Publications

Abstract not provided.

Abstract not provided.

In this study, solubility measurements regarding boracite [Mg3B7O13Cl(cr)] and aksaite [MgB6O7(OH)6·2H2O(cr)] from the direction of supersaturation were conducted at 22.5 ± 0.5 °C. The equilibrium constant (log10K0) for boracite in terms of the following reaction, Mg3B7O13Clcr+15H2Ol⇌3Mg2++7BOH4 −+Cl−+2H+ is determined as −29.49 ± 0.39 (2σ) in this study. The equilibrium constant for aksaite according to the following reaction, MgB6O7OH6·2H2Ocr+9H2Ol⇌Mg2++6BOH4 −+4H+ is determined as −44.41 ± 0.41 (2σ) in this work. This work recommends a set of thermodynamic properties for aksaite at 25 °C and 1 bar as follows: ΔHf 0 = −6063.70 ± 4.85 kJ·mol−1, ΔGf 0 = −5492.55 ± 2.32 kJ·mol−1, and S0 = 344.62 ± 1.85 J·mol−1·K−1. Among them, ΔGf 0 is derived from the equilibrium constant for aksaite determined by this study; ΔHf 0 is from the literature, determined by calorimetry; and S0 is computed in the present work from ΔGf 0 and ΔHf 0. This investigation also recommends a set of thermodynamic properties for boracite at 25 °C and 1 bar as follows: ΔHf 0 = −6575.02 ± 2.25 kJ·mol−1, ΔGf 0 = −6178.35 ± 2.25 kJ·mol−1, and S0 = 253.6 ± 0.5 J·mol−1·K−1. Among them, ΔGf 0 is derived from the equilibrium constant for boracite determined by this study; S0 is from the literature, determined by calorimetry; and ΔHf 0 is computed in this work from ΔGf 0 and S0. The thermodynamic properties determined in this study can find applications in many fields. For instance, in the field of material science, boracite has many useful properties including ferroelectric and ferroelastic properties. The equilibrium constant of boracite determined in this work will provide guidance for economic synthesis of boracite in an aqueous medium. Similarly, in the field of nuclear waste management, iodide boracite [Mg3B7O13I(cr)] is proposed as a waste form for radioactive 129I. Therefore, the solubility constant for chloride boracite [Mg3B7O13Cl(cr)] will provide the guidance for the performance of iodide boracite in geological repositories. Boracite/aksaite themselves in geological repositories in salt formations may be solubility-controlling phase(s) for borate. Consequently, solubility constants of boracite and aksaite will enable researchers to predict borate concentrations in equilibrium with boracite/aksaite in salt formations.

Abstract not provided.

Abstract not provided.

Abstract not provided.

The stability constant of FeB(OH)₄⁺ is expected to find applications in many areas of study. For instance, FeB(OH)₄⁺ may have played an important role in transport of ferrous iron in reducing water bodies at the surface of the primitive Earth. In the nearfield of geological repositories, the formation of FeB(OH)₄⁺ can sequestrate soluble borate, lowering borate concentrations available to the formation of the Am(III)-borate aqueous complex.

Abstract not provided.

In this study, solubility measurements on tri-calcium di-citrate tetrahydrate [Ca₃[C₃H₅O(COO)₃]2•4H₂O, abbreviated as Ca₃[Citrate]₂•4H₂O] as a function of ionic strength are conducted in NaCl solutions up to I = 5.0 mol•kg^–1 and in MgCl₂ solutions up to I = 7.5 mol•kg^–1, at room temperature (22.5 ± 0.5°C). The solubility constant (log K$0\atop{sp}$) for Ca₃[Citrate]₂•4H₂O and formation constant (logβ$0\atop{1}$) for Ca[C₃H₅O(COO)₃]^–Ca₃[C₃H₅O(COO)₃]₂•4H₂O (earlandite) = 3Ca²⁺ + 2[C₃H₅O(COO)₃]^3– + 4H₂O (1) Ca²⁺ + [C₃H₅O(COO)₃]^3– = Ca[C₃H₅O(COO)₃]^– (2) are determined as –18.11 ± 0.05 and 4.97 ± 0.05, respectively, based on the Pitzer model with a set of Pitzer parameters describing the specific interactions in NaCl and M_gCl₂ media.

For this study, the interactions of lead with citrate and ethylenediaminetetraacetate (EDTA) are investigated based on solubility measurements as a function of ionic strength at room temperature (22.5 ± 0.5°C) in NaCl and M_gCl₂ solutions. The formation constants (log β₁⁰ ) for Pb[C₃H₅O(COO)₃]– (abbreviated as PbCitrate^–) and Pb[(CH₂COO)₂N(CH2)₂N(CH₂COO)₂)]^2– (abbreviated as PbEDTA^2–) Pb²⁺ + [C₃H₅O(COO)₃]^3– = Pb[C₃H₅O(COO)₃]^– (1) Pb²⁺ + (CH₂COO)₂N(CH₂)₂N(CH₂COO)₂)^4- = Pb[(CH₂COO)₂N(CH₂)₂N(CH₂COO)₂)]^2– (2) are evaluated as 7.28 ± 0.18 (2σ) and 20.00 ± 0.20 (2σ), respectively, with a set of Pitzer parameters describing the specific interactions in NaCl and M_gCl₂ media. Based on these parameters, the interactions of lead with citrate and EDTA in various low temperature environments can be accurately modelled.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.