273 K下Na2CO3-Na2SO4-Na2B4O7-H2O四元体系介稳相平衡的实验研究

采用等温蒸发法研究了四元体系Na2CO3-Na2SO4-Na2B4O7-H2O在273 K时的介稳相平衡及平衡液相的密度. 利用溶解度数据绘制了该四元体系273 K下的相图. 研究结果表明, 该四元体系有异成分复盐2Na2SO4·Na2CO3形成. 相图中有2个共饱点、5条单变量曲线和4个结晶相区. 4个结晶相区分别为盐Na2CO3·10H2O, Na2SO4·10H2O, Na2B4O7·10H2O和2Na2SO4·Na2CO3的结晶区. 复盐2Na2SO4·Na2CO3同时存在于包含Na2CO3-Na2SO4-H2O三元体系的其它四元体系或高元体系中. 在273 K介稳平衡相图中, 碳酸钠以Na2CO3·10H2O形式析出; 硫酸钠以Na2SO4·10H2O的形式析出; 硼酸钠的完整分子式为Na2B4O5(OH)4·8H2O. Na2CO3对Na2B4O7有盐析作用.     

K2B4O7-Na2B4O7-Li2B4O7-H2O四元体系273 K介稳相平衡

采用等温蒸发平衡法研究了四元体系K2B4O7-Na2B4O7-Li2B4O7-H2O在273 K时的介稳相平衡及平衡液相的密度. 研究发现该四元体系为简单共饱和型, 无复盐及固溶体形成, 根据溶解度数据绘制了相图, 相图中有一个共饱点E, 三条单变度曲线E3E, E2E, E1E; 三个平衡固相分别为K2B4O7·4H2O、Na2B4O7·10H2O 和LiBO2·8H2O. 并简要讨论了实验结果.     

Na+, K+//Cl-, B4O2-7-H2O四元体系273 K介稳相平衡

采用等温蒸发法研究了四元体系Na+, K+//Cl-, B4O2-7-H2O 273 K时的介稳相平衡与相图. 测定了该体系273 K平衡液相中各组分的溶解度及平衡液相的密度; 绘制了该体系的介稳相图. 该四元体系273 K相图由5条溶解度单变量线、4个结晶区及2个共饱和点组成. 体系无复盐或固溶体形成. 四个结晶区分别对应单盐NaCl、KCl、K2B4O7·4H2O 和Na2B4O7·10H2O. 共饱点E1处KCl、NaCl及Na2B4O7·10H2O三盐共饱和,所对应的平衡液相组成为w(Cl-)=29.15%, w(B4O2-7)=0.64%, w(K+)=5.97%, w(Na+)=15.55%; 共饱和点E2处盐KCl、Na2B4O7·10H2O和K2B4O7·4H2O的三盐共饱和, 所对应的平衡液相组成为w(Cl-)=22.84%, w(B4O2-7)=10.98%, w(K+)=28.01%, w(Na+)=1.53%. 同体系298 K时的稳定相图相比, 273 K时硼酸钠的结晶区变大, 而硼酸钾、氯化钠结晶区变小.     

Mg2+, K+//Cl-, B4O2-7-H2O四元体系288 K固液相平衡

采用等温溶解平衡法研究了288 K时Mg2+, K+//Cl-, B4O2-7-H2O四元体系的相平衡关系, 测定该体系在288 K时平衡液相的溶解度和密度. 依据实验测定的平衡溶解度数据及对应的平衡固相, 绘制了该四元体系的平衡相图以及其密度-组成图. 研究结果表明, 四元体系Mg2+, K+//Cl-, B4O2-7-H2O 288 K时的固液相平衡实验中, 有复盐KCl·MgCl2·6H2O生成, 平衡相图中有3个共饱点, 7条单变量曲线, 5个结晶区, 对应的平衡固相分别为MgB4O7·9H2O, K2B4O7·4H2O, KCl, MgCl2·6H2O, KCl·MgCl2·6H2O. 简要讨论了实验结果.     

