Isothermal Evaporating Phase Equilibria in the Quaternary System （LiCl+NaCl+Li2SO4+Na2SO4+H2O） at 348.15 K and 0.1 MPa: An Experimental and Theoretical Study  

作　　者：GUO Ya-fei YUAN Fei LI Long WANG Shi-qiang DENG Tian-long 

机构地区：[1]College of Marine and Environmental Sciences, Tianjin University of Science and Technology, Tianjin, 300457, China [2]Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin, 300457, China

出　　处：《盐湖研究》2019年第2期69-77,共9页Journal of Salt Lake Research

基　　金：National Natural Science Foundation of China(U1607123,21773170 and U1707602);the Key Projects of Natural Science Foundation of Tianjin(18JCZDJC10040);the Yangtze Scholars and Innovative Research Team of the Chinese University(IRT_17R81)

摘　　要：The gradient solar pond technique is an economic separating process employed in the inorganic chemical industrial production of salt lake chemical engineering processes. In this paper, a novel isothermal evaporation experimental method was employed to simulate the evaporation phase equilibrium for the reciprocal quaternary system (LiCl+NaCl+Li2