Research on the Solubilities of Sodium Chloride and Sodium Sulfate Under Hydrothermal Conditions
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Research on the Solubilities of Sodium Chloride and Sodium Sulfate Under Hydrothermal Conditions Bo Liu1 · Xin Ding1 · Zhao Jiang1 · Bin Wang1 · Tao Fang1 Received: 28 November 2019 / Accepted: 3 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Salt deposition under hydrothermal conditions can cause serious problems, such as equipment corrosion and pipe blockage. Therefore, the dissolution behavior of inorganic salts in sub-/supercritical water is an important subject. In this paper, a set of fluidity equipment was designed and employed to measure the solubility data of sodium chloride and sodium sulfate in water at 11–15 MPa and 553–613 K. The results show that for sodium chloride, the solubility decreases slightly before the phase transition point and decreases significantly after that. The overall trend of solubility was correlated with water density. For sodium sulfate, in the experimental region investigated, its solubility first increases, then decreases slightly, and finally decreases sharply after passing through the phase transition point. At the same time, six common empirical and semi-empirical models were applied to correlate the solubility data. The results show that the second-order polynomial model and the Cp model lead to relatively satisfactory fitting results for sodium chloride and sodium sulfate, respectively. Then, for the temperature and pressure range investigated, a new correlation model was proposed for obtaining better fitting result. Keywords Solubility · Inorganic compounds · Model correlation · Hydrothermal conditions Nomenclature Abbreviations SCWO Supercritical water oxidation AARD Average absolute relative deviations List of Symbols y Solubility a, b, c, d, k Adjustable parameters Ks Dissolution equilibrium constant AaBb Inorganic salt solute AaBb·zH2O Salt hydrate * Tao Fang [email protected] 1
School of Chemical Engineering and Technology, Xi’an Jiaotong University, Xi’an 710049, China
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Vol.:(0123456789)
Journal of Solution Chemistry
z The number of water molecules in the hydrate C Concentration G Gibbs energy H Enthalpy S Entropy T Temperature R The ideal gas constant cp Specific heat at constant pressure P Pressure N The number of data points Greek Letters 𝛼 Activity 𝜌 Molar density Superscripts exp Experimental cal Calculated Subscripts a, b Number of anions and cations f Fluid phase s Solid phase i The ith substance
1 Introduction Energy and environmental issues have become an important part of the sustainable development of human society. Coal is still one of the main energy sources in China. The coking wastewater generated in the coal industry poses a serious hazard to the environment [1]. Therefore, the coking wastewater must be treated before being discharged into the environment [2, 3]. As a highly efficient, green chemical technology, supercritical water oxidation technology (SCWO) has shown good prospects in the treatment of organic wastewater and has received extensive attention in
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