| Boron is an important component of natural and industrial water bodies such as salt lake brine,sea water,nuclear waste water,etc.The study of the thermodynamic properties and phase diagrams of the borate aqueous solution system is extremely important for understanding the crystallization behavior and accompanying thermal changes of these water bodies in industrial processes.In aqueous solution,boric acid molecules?B?OH?3 or H3BO3?and metaborate?B?OH?4-or BO2-?as basic species can form various types of borate?such as triborate,Tetraborate,pentaborate,etc.?.Therefore,in order to understand the complex thermodynamic behavior of borate solution,it is necessary to systematically and comprehensively understand the properties of boric acid and metaboric acid in aqueous solution.However,even for the simplest metaborate-water system,the current knowledge is not comprehensive.In this work,literature data on the phase equilibrium and thermodynamic properties of the MBO2+H2O?M=Li,Na,K?binary system are collected,the specific heat capacity of MBO2?M=Li,Na,K?aqueous solution was measured by Calvet BT2.15 calorimeter,and the solubility of potassium metaborate in pure water at different temperatures was determined by isothermal phase equilibrium method.Most of the literature is inconsistent,and it is basically consistent with Toledano's research results.In addition,using the boiling point method,the vapor pressure of the KBO2 aqueous solution in the temperature range of 314.15 K387.15 K was measured,and the concentration range was from 0.5 to 8 mol·kg-1.Based on the literature data and the experimental data determined in this work,based on the Pitzer-Simonson-Clegg?PSC?semi-empirical activity coefficient equation,a multi-temperature thermodynamic model of the MBO2+H2O?M=Li,Na,K?binary system was constructed.Combined with the multi-temperature thermodynamic model of the metaborate binary system established in this paper and the MCl?M=Li,Na,K?+H2O,M2SO4?M=Li,Na,K?+H2O binary system model in the literature.The solubility of six ternary systems LiBO2+LiCl+H2O;LiBO2+Li2SO4+H2O;NaBO2+NaCl+H2O;NaBO2+Na2SO4+H2O;KBO2+KCl+H2O;KBO2+K2SO4+H2O were simulated,not only for the two the effectiveness of the meta-borate model in the ternary system has been tested,and it has also laid the foundation for the subsequent development of the multi-temperature thermodynamic model for the multi-component boron-containing system. |
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