Article pubs.acs.org/jced
Solid−Liquid Phase Equilibrium in the Ternary Systems (Li2B4O7 + MgB4O7 + H2O) and (Na2B4O7 + MgB4O7 + H2O) at 298.15 K Shiqiang Wang,*,†,‡,§ Xuemin Du,† Yan Jing,† Yafei Guo,‡,§ and Tianlong Deng†,‡,§ †
College of Marine and Environmental Sciences, and ‡College of Chemical Engineering and Materials Science, Tianjin University of Science and Technology, Tianjin 300457, P. R. China § Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin 300457, P. R. China ABSTRACT: Solid−liquid phase equilibria of the two ternary systems (Li2B4O7 + MgB4O7 + H2O) and (Na2B4O7 + MgB4O7 + H2O) at T = 298.15 K and p = 0.1 MPa were studied with the isothermal dissolution equilibrium method. Solubilities, densities, pH values, and refractive indices were measured experimentally. In the ternary system (Li2B4O7 + MgB4O7 + H2O) at 298.15 K, there are one invariant point corresponding to (Li2B4O7·3H2O + MgB4O7·9H2O), two isothermal dissolution curves, and two crystallization regions. The crystallized area of MgB4O7·9H2O is increased obviously with the increase of temperature, while that of Li2B4O7·3H2O is decreased slightly. In the ternary system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K, there are one invariant point (Na2B4O7·10H2O + MgB4O7·9H2O), two isothermal dissolution curves, and two crystallization regions. The crystallized area of MgB4O7·9H2O is increased with the increase of temperature, while that of Na2B4O7·10H2O is decreased obviously. Both of the systems belong to a simple eutectic type, and neither double salts nor solid solutions formed.
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forming simple borate crystallization fields.4,5 Hungchaoite (MgB4O7·9H2O), an incongruently dissolved solid, represents a metastable phase, which can exist for quite a long time. Hungchaoite can convert to other magnesium borates, and changes regularly with the impact of density, pH, and common ions effect.6 To understand the thermodynamic behaviors of lithium and borate containing brine, our research group researched some systems at a temperature range from 273.15 to 348.15 K, such as the ternary system (Li+, Mg2+//borate-H2O) at 273.15 and 323.15 K,7,8 (Na2B4O7 + MgB4O7 + H2O)9 and (LiBO2 + CaB2O4 + H2O)10 at 288.15 K, the quaternary system (Li+, Na+//Cl−, SO42‑‑-H2O) at 273.15 K,11 the quinary system (Na+, Mg2+, K+//SO42−, B4O72−-H2O) at 288.15 K12 and (Li+, K+, Rb+, Mg2+//B4O72−-H2O) at 348.15 K.13 To better separate and purify the lithium and borate resource from salt-lake brine, the isothermal solubilities and the corresponding solution physicochemical properties including density, refractive index, and pH value for the two ternary systems (Li2B4O7 + MgB4O7 + H2O) and (Na2B4O7 + MgB4O7 + H2O) at T = 298.15 K and p = 0.1 MPa were presented in this paper.
