Solid-liquid Metastable Equilibria in Quaternary System （NaCl＋Na2CO3＋Na2SO4＋H2O） at 273.15 K

The metastable phase equilibria of the quaternary system NaCl+Na2CO3+Na2SO4+H2O were studied at 273.15 K. The salts' solubilities, densities and pH values of the equilibrated solution in this system were determined. According to the experimental data, the metastable equilibrium phase diagram, the diagram of density vs. composition and pH vs. composition diagram were plotted. The phase diagram consists of five univariant curves, four crystallization fields and two invariant points. The four crystallization fields correspond to sodium carbonate decahydrate (Na2CO3·10H2O), sodium sulfate decahydrate(Na2SO4·10H2O), sodium chloride(NaCl) and burkeite(2Na2SO4· Na2CO3), respectively. The crystallization field of sodium sulfate decahydrate(Na2SO4·10H2O) is the largest, which indicates that sodium sulfate is easy to saturate and crystallize from solution at 273.15 K.     

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.     

四元交互体系Li+,Na+//CO2-3,B4O72一-H2O 298 K相关系的理论预测及实验研究

采用三元体系的溶解度数据,运用多元线性回归法拟合了Li 2CO3(a),Na 2CO3(b),Li 2B4O7(c)的单盐参数、溶解平衡常数及有关的混合离子作用参数.它们的值分别为:β(o)a=-1.235 5,β(1)a=-2.654 6,Cφa=-0.004 660 7,β(0)b=-3.030 6,β(1)b=-3.023 8,Cφb=-0.290 89,β(0)c=-0.293 04,β(1)c=2.155 6,Cφc=-0.004 256 0,θLi,Na=1.041 8,θB.C=-2.630 5,ψLi,Na,C=-0.063 91,ψLi,Na,B=0.493 56,ψLi,B,C=-0.478 42,ΨNa,B,c=0.306 16,In K(Li2CO 3)=-8.962 9,In K(Na2CO3@10H2O)=3.064 6,ln K(Li2B4O 7@3H2O)=-7.356 6,ln K(Na2B4O7@10H2O)=-7.477 8.以盐的溶解平衡常数为判据,运用Pitzer方程计算了四元体系Li+,Na+//CO2-3,B4O2-7-H2O 298 K时的溶解度,并采用等温溶解平衡法,对该体系298 K时溶解度进行了实验测定,同计算值相比,二者基本吻合.     

Metastable Equilibrium in Quaternary System Li2SO4 ＋ K2SO4＋Li2CO3 ＋ K2CO3 ＋ H2O at 288 K

IntroductionThe Zhabuye salt lake, Tibet in China, is famousfor the high concentrations of lithium, boron, andpotassium in the world. The main components areLi , K , Na , B4O72 -, CO32 -, Cl-, SO42 -, andH2O, including rare elements such as Rb and Cs .The…     

四元交互体系Cd2+, Na+//Cl-, SO42——H2O 298 K时的相平衡

采用等温溶解平衡法研究了四元交互体系Cd2+, Na+//Cl-, SO2-4-H2O在298 K的相平衡关系. 研究发现, 该平衡体系存在Na2CdCl4·3H2O复盐相区, 平衡相图中有七条单变度曲线, 三个共饱和点和五个结晶相区. 其平衡固相的结晶区分别为Na2SO4、CdSO4、CdCl2·2.5H2O、Na2CdCl4·3H2O和NaCl. 该四元交互体系平衡液相的物化性质随着Cd2+浓度的增加呈现有规律的变化. 研究结果表明, 镉盐在该体系中的溶解度大, 迁移性强, 增加了土壤环境污染风险.     

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.     

Measurements of the Solid–Liquid Equilibria in the Quaternary System NaCl–NaBr–Na2SO4–H2O at 323 K

Phase equilibria of the quaternary NaCl–NaBr–Na₂SO₄–H₂O system at 323 K were studied by the isothermal dissolution equilibrium method. The solubilities of salts and densities of saturated solutions were determined. Solid solutions [Na(Cl, Br)] were found in the experiments. The phase diagram of the quaternary system has no invariant point, but has one univariant curve at the boundary of Na(Cl, Br) and Na₂SO₄ crystallization fields. The experimental results show that an increase of the NaBr concentration is accompanied by an obvious increase of the solution density and the decrease of the solubilities of NaCl and Na₂SO₄.     

四元交互体系Li~ ,Na~ //CO_3~(2-),B_4O_7~(2-)-H_2O 298K相关系的理论预测及实验研究

采用三元体系的溶解度数据 ,运用多元线性回归法拟合了 Li2 CO3(a) ,Na2 CO3(b) ,Li2 B4O7(c)的单盐参数、溶解平衡常数及有关的混合离子作用参数 .它们的值分别为 :β(0 )a =-1 .2 3 5 5 ,β(1)a =-2 .65 46,Ca=-0 .0 0 4660 7,β(0 )b =-3 .0 3 0 6,β(1)b =-3 .0 2 3 8,Cb=-0 .2 90 89,β(0 )c =-0 .2 93 0 4,β(1)c =2 .1 5 5 6,Cc=-0 .0 0 42 5 60 ,θL i,Na=1 .0 41 8,θB,C=-2 .63 0 5 ,ΨL i,Na,C=-0 .0 63 91 ,ΨL i,Na,B=0 .493 5 6,ΨL i,B,C=-0 .47842 ,ΨNa,B,C=0 .3 0 61 6,ln K(Li2 CO3) =-8.962 9,ln K(Na2 CO3· 1 0 H2 O) =3 .0 64 6,ln K(Li2 B4O7·3 H2 O) =-7.3 5 66,ln K(Na2 B4O7· 1 0 H2 O) =-7.4778.以盐的溶解平衡常数为判据 ,运用 Pitzer方程计算了四元体系 Li ,Na //CO2 -3,B4O2 -7-H2 O 2 98K时的溶解度 ,并采用等温溶解平衡法 ,对该体系 2 98K时溶解度进行了实验测定 ,同计算值相比 ,二者基本吻合     

Measurement of Solid-liquid Equilibria in Quaternary System Li+, K+//SO42-, B4O72--H2O at 288 K

In order to utilize the brine resources in China, the solid-liquid equilibria in quaternary system Li⁺, K⁺//SO₄^2-, B₄O₇^2--H₂O at 288 K was studied by the isothermal solution equilibrium method. Solubilities and densities of solutions were determined experimentally. According to the experimental data, the equilibrium phase diagrams, density-composition diagram and corresponding water content diagram of the quaternary system were plotted. Double salt KLiSO₄ was found in the reciprocal quaternary system Li⁺, K⁺//SO₄^2-, B₄O₇^2--H₂O at 288 K. The quaternary system has three invariant points, seven univariant curves and five fields of crystallization. The five crystallization regions correspond to Li₂B₄O₇·3H₂O, Li₂SO₄·H₂O, K₂B₄O₇·4H₂O, K₂SO₄ and KLiSO₄, respectively. The crystallization field of salt Li₂B₄O₇·3H₂O is the largest, whereas that of Li₂SO₄·H₂O is the smallest. The experimental results show that Li₂SO₄·H₂O has a strong salting-out effect on other salts.     

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+//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。     

Li+，K+//CO32-，B4O72--H2O交互四元体系298 K介稳相平衡研究

我国西藏扎布耶盐湖卤水中蕴藏的锂、硼等资源是如此之丰富,实属世界罕见[1,2].     

Li＋, Na＋//SO42－, CO32－-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－, CO₃^2－-H₂O 288 K介稳相平衡及平衡液相的密度、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. 研究发现: 该体系介稳平衡中有复盐Na₃Li(SO₄)₂•6H₂O形成. 其介稳相图中有3个共饱点, 7条单变量曲线, 平衡固相为: Li₂SO₄•H₂O, Na₂SO₄, Na₃Li(SO₄)₂•6H₂O, Li₂CO₃, Na₂CO₃•10H₂O. 复盐Na₃Li(SO₄)₂•6H₂O和一水硫酸锂(Li₂SO₄•H₂O)的结晶区较小, 而Li₂CO₃的结晶区最大; 该四元体系介稳平衡条件下未发现Na₂SO₄•10H₂O的结晶区.     

Phase Equilibria of Quaternary System NaCl-NaBr-Na2B4O7-H2O at 348 K

The phase equilibria of quaternary system NaCl-NaBr-Na₂B₄O₇-H₂O at 348 K were studied by the isothermal equilibrium method. The solubilities and densities of the equilibrium solution were determined. According to the experimental data, the phase diagram, density-composition diagrams and water content diagram of the quaternary system at 348 K were plotted respectively. And the phase diagram consists of one univariant curve, two crystallization fields and without any invariant point of the quaternary system. The equilibrium solid phases of the two crysta- llization fields were Na(Cl, Br) and Na₂B₄O₇·5H₂O. The experimental results show that the quaternary system contained solid solution. The densities of the solution decrease with increasing NaCl concentration and increase with increasing NaBr concentration.     

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.