Fei Yuan,Hua Li,Long Li,Shiqiang Wang,Yafei Guo,Tianlong Deng
In this study, densities of the two ternary aqueous solution systems (LiB 5 O 8 + LiCl + H 2 O) and (LiB 5 O 8 + Li 2 SO 4 + H 2 O) were measured using an accurate digital vibrating-tube densimeter from 283.15 to 363.15 K at an interval of 5 K and 101.325 kPa. B 5 O 8 - in aqueous solution was in the form of [B 5 O 6 (OH) 4 ] - . Therefore, the complex aqueous solution of LiB 5 O 8 is in the form of Li[B 5 O 6 (OH) 4 ]. Subsequently, the mean apparent molar volume ( V Φ θ ) and mixing ion-interaction parameters ( θ a , a ′ v and Ψ c , a , a ′ v , c = Li + , a = B 5 O 6 (OH) 4 - , a ′ = Cl - or SO 4 2- ) against temperature were obtained using the Pitzer equation for the first time. And then, the temperature-dependence equations for the Pitzer mixing ion-interaction parameters and the relevant temperature correlation coefficients of the equation a j, i.e. [ f ( a i , T ) = a 1 + a 2 ln( T /298.15) + a 3 ( T − 298.15) + a 4 /(620 − T ) + a 5 /( T − 227)] were also obtained through the least square fitting. These volumetric properties and parameterization Pitzer parameters obtained in this work could hopefully be used for the quantitatively predictive calculation of the physicochemical properties of the mixed electrolytes containing lithium, chloride, and sulfate ions at any temperature.
The dilution enthalpies of LiBO 2 (aq) from 0.0398 to 0.7684 mol·kg −1 and LiB 5 O 8 (aq) from 0.0521 to 0.8067 mol·kg −1 at 298.15 K and 101.325 kPa were investigated using the microcalorimeter BT 2.15. The apparent molar enthalpies on two lithium borates were obtained, and the diagrams of their apparent molar enthalpy against molality for LiBO 2 (aq) and LiB 5 O 8 (aq) were also plotted. Considering the constructers of BO 2 - and B 5 O 8 - in aqueous solution are existed as in [B(OH) 4 ]- and [B 5 O 6 (OH) 4 ]-, the Pitzer single-salt parameters ( β M X ( 0 ) L , β M X ( 1 ) L , β M X ( 2 ) L , C M X L ) for LiB(OH) 4 and LiB 5 O 6 (OH) 4 were obtained for the first time. A comparison between the calculated apparent molar enthalpies for LiBO 2 (aq) and LiB 5 O 8 (aq) based on Pitzer model and those determined experimentally agree well, which indicate that the Pitzer single parameters of LiB(OH) 4 and LiB 5 O 6 (OH) 4 obtained are reliable.
To achieve efficient separation of alkali metal borate resources from the brines of the salt lake to provide a theoretical basis, this paper adopts the isothermal dissolution equilibrium method to study the solid-liquid phase equilibrium and phase diagram of the ternary system (LiB 5 O 8 + KB 5 O 8 + H 2 O) and (LiB 5 O 8 + NaB 5 O 8 + H 2 O) at 288.15 K. The study grasps the changing law of solubility and physicochemical properties of the system, as well as analyses and identifies the solid phase in stable equilibrium. The results show that the stable phase diagrams of the two ternary systems at 288.15 K are of the simple eutectic type, containing one invariant point, two univariate saturated solubility curves, and two crystalline regions. Among them, the crystalline region of LiB 5 O 8 ·5H 2 O is the smallest, indicating that it is not easy to precipitate from the saturated liquid phase, and the density and refractive index curves of each system show regular changes with the increase of LiB 5 O 8 content.
Yuqi Wang,Linxue Yan,Hua Li,Long Li,Yafei Guo,Tianlong Deng
Microcalorimeter measured the dilution enthalpies of the binary systems (LiBO 2 + H 2 O) and (LiB 5 O 8 + H 2 O) at 308.15 K and 0.1 MPa. Based on the Pitzer theory of electrolytes, their apparent molar enthalpies and the Pitzer single electrolyte parameters at 308.15 K were carried out by fitting the experimental data for the first time. Moreover, the calculated apparent molar enthalpies of LiBO 2 and LiB 5 O 8 aqueous solution according to the Pitzer ion-interaction model were consistent well with the experimental values, manifesting the high reliability of this study.
危险品化学品经营许可证（带存储）