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A Pitzer model for the Na-Al(OH)4-Cl-OH system and solubility of boehmite (AlOOH) to high ionic strength and to 250°C

Chemical Geology

Xiong, Yongliang

In this study, a Pitzer model for the Na-Cl-OH-Al(OH)4 system, and solubility of boehmite (AlOOH) to high ionic strengths, and to high temperatures up to 250°C, has been developed by evaluating equilibrium quotients concerning boehmite in NaCl solutions to 5.0mol·kg-1, and boehmite solubility data in NaOH solutions to ~13mol·kg-1. This model is validated by comparing model-predicted solubilities with solubility data of boehmite in NaOH solutions that are independent from the model development. This model is of value to many fields, including accurate modeling geochemical behavior of aluminum in hydrothermal solutions with high ionic strengths at high temperatures up to 250°C, extraction of aluminum via the Bayer process from various ores, stability of borosilicate glass, aluminum silicate materials as waste forms for long-lived radio nuclides, and bentonite as engineered barrier, in geological repositories.Based on the model developed in this work, solubility of boehmite can be potentially used as a pHm (hydrogen ion concentration on molal scale) sensor/buffer in hydrothermal experiments under neutral to alkaline conditions in NaCl solutions in the absence of silica. This pHm sensor/buffer would enable experimentalists to conduct hydrothermal experiments in a wide range ionic strength under well-controlled pHm conditions. © 2014 Elsevier B.V.

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TYPE Journal Article YEAR 2014
OSTIScopus

Speciation and solubility of thallium in low temperature systems: Additional aqueous and solid thallium species potentially important in soil environments

Speciation Studies in Soil, Sediment and Environmental Samples

Xiong, Yongliang

Thallium has numerous applications in industry. It is also of great environmental concern because of its high toxicity. Therefore, stabilities of its aqueous and solid species under low temperature environments are fundamentally important to its impact on environments. In previous publications (Xiong 2007, 2009), a number of aqueous and solid thallium species and their stabilities were addressed. However, several thallium species that are potentially important to soil environments, especially saline soil environments, have not been covered.

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TYPE Report YEAR 2013
OSTIScopus

Experimental determination of solubility constant of hydromagnesite (5424) in NaCl solutions up to 4.4m at room temperature

Chemical Geology

Xiong, Yongliang

This study reports the solubility constants of both synthetic and natural hydromagnesite (5424) determined in NaCl solutions with a wide range of ionic strength regarding the following reaction:. Mg5(CO3)4(OH)2.4H2O (cr)+10H+⇆5Mg2++4CO2(g)+10H2O(l)Solubility experiments were conducted from undersaturation in deionized water and 0.10-4.4m NaCl solutions at PCO2 of 10-3.4atm and 22.5°C, and lasting up to 1870days. Based on the specific interaction theory, the weighted average solubility constant at infinite dilution calculated from the experimental results in 0.10-3.2m NaCl solutions using the natural hydromagnesite (5424) from Staten Island, New York, is 58.39±0.40 (2σ) in logarithmic units at 22.5°C with a corresponding value of 57.93±0.40 (2σ) at 25°C. Similarly, the weighted average solubility constant using the natural hydromagnesite (5424) from Gabbs, Nevada, is 59.54±0.72 (2σ) in logarithmic units at 22.5°C with a corresponding value of 59.07±0.72 (2σ) at 25°C. The weighted average solubility constant of synthetic hydromagnesite (5424) determined from experiments in 0.10-4.4m NaCl solutions is 61.53±0.59 (2σ) in logarithmic units at 22.5°C with a corresponding value of 61.04±0.59 (2σ) at 25°C. The natural hydromagnesite has lower solubilities because of its higher crystallinity related to their origins than synthetic hydromagnesite. The solubility constant of synthetic hydromagnesite is about one order of magnitude lower than the literature values. The Gibbs free energies of formation at the reference state (25°C, 1bar) are -5896±2kJmol-1, -5889±4kJmol-1, and -5,878±3kJmol-1 for the natural hydromagnesite from Staten Island, New York, from Gabbs, Nevada, and for the synthetic hydromagnesite, respectively. © 2011 Elsevier B.V.

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TYPE Report YEAR 2011
OSTIScopus
Results 101–125 of 139
Results 101–125 of 139
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