSO + Na2C03 SrCOj + NasSO, and, if strontium carbonate were boiled with a solution of sodium sulphate, the solid would change into sulphate until carbonate ions had accumulated in the solution to such an extent as to make the concentration ratio [C03 ] [SO4 ] = 1 74. When this ratio prevails, both solids are in equilibrium with the solution and no change takes place in either direction. 

To determine the diamond equilibrium solubility in the metal melts in a range of its thermodynamic stability we also used a special method which was originally developed early. Based on the data obtained we estimated carbon supersaturations in the melts [4,5]. 

In Figure 3 the equilibrium solubility of naphthalene in toluene expanded with carbon dioxide at 25°C is shown. There is a considerable deviation to the data of Dixon et al [2]. In both works, it was made sure that excess solids were present. Proper filtration of the naphthalene particles in situ prior to sampling is the crucial step of the experiment. Therefore, small amounts of particles leaking through the filter can cause an error in concentration determination. The samples in this work were analysed for naphthalene content by density measurement and additionally by refractive index measurement. The reproducability was better than 0.8 mole percent. 

The results of the adsorption experiments are presented in table 2. The equilibrium solubilities at the same conditions were determined and reported in a previous work [10]. The density values used were those of pure C02 [12] because nimesulide is only a trace component (max. solubility 0.0446 g/1 at 22 MPa). As it can be seen, the sorbate capacity of activated carbon decreases with increasing pressure and density of C02, regarding the values at similar concentrations as well as the total adsorption capacity at saturation concentrations. The higher solvent power of C02 at increasing pressure/density could be an explanation for the adsorption equilibrium shift in direction to lower coverage. 

Although the thermodynamic equilibrium of processes in seawater have been studied for many systems, only two systems of wide interest will be examined (i) the carbonate equilibrium in seawater and (ii) the solubility of Fe(III) in seawater. 

The oceanic carbon pumps (solubility, soft-tissue, and carbonate) are inherently linked. The amount of CO2 dissolved in ocean surface waters is controlled not only by its equilibrium solubility, but also by the relative rates of gas exchange, ocean mixing, and soft-tissue and carbonate production. Nutrients that are necessary for soft-tissue assimilation arrive at the ocean surface with... 

Fig. 4. Equilibrium solubility domains for CaCO and Mg(OH)2 at a total carbonic species concentration of 5 x 10 Af. The shaded areas above the Mg ...

Dissolution of carbonates can only occur if the solution is undersaturated with regard to the solid carbonate. The solubility equilibrium of carbonates and especially of calcite has been discussed extensively in Chapters 4 and 7. 

The equilibrium solubility of Lovastatin in carbon dioxide at 55 C and 75 C and for pressures up to 400 bar was obtained using the HPLC apparatus and reported in Table II and Figure 9. The data exhibit both the abrupt change in solubility above the solvent s critical point, as well as the retrograde behavior, both of which characterize supercritical extraction processes. The solubilities were reproducible to within 5%. 

It is useful to construct a graph relating carbonate mineral solubilities to CO2 pressure. This can be done for calcite starting with equilibrium constant expression (6.2) above. If done rigorously, the derivation accounts for the effects of ion activity coefficients and the presence of CaHCOI and CaCOf ion pairs and of CaOH. Considering all complexation, the exact charge-balance equation for a pure water in which calcite is dissolving is... 

The coastal zone is somewhat anomalous. There, the depth of water is shallow (z < 50m) and the bottom sediments are coarse-grained and low in organic carbon. Because of these factors, the concentration of methane in the water column should be near its atmospheric equilibrium solubility, however the coastal waters receive large amounts of freshwater, which are rich in dissolved methane, thus raising the concentration above that expected from in situ sources along. 

The three Salem samples show increased leaching rates as a function of increased acidity, but not the rate values predicted by simple chemical stoichiometry. A pH decrease from 5.6 to 4.0 is a 39.8x increase in acidity, while a change from 4.0 to 3.0 is a 10x acidity increase. The observed changes were factors of 2.88x and 1.58x, respectively. These discrepancies can be attributed to the complex equilibrium interactions involved in the solubilities of the metal carbonates. These two solubility equilibria are further complicated by the two acid equilibria for the carbonic acid/bicarbon-ate/carbonate system in addition to the equilibrium solubility of congas in water. The solution of these simultaneous equilibria processes to determine the relationship between carbonate solubility and acid concentration is a non-trivial one (sixth degree in concentration). This solubility problem has been approached from several different viewpoints (31-35), the most convenient being a graphical solution of the solubility as a function of initial solution and final solution pH. From this method, it can be theoreti-... 

In the carbonate aquifer system of central Florida, two major controls on the chemical character of the water are solution of calcite and of dolomite. One way to evaluate the significance of these reactions as chemical controls is to determine the departure from equilibrium of the water with respect to each of the minerals. To calculate departure from equilibrium, solubility products of 10 8-35 and 2 X 10"17 were used for calcite and dolomite, respectively. The departure from equilibrium with... 

The maximum value of extract concentration in the supercritical solvent is given by the equilibrium solubility of extractable components in the supercritical solvent. Due to different transport resistances and equilibrium distribution coefficients for different compounds, these may be successively extracted at different rates. The maximum concentration of extract in the supercritical solvent may then be a function of extraction time. A typical example is the extraction of water subsequently to non polar compounds by supercritical carbon dioxide. 

Cheng, M.D. Soriano, A. N. Leron, R.B. Meng-Hui, L. 2010b, Equilibrium solubility of carbon dioxide in the amine solvent system of (triethanolamine+piperazine+water). J. Chem. Thermodynamics, 42, 802-807. 

Figure 1.4 Equilibrium solubilities of rape and soybean oil in liquid carbon dioxide at 25°C as...

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