Solid-liquid Equilibria in the Quaternary System Na＋, K＋//Br-, B4O72--H2O at 298 K

According to the compositions of the underground gasfield brines in the west of Sichuan Basin, the solu- bilities and densities of the solid-liquid equilibria in the quaternary system Na＋, K＋//Br-, B4O72--H2O at 298 K were determined by the method of isothermal solution saturation. From the experimental data, the phase diagram, water content diagram and density-composition diagram were obtained. This quaternary system is of simple eutectic type, without double salt and solid solution. There are two invariant points, five univariant curves, four fields of crystalli- zation in the system. The equilibrium solid phases are Na2BaO7·10H20, K2B4O7·4H2O, NaBr·2H2O and KBr. Na2B4O7·10H2O has a larger crystallization field, and NaBr·2H2O has a smaller crystallization field. It is also found that bromide has the salting-out effect on borate in the quaternary system Na＋, K＋//Br-, B4O72--H2Oat 298 K.     

(Solid+Liquid) Equilibria in the Quaternary System Na2B4O7-MgB4O7-K2B4O7-H2O at 288 K

(Solid+Liquid) phase equilibria in the quaternary system Na₂B₄O₇‐MgB₄O₇‐K₂B₄O₇‐H₂O at 288 K were studied experimentally using the method of isothermal solution saturation. Solubility of any single salt in the solution of the quaternary system was determined experimentally. Based on the experimental data achieved, the phase diagram and water content diagram of the quaternary system were constructed, respectively. In the phase equilibrium diagram of the quaternary system Na₂B₄O₇‐MgB₄O₇‐K₂B₄O₇‐H₂O at 288 K, there are one invariant point E, three univariant curves E1E, E2E and E3E, and three fields of crystallization corresponding to Na₂B₄O₇·10H₂O, K₂B₄O₇·4H₂O and MgB₄O₇·9H₂O. The experimental results show that potassium borate (K₂B₄O₇·4H₂O) have higher solubilities than the magnesium borate and sodium borate in the quaternary system Na₂B₄O₇‐MgB₄O₇‐K₂B₄O₇‐H₂O at 288 K.     

Li＋,Na＋∥,CO32－,B4O72－-H2O 四元交互体系288 K的相平衡

采用等温溶解平衡法对Li＋,Na＋∥,CO32－,B4O72－-H2O四元体系进行288 K相平衡研究.结果表明,该体系属简单共饱型，在288 K等温溶解度相图中有二个共饱点，五条单变量曲线，平衡固相为Na2CO3•10H2O， Li2B4O7•3H2O，Na2B4O7•10H2O, Li2CO3.     

四元交互体系Li+，K+/CL-，CO2-3-H2O在298 K时相平衡及物理化学性质研究

Zabuye Saline Lake, Tibet, China, is unrivalled in the world for its very high salinity, in particular, for the very high concentration of ions of lithium, potassium, and boron in the brine. It belongs to alkaline and carbonate-borate-type salt lake. As a part of the study on phase equilibrium of the 6component subsystem Li+, Na+, K+/C1-, CO2-3, B4O2-7-H2O of the brine system, a study on the reciprocal quaternary system Li+, K+/C1-, CO32-H2O at 298 K was done with isothermal dissolution equilibrium method in the present work. The phase equilibrium of the reciprocal quaternary system Li+,K+/C1, CO2-3-H2O at 298 K was studied with isothermal dissolution method in this work. The physicochemistry properties of the corresponding equilibrium solutions such as densities, viscosities, refractive index, conductivities and pH value were determined. The dried salt diagram of the system consists of four crystallization fields (KC1, Li2CO3, LiCI·H2O, K2CO3·3/2H2O) and five isothermal solubility curves.There are no double slat or solid solution found. Pitzer′s model of the electrolyte solution theory was used for parameterization from the results of solubility determination for subsystems and the prediction of solubilities for the reciprocal quaternary system was made. The solubility data of the experiment are in agreement with those calculated.     