INTRODUCTION Boron and lithium play important roles in many industries. Boron compounds are used extensively in the pigment, papermaking, medicine, and textile industries, etc. Advanced rechargeable lithium batteries with high voltage and energy density as power sources of many portable instruments and electric vehicles are currently attracting great interest because of the environmental and resource benefits. With the cost decreased and a simple chemical process, the brine has replaced mineral and became the main raw material to produce lithium and boron salts. There are more than 700 salt lakes located in the Qinghai−Tibet Plateau abundant with lithium and boron resources. The main components of its brines can be described with the Li+ + Na+ + K+ + Ca2+ + Cl− + SO42− + borate + H2O system.1 It is well-known that solid−liquid phase equilibrium plays an important role in exploiting salt lake brine resources and describing the geochemical evolution of brine minerals. To exploit the valuable brine resources economically, the phase equilibria and phase diagrams of brine systems containing lithium and boron at different temperatures are required.2,3 Borate in aqueous solution can exist in several different species, such as monoborate [B(OH)4−], diborate [B2O(OH)62−], triborate [B3O3(OH)5−], and polytetraborate [B4O5(OH)42−, B5O6(OH)4−, B6O7(OH)62−], and the dissolving behavior of boron is very complicated. The research of phase equilibria systems containing borate showed that it mainly existed in the form of [B4O5(OH)4]2− and with difficulty formed a solid solution and double salt with other anions and cations, only © 2016 American Chemical Society
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EXPERIMENTAL SECTION Materials. The reagents used were analytical grade and are listed in Table 1. Doubly deionied water (κ < 1 × 10−4 S·m−1,
Received: July 12, 2016 Accepted: November 22, 2016 Published: December 13, 2016 253
DOI: 10.1021/acs.jced.6b00626 J. Chem. Eng. Data 2017, 62, 253−258
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Table 1. Chemical Samples Used in This Study chemical name
source
initial mass fraction purity
purification method
final mass fraction purity
analysis method
Na2B4O7·10H2O Li2B4O7·3H2O MgB4O7·9H2O
Sinopharm Chemical Reagent Co. Ltd. synthesis synthesis
0.99 0.99
recrystallization recrystallization chemical reaction
0.992 0.992 0.99
titration titration titration
of less than ±0.15 mg·cm−3, and pH value was determined by a high precision pH meter (PHSJ-5, Shanghai Precision Scientific Instruments Co. Ltd., China) with an uncertainty of ±0.01. The pH meter was calibrated with standard buffer solutions of a mixed phosphate of potassium dihydrogen phosphate and sodium dihydrogen phosphate (pH 6.84) as well as borax (pH 9.18). The powder X-ray diffractometer (XD-3, Beijing Purk. Instrument Co. Ltd., China). Experimental Method. The equilibrium experiment in this work was conducted by the method of isothermal dissolution equilibrium.15,16 A series of duplicate artificial synthesized complexes were prepared by adding the second salt gradually to the binary saturated point at 298.15 K. The solid and solution were all put into the sealed hard glass bottles which were placed in magnetic stirring thermostatic water baths at 298.15 ± 0.1 K with continuous stirring in order to accelerate the establishment of equilibrium states. At regular intervals, the magnetic stirring was paused for 4 h to take the supernatant out for chemical analysis, and when the composition of the supernatant became constant, it indicated that the equilibrium had been achieved. It took about 10 days to reach equilibrium. And then, the corresponding solution physicochemical properties including ρ, pH, and nD were determined, samples of the liquid phase and solid phase were taken for chemical analysis. The solid phases were identified combined with Schreinemakers’ method and the X-ray diffractometer. Analytical Methods. The borate ion concentration (B4O72−) was evaluated by alkali titration method of mannitol with sodium hydroxide standard solution in the presence of a double indicator of methyl red and phenolphthalein (precision: ±0.3%). The magnesium ion concentration (Mg2+) was evaluated by a complexometric titration with EDTA (precision: ±0.3%). The significant interference of the Li+ ion was eliminated by adding anhydrous alcohol and n-butanol as a masking agent.17 The lithium ion (Li+) was measured by an inductively coupled plasma optical emission spectrometer (ICP-OES, Prodigy, Leman Corporation, America. Precision: ±1.0%). The Na+ concentration was evaluated using an ion balance combined with analytical verification using ICP-OES.
Figure 1. X-ray diffraction pattern of hungchaoite (MgB4O7·9H2O).
Table 2. Solubility, Density, Refrative Index of the System Li2B4O7 + H2O at T = 298.15 K and p = 0.1 MPaa system Li2B4O7 + H2O
solubility in water 100wb ρ/(g·cm−3) 2.88 2.94 2.96 2.843 2.88
1.0229 −c 1.0256 1.0256 1.02342
nD
ref
1.3391 −c 1.3380 1.3381 1.3394
18 19 20 21 this work
a
Standard uncertainties u are u(T) = 0.02 K, u(p) = 0.005 MPa. bw = mass fraction. cNot detected.
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RESULTS AND DISCUSSION The solubility, density, and refractive index for the binary system Li2B4O7 + H2O at 298.15 K have been reported. A comparison between experimental data of Li2B4O7 in water and the values from literature are presented in Table 2 and Figure 2. It was observed that the solubility of Li2B4O7 increases with increasing temperature. It is clear from Table 2 and Figure 2 that the experimental results show good agreement with the literature data, and this agreement indicates our experimental procedure and analysis are reliable. Phase Diagram of the System (Li2B4O7 + MgB4O7 + H2O) at 298.15 K. The solubilities, densities, refractive indices, and pH values of the ternary system (Li2B4O7 + MgB4O7 + H2O) at 298.15 K were listed in Table 3. The composition of the liquid phase in the aqueous ternary system was expressed in mass fraction (wb). According to the solubility data in Table 3, the
Figure 2. Comparison of the experimental solubilities of Li2B4O7 with literature data: ○, ref 22; ◆, this work.
pH 6.60) was employed to prepare the series of the artificially synthesized and chemical analysis. The hungchaoite was synthesized in the lab,14 and identified by chemical composition analysis and X-ray powder diffraction, the results of which are shown in Figure 1. Apparatus. A thermostat with magnetic stirring (XHC-5006, Beijing Fortunejoy Sci. Technol. Co. Ltd.) was used to control the temperature with a precision of 0.01 K for the equilibrium experiment. Refractive index (nD) was measured by an Abbe refractometer (WAY-2S, Shanghai Yuguang Instrument Co. Ltd., China) with an uncertainty within ±0.0001. Density (ρ) was measured using an Anton Paar Digital vibrating-tube densimeter (DMA 4500, Anton Paar Co. Ltd., Austria) with an uncertainty 254
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Table 3. Solubilities and Physiochemical Properties of the System (Li2B4O7 + MgB4O7 + H2O) at T = 298.15 K and p = 0.1 MPaa composition of liquid phase 100wb
composition of wet residue 100w
ρ
no.
Li2B4O7
MgB4O7
Li2B4O7
MgB4O7
g·cm−3
nD
pH
solid phase
1,A 2 3 4 5 6 7,E 8 9 10,B
0.00 0.45 0.70 1.31 1.72 2.04 2.91 2.90 2.88 2.88
0.64 0.34 0.23 0.15 0.13 0.13 0.13 0.11 0.06 0.00
0.00 0.29 0.55 0.97 1.26 1.61 7.35 9.43 5.75 6.07
14.76 15.74 13.69 14.50 13.93 12.28 8.41 0.05 0.04 0.00
1.00277 1.00225 1.00437 1.01027 1.01334 1.01608 1.02499 1.02461 1.02389 1.02342
1.3345 1.3351 1.3355 1.3366 1.3372 1.3380 1.3395 1.3395 1.3397 1.3394
9.14 9.22 9.26 9.33 9.39 9.42 9.54 9.52 9.46 9.47
MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O + Li2B4O7·3H2O Li2B4O7·3H2O Li2B4O7·3H2O Li2B4O7·3H2O
Standard uncertainties u are u(T) = 0.02 K, u(p) = 0.005 MPa, u(ρ) = 0.15 mg·cm−3, u(nD) = 0.0001, u(pH) = 0.01 pH, ur(Li2B4O7) = 0.003, ur(MgB4O7) = 0.003. bw = mass fraction. a
Figure 4. X-ray diffraction pattern of solid phases in the system (Li2B4O7 + MgB4O7 + H2O) at 298.15 K.
Figure 3. Phase diagram of the system (Li2B4O7 + MgB4O7 + H2O) at 298.15 K. ●, liquid phase; , isothermal curve; ▲, wet solid phase; ···, Schreinemakers lines.
phase diagram of the system was shown in Figure 2, respectively. In Figure 3a, there are one invariant point corresponding to E (MgB4O7·9H2O + Li2B4O7·3H2O) which liquid compositions are w(Li2B4O7) = 2.91%, w(MgB4O7) = 0.13%, two univariant solubility curves of AE and BE; two crystallization regions corresponding to MgB4O7·9H2O and Li2B4O7·3H2O, and the crystallization regions of MgB4O7·9H2O is much larger than Li2B4O7·3H2O due to the differences of the solubility of two salts in themselves. The ternary system is a simple eutectic type, and neither double salt nor solid solution was found. To identify the solid phases, the composition of wet residue is shown in Figure 3b, and the corresponding X-ray powder diffraction is drawn in Figure 4. It shows that salts MgB4O7·9H2O and Li2B4O7·3H2O coexist at the invariant point E.
Figure 5. Comparison of the phase diagram of the system (Li2B4O7 + MgB4O7 + H2O) at 273.15, 298.15, and 323.15 K.···■···, ref 7; −●−, this work; ···▼···, ref 15. 255
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Figure 7. Phase diagram of the system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K. ●, liquid phase; , isothermal curve; ▲, wet solid phase; ···, Schreinemakers lines.
(this study) is shown in Figure 5. It was found that (1) the solid phase numbers and the existing minerals at different temperatures are similar; (2) the solubility curves of B1E1 and B2E2 changed regularly with the increasing concentration of MgB4O7 at 273.15 and 323.15 K, while that of curve BE at 298.15 K did not change; (3) the area of crystallization region of Li2B4O7· 3H2O decreases obviously as the temperature increases from 273.15 to 373.15 K while that of MgB4O7·9H2O increases obviously with the increasing temperature.
Figure 6. Physicochemical properties versus composition diagram of the system (Li2B4O7 + MgB4O7 + H2O) at 298.15 K.
The comparison of the solubility data of the ternary system Li2B4O7 + MgB4O7 + H2O at 273.15 K,7 323.15 K15 and 298.15 K
Table 4. Solubilities and Physiochemical Properties of the System (Na2B4O7 + MgB4O7 + H2O) at T = 298.15 K and p = 0.1 MPaa composition of liquid phase 100wb
composition of wet residue 100w
ρ
no.
Na2B4O7
MgB4O7
Na2B4O7
MgB4O7
g·cm−3
nD
pH
solid phase
1,C 2 3 4 5 6 7 8 9,F 10 11 12 13 14,D
0.00 0.40 0.80 1.16 1.41 2.06 2.27 3.01 3.11 3.10 3.09 3.08 3.08 3.08
0.64 0.41 0.27 0.19 0.18 0.15 0.14 0.14 0.14 0.14 0.13 0.06 0.03 0.00
0.00 0.30 0.63 0.86 0.96 1.43 1.86 2.24 7.73 c 42.90 39.27 29.22
14.76 14.07 10.29 13.30 17.39 15.55 10.55 13.52 1.24 c 0.04 0.03 0.01
1.00277 1.00528 1.00671 1.01055 1.01169 1.01794 1.01936 1.02693 1.02699 1.02677 1.02636 1.02616 1.02610 1.02565
1.3345 1.3352 1.3360 1.3367 1.3370 1.3378 1.3380 1.3394 1.3397 1.3397 1.3394 1.3393 1.3390 1.3390
9.14 9.23 9.28 9.34 9.35 9.41 9.45 9.62 9.68 9.68 9.66 9.65 9.61 9.55
MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O MgB4O7·9H2O+Na2B4O7·10H2O Na2B4O7·10H2O Na2B4O7·10H2O Na2B4O7·10H2O Na2B4O7·10H2O Na2B4O7·10H2O
Standard uncertainties u are u(T) = 0.02 K, u(p) = 0.005 MPa, u(ρ) = 0.15 mg·cm−3, u(nD) = 0.0001, u(pH) = 0.001 pH, ur(Na2B4O7) = 0.003, ur(MgB4O7) = 0.003. bw = mass fraction. cNot detected. a
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Figure 9. Comparison of phase diagram of the system (Na2B4O7 + MgB4O7 + H2O) at 288.15 and 298.15 K. −●−, this work; ···▼···, ref 9.
are the same, while the area of crystallization region of Na2B4O7· 10H2O decreased as temperature increases, while that of MgB4O7· 9H2O increased obviously with the increasing temperature. Solution Physicochemical Properties of the System (Na2B4O7 + MgB4O7 + H2O) at 298.15 K. On the basis of the values in Table 4, the physicochemical properties including
Figure 8. X-ray diffraction pattern of solid phases in the system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K.
Solution Physicochemical Properties of the System (Li2B4O7 + MgB4O7 + H2O) at 298.15 K. According to the experimental data of Table 3, the physicochemical properties containing density, refractive index, and pH value versus composition diagrams of the ternary system at 298.15 K were plotted in Figure 6. It can be seen that the solution physicochemical properties changed regularly with the increase of Li2B4O7 concentration. In Figure 6a, the solution density increased gradually and reached the maximum value of 1.02499 g·cm−3 at the invariant point. Figure 6 panels b and c showed the variation trend of refractive index value and pH with the Li2B4O7 concentration, and reached the maximum values 1.3395 and 9.54 at the invariant point, respectively. Phase Diagram of the System (Na2B4O7 + MgB4O7 + H2O) at 298.15 K. The solubility data and physiochemical properties of ternary system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K are presented in Table 4. On the basis of the experiment results, the phase diagram of this system is drawn in Figure 7. In Figure 7a, there are one invariant point F (MgB4O7·9H2O + Na2B4O7·10H2O) which denotes the compositions of Na2B4O7 and MgB4O7 in the liquid phase: w(Na2B4O7) = 3.11%, w(MgB4O7) = 0.14%, respectively, two univariant solubility curves of CF and DF, and two crystallization regions corresponding to MgB4O7·9H2O and Na2B4O7·10H2O. Owing to the differences of the solubility of two salts in themselves and the salting-out effect of Na2B4O7 to MgB4O7, the crystallization regions of MgB4O7·9H2O is much larger than Na2B4O7·10H2O. The equilibrium solid phase was identified using wet residue (Figure 7b) and powder X-ray diffraction (Figure 8). The phase diagram of the ternary system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K in our study compares with that at 288.15 K9 and is shown in Figure 9. It was found that the solid phase numbers
Figure 10. Physicochemical properties versus composition diagram of the system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K. 257
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(5) Gao, S. Y.; Xia, S. P. Advancement in Chemistry of Borate in Salt Lake brines. Chin. Sci. Bull. 1999, 12, 12−16. (6) Sun, B.; Song, P. S. Study on Solution and Phase Transformation of some Magnesium Borates. J. Salt Lake Res. 1999, 7, 16−22. (7) Fu, C.; Sang, S. H.; Zhou, M. F.; Liu, Q. Z.; Zhang, T. T. Phase Equilibria in the Ternary Systems Li2B4O7-MgB4O7-H2O and K2B4O7MgB4O7-H2O at 273 K. J. Chem. Eng. Data 2016, 61, 1071−1077. (8) Li, M. L.; Duo, J.; Yu, X. D. Stable Phase Equilibrium in the Aqueous Ternary System Li+, Mg2+//borate-H2O at 323 K. J. Salt Chem. Ind. 2014, 10, 16−19. (9) Peng, J. Study on Equilibria in the quinary system Na+, Mg2+, K+// SO42‑, B4O72‑-H2O at 288 K. Master Thesis, Chengdu University of Technology, Chengdu, 2008. (10) Wang, S. Q.; Guo, Y. F.; Liu, W. J.; Deng, T. L. Phase equilibria in the aqueous ternary system (LiBO2+CaB2O4+H2O) at 288.15 and 298.15K. J. Solution Chem. 2015, 44, 1545−1554. (11) Wang, S. Q.; Deng, T. L. Metastable phase equilibrium in the aqueous quaternary system containing lithium, sodium, chloride, and sulfate at 273.15 K. J. Chem. Eng. Data 2010, 55, 4211−4215. (12) Sang, S. H.; Peng, J. (Solid + liquid) equilibria in the quinary system Na+, Mg2+, K+//SO42‑, B4O72‑-H2O at 288 K. CALPHAD: Comput. Coupling Phase Diagrams Thermochem. 2010, 34, 64−67. (13) Yu, X. D.; Zeng, Y.; Guo, S. S.; Zhang, Y. J. Stable Phase Equilibrium and Phase Diagram of the Quinary System Li+, K+, Rb+, Mg2+//Borate-H2O at T = 348.15 K. J. Chem. Eng. Data 2016, 61, 1246−1253. (14) Jing, Y. A new method of synthesis of Hungchaoite. J. Sea-Lake Salt Chem. Ind. 1999, 2, 24−25. (15) Wang, S. Q.; Guo, Y. F.; Li, D. C.; Zhao, F. M.; Deng, T. L.; Qiao, W. Solid-Liquid Phase Equilibria in the Ternary Systems (LiCl +MgCl2+H2O) and (Li2SO4+MgSO4+H2O) at 288.15 K. J. Chem. Eng. Data 2015, 60, 821−827. (16) Wang, S. Q.; Guo, Y. F.; Li, D. C.; Tang, P.; Deng, T. L. Experimental determination and modeling of the solubility phase diagram of the ternary system (Li2SO4+K2SO4+H2O) at 288.15 K. Thermochim. Acta 2015, 601, 75−81. (17) Gao, J.; Guo, Y. F.; Wang, S. Q.; Deng, T. L.; Chen, Y. W.; Belzile, N. Interference of lithium in measuring in measuring magnesium by complexometry: Discussions of the mechanism. J. Chem. 2013, 2013, 1− 4. (18) Song, P. S.; Du, X. H.; Xu, H. C. The phase equilibrium and properties of the saturated solution in the ternary system Li2B4O7Li2SO4-H2O at 25°C. Chin. Sci. Bull. 1984, 29, 1072−1076. (19) Lepeshkov, I. N.; Bodaleva, N. V.; Kotova, L. T. The solubilities of the ternary system (LiCl + Li2B4O7 + H2O) and (Li2B4O7 + K2B4O7 + H2O) at 25°C. Rus. J. Inorg. Chem. 1963, 8, 2599−2608. (20) Sang, S. H.; Deng, T. L.; Tang, M. L.; Yin, H. A. An experimental study of solubilities and properties of solution in the system (Li2B4O7 Na2B4O7 - H2O) at 25°C. J. Chengdou Univ. Technol. 1997, 24, 87−92. (21) Zeng, Y.; Yin, H. A.; Tang, M. L.; Deng, T. L. An experimental study of solubilities and properties of solution in the system (Li2B4O7 Na2B4O7 - H2O) at 25°C. Chin. J. Chem. Eng. Univ. 2000, 14, 77−80. (22) Reburn, W. T.; Gale, W. A. The System Lithium Oxide−Boric Oxide−Water. J. Phys. Chem. 1955, 59, 19−24.
density, pH value, and refractive index versus composition diagrams for the ternary system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K were plotted in Figure 10. It shows that the density, refractive index, and pH in the ternary system increased regularly with the increasing concentration of Na2B4O7 in the solution, and the maximum value occurred at the invariant point F where ρ = 1.02699 g·cm−3, nD = 1.3397, and pH = 9.68.
5. CONCLUSION Solubilities, densities, refractive indices, and pH values of two ternary systems (Li2B4O7 + MgB4O7 + H2O) and (Na2B4O7 + MgB4O7 + H2O) at T = 298.15 K and p = 0.1 MPa was investigated with the method of isothermal dissolution equilibrium. (1) In the system (Li2B4O7 + MgB4O7 + H2O) at 298.15 K, there are one invariant point corresponding to (Li2B4O7· 3H2O + MgB4O7·9H2O), two isothermal dissolution curves, and two crystallization regions. An examination of the phase diagram for the ternary system at (273.15 K, 298.15 K and 323.15) K shows that the area of crystallization region of MgB4O7·9H2O is increased obviously with the increasing of temperature, while that of Li2B4O7·3H2O is decreased slightly. (2) In the system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K, there are one invariant point (Na2B4O7·10H2O + MgB4O7· 9H2O), two isothermal dissolution curves, and two crystallization regions. When the experimental phase diagram at 298.15 K is compared with that at 288.15 K, it shows that the area of crystallization region of MgB4O7· 9H2O is increased with increasing temperature, while that of Na2B4O7·10H2O is decreased obviously. Both systems belong to a simple eutectic type, and neither double salts nor solid solutions formed. (3) The solution density, refractive index, and pH value in the two ternary systems at 298.15 K change regularly, and reach the maximum values at the invariant point.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Tel.: +86-22-60601156. ORCID
Shiqiang Wang: 0000-0002-6733-7076 Tianlong Deng: 0000-0002-1728-2943 Funding
This work was supported by financial contributions from the National Natural Science Foundation of China (U1507109, U1407113, 21306136, 21276194, and 21106103), the Training Program for Changjiang Scholars and Innovative Research Team in University ([2013]373), and the Innovative Research Team of Tianjin Municipal Education Commission (TD12-5004). Notes
The authors declare no competing financial interest.
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REFERENCES
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