For example, in the field of nuclear waste management, the formation of di-sodium hexaborate tetrahydrate in brines containing magnesium will decrease borate concentrations, making less borate available for interactions with Am(III). The equilibrium constants determined in this study can find applications in many fields. In accordance with the log K 0 for Reaction 1 from a previous publication from this research group, and log K 0 for Reaction 2 from this study, the equilibrium constant for dissolution of di-sodium hexaborate tetrahydrate at 25 ☌ and at infinite dilution, Na 2B 6O 10 In this study, the equilibrium constant (log K 0) for Reaction 2 at 25 ☌ and infinite dilution was determined to be more » –16.44 ± 0.13 (2σ) based on the experimental data and the Pitzer model for calculations of activity coefficients of aqueous species. However, in a 0.1 mol/kg MgCl 2 solution borax dissolves incongruently and is in equilibrium with di-sodium hexaborate tetrahydrate: 2Na 2B 6O 10 According to solution chemistry and XRD patterns, di-sodium tetraborate decahydrate (borax) dissolves congruently, and is the sole solubility-controlling phase, in a 0.01 mol/kg MgCl 2 solution: Na 2B 4O 7 In this paper, solubility measurements were conducted for sodium polyborates in MgCl 2 solutions at 22.5 ± 0.5 ☌. No other data on any Cr(III)-carbonato complexes are available for comparisons. ![]() The log 10 K 0 values of reactions involving these species [ 0.19), respectively. Calculations based on density functional theory support the existence of these species. Only two aqueous species are required to explain Cr(III)-carbonate reactions in a wide range of pH, CO 2(gas) partial pressures, and bicarbonate and carbonate concentrations. The Pitzer ion-interaction approach was used to interpret the solubility data. A combination of techniques (XRD, XANES, EXAFS, UV-Vis-NIR spectroscopy, thermodynamic analyses of solubility data, and quantum mechanical calculations) was used to characterize solid and aqueous species. Extensive studies on the solubility of amorphous Cr(III) hydroxide solid in a wide range of pH (3-13), at two different fixed partial pressures of CO 2(gas) (0.003 or 0.03 atm.), and as functions of K 2CO 3 concentrations (0.01 to 5.8 mol kg -1) in the presence of 0.01 mol dm -3 KOH and KHCO 3 concentrations (0.001 to 0.826 mol kg -1) at room temperature (22 ± 2☌) were carried out to obtain reliable thermodynamic data for important Cr(III)-carbonate reactions. Chromium(III)-carbonate reactions are expected to be important in managing high-level radioactive wastes.
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