Metastable Phase Equilibrium in the Reciprocal Quaternary System LiCl+MgCl2+Li2SO4+MgSO4+H2O at 348.15 K and 0.1 MPa

The metastable solubilities and the physicochemical properties including density and pH of the reciprocal quaternary system(LiCl+MgCl₂+Li₂SO₄+MgSO₄+H₂O) at 348.15 K and 0.1 MPa were determined using the isothermal evaporation method. The dry-salt diagram and water-phase diagram were plotted based on the experimental data. There are five invariant points, eleven univariant curves, and seven crystallization zones corresponding to hexahydrite, tetrahydrite, kieserite, bischofite, lithium sulfate monohydrate, lithium chloride monohydrate and lithium carnallite. Comparison between the stable and metastable diagrams at 348.15 K indicates that the metastable phenomenon of magnesium sulfate is obvious, and the crystallization regions of hexahydrite and tetrahydrite disappear in the stable phase diagram. A comparison of the metastable dry-salt phase diagrams at 308.15, 323.15 and 348.15 K shows that with the increasing of temperature the epsomite crystallization zone disappears from the dry-salt phase diagram of 303.15 K, and a new kieserite crystallization zone is presented at 348.15 K. The density and pH in the metastable equilibrium solution present regular change with the increasing of Jänecke index J(2Li⁺), and the calculated densities using the empirical equation agree well with the experimental values.     

Measured and Predicted Solubility Phase Diagrams of Quaternary Systems LiBr-NaBr-MgBr2-H2O and LiBr-KBr-MgBr2-H2O at 298.15 K

The stable phase equilibria of quaternary systems LiBr-NaBr-MgBr₂-H₂O and LiBr-KBr-MgBr₂-H₂O at 298.15 K were studied by both experimental measurement(isothermal solution saturation method) and theoretical prediction(Pitzer model). The solubilities of the saturated solution have been determined experimentally and two stable phase diagrams and relevant water diagrams of the two quaternary systems were obtained. Results show that quaternary system LiBr-NaBr-MgBr₂-H₂O is hydrate II type as NaBr and NaBr·2H₂O coexistence. Its phase diagram consists of only one invariant point, four univariant curves, and five crystallization fields. The quaternary system LiBr-KBr-MgBr₂-H₂O is a complex type as the double salt KBr·MgBr₂·6H₂O formed. In addition to this double salt, the three single salts LiBr·2H₂O, KBr and MgBr₂·6H₂O also crystallize. In this paper, the solubilities of phase equilibria in above quaternary systems were also calculated by the Pitzer's electrolyte solution model. All the needed parameters can be obtained from the literature or be fitted by experimental data. On the Basis of the experimental and calculated results, the phase diagram of the quaternary system was plotted for comparison. It shows that the calculation results are consistent with the experimental ones.     

K2B4O7-Na2B4O7-Li2B4O7-H2O 四元体系15℃介稳相平衡研究

采用等温蒸发平衡法研究了四元体系K2B4O7-Na2B4O7-Li2B4O7-H2O15℃时的介稳相平衡及平衡液相的物化性质(密度,粘度,电导率,折光率,pH)。根据实验数据绘制了相图,相图中有一个共饱点E,三条单变度曲线E3F,E2F,E1F;三个平衡固相分别为：K2B4O7•4H2O,Na2B4O7•10H2O和Li2B2O4•16H2O;硼酸钾具有最大溶解度,硼酸钠具有最小溶解度。同时,根据试验数据绘制了组成－物化性质关系图,从图可见溶液的密度,粘度和折光率均随着溶液浓度的增大而逐渐增大,在共饱和点F处达到最大值,而溶液的pH值和电导率却随着溶液浓度的增大呈总体下降的趋势。     

Isothermal Evaporation of Quaternary System Li^＋, K^＋, Mg^2＋//Cl^--H2O at 348K

The solubilities of the quaternary system Li^＋,K^＋,Mg2^＋//Cl^--H2O were investigated at 348 K via isothermal evaporation.The densities and refractive indices of its equilibrated solution were also determined experimentally.On the basis of the obtained data,the metastable phase diagram,the water content diagram,the diagrams of the density and refractive index against the composition of this quaternary system were constructed.The quaternary system Li^＋,K^＋,Mg^2＋//Cl^--H2O at 348 K belongs to a complex type with the formation of two carnallite double salts,which are potassium carnallite（K-carnallite） and lithium carnallite（Li-carnallite）.There are five salts like potassium chloride （KCl）,lithium chloride monohydrate（LiCl.H2O）,bischofite（MgCl2·6H2O）,K-carnallite（KCl·MgCl2·6H2O） and Li-carnallite（LiCl·MgCl2·7H2O）,seven unvariant curves named AH3,BH2,CH3,DH1,EH1,H1H2 and H2H3,and three invariant points,namely H1,H2 and H3,included in this metastable phase diagram.Comparisons between the stable phase diagram at 298 K and metastable phase diagram at 348 K of this quaternary system show that all the crystalline forms of the salts are not changed,whereas the crystallization areas of salts are changed significantly with temperature.The scope of KCl crystallization increases from 82% to 95% and that of K-carnallite decreases from 15.80% to 0.32% along with the temperature increasing from 298 K to 348 K,respectively.     

Solid-liquid Equilibria in the Ternary System (NaCl+SrCl2+H2O) and (KCl+SrCl2+H2O) at 288.15 K and 0.1 Mpa

Solid-liquid phase equilibria of the two ternary systems (NaCl+SrCl₂+H₂O) and (KCl+SrCl₂+H₂O) at T=288.15 K and p=0.1 MPa were studied using the isothermal dissolution equilibrium method. Solubilities of the equilibrium liquid phase were determined, and the solids were also investigated by the Schreinemaker method of wet residues. In the ternary system (NaCl+SrCl₂+H₂O) at 288.15 K, there is one invariant point corresponding to (NaCl+SrCl₂·6H₂O) and two crystallization regions corresponding to NaCl and SrCl₂·6H₂O. The crystallized area of SrCl₂·6H₂O decreased with the increasing temperature, while that of NaCl increased slightly. In the ternary system (KCl+SrCl₂+H₂O) at 288.15 K, there is one invariant point(KCl+SrCl₂·6H₂O) and two crystallization regions corresponding to KCl and SrCl₂·6H₂O. Both systems belong to a simple eutectic type, and neither double salts nor solid solutions were formed. On the basis of Pitzer-Harvie-Weare model, the solubilities of the two systems at 288.15 K were demonstrated. A comparison showed that the calculated solubilities agreed well with the experimental data.     

三元体系Li+, K+(Mg2+)/SO2-4-H2O 25 ℃相关系和溶液性质的研究

研究了两个三元体系Li~+，K~+/SO_4~(-2)-H_2O(1)和Li~+，Mg~(2+)/SO_4~(2-)-H_2O(2)在25 ℃时的相关系和溶液密度、粘度、折光率、电导、pH等物化性质．体系(1)25 ℃等温图由三条溶解度线构成，分别对应于K_2SO_4、复盐LiKSO_4和Li_2SO_4·H_2O相区．复盐LiKSO_4 25 ℃时为不相称溶解化合物，其转变温度为45.5～46 ℃，高于此温度时变为相称溶解．复盐与LiSO_4无固溶体形成．体系(2)为简单共饱型，两段溶解度线对应于体系的两种原始组分Li_2SO_4·H_2O和MgSO_4·7H_2O的结晶区，无复盐或固溶体形成，亦未发生脱水作用．用Pitzer模型检验测得的两个体系25 ℃的溶解度，并用经验或半经验公式描述物化性质随浓度的变化规律，其结果令人满意．     

Mg2+,K+//Cl-,B4O2-7-H2O四元体系288 K固液相平衡

采用等温溶解平衡法研究了288 K时Mg2+,K+//Cl-,B4O2-7-H2O四元体系的相平衡关系,测定该体系在288 K时平衡液相的溶解度和密度.依据实验测定的平衡溶解度数据及对应的平衡固相,绘制了该四元体系的平衡相图以及其密度-组成图.研究结果表明,四元体系Mg2+,K+//Cl-,B4O2-7-H2O 288 K时的固液相平衡实验中,有复盐KCI·MgCl2·6H2O生成,平衡相图中有3个共饱点,7条单变量曲线,5个结晶区,对应的平衡固相分别为MgB4O7·9H2O,K2B4O7·4H2O,KCl,MgCl2·6H2O,KCl·Mgcl2·6H2O.简要讨论了实验结果.     

Solid-liquid Metastable Equilibria in Quaternary System Li_2SO_4+Li_2CO_3+Li_2B_4O_7+H_2O at 288 K

Metastable equilibrium solubilities and densities of quaternary system Li2SO4+Li2CO3+ Li2B4O7+H2O at 288 K were determined by isothermal evaporation method. According to the experimental data, the metastable equilibrium phase diagram was plotted. The metastable phase diagram had one invariant point F, three double saturated liquid curves E1F, E2F and E3F, and three crystallization fields corresponding to Li2SO4·H2O, Li2CO3 and LiBO2·8H2O. It was found that lithium sulphate(Li2SO4) had the highest concentrat...     

K2CO3-Na2CO3-Li2CO3-H2O四元体系288K的相平衡

水盐体系;碳酸盐;溶解度;盐湖卤水;K2CO3-Na2CO3-Li2CO3-H2O四元体系288K的相平衡     

Li+，Na+//CO32-，B4O72--H2O交互四元体系273 K介稳相平衡研究

我国青藏高原由于特殊的地理气候特点而盐湖众多,西藏境内的扎布耶盐湖卤水中锂、硼、钾浓度之高,在世界盐湖中也非常罕见[1-3].     

Li+,Na+∥CO2-3,B4O2-7-H2O四元交互体系288K的相平衡

采用等温溶解平衡法对Li+,Na+∥CO2-3,B4O2-7-H2O四元体系进行288K相平衡研究.结果表明,该体系属简单共饱型,在288K等温溶解度相图中有二个共饱点,五条单变量曲线,平衡固相为Na2CO3@10H2O,Li2B4O7@3H2O,Na2B4O7@10H2O,Li2CO3.     

Li+，Na+//SO42-，B4O72--H2O交互四元体系288 K介稳相平衡研究

采用等温蒸发法研究了四元体系Li⁺，Na⁺//SO₄^2-，B₄O₇^2--H₂O 288 K介稳相平衡及平衡液相物化性质(密度、电导率、折光率、粘度和pH值)，测定了该四元体系288 K条件下介稳平衡溶液溶解度及物化性质。根据实验数据绘制了相应的介稳相图及物化性质组成图。研究发现：该体系介稳平衡中有复盐Li₂SO₄·Na₂SO₄形成。其介稳相图中有3个共饱和点，7条单变量曲线，平衡固相为：Li₂SO₄·H₂O，Na₂SO₄，Li₂SO₄·Na₂SO₄，Li₂B₄O₇·3H₂O，Na₂B₄O₇·10H₂O。复盐Li₂SO₄·Na₂SO₄和一水硫酸锂(Li₂SO₄·H₂O)有较小的结晶区，而Li₂B₄O₇·3H₂O和Na₂B₄O₇·10H₂O有较大的结晶区；该四元体系介稳平衡条件下未发现Na₂SO₄·10H₂O的结晶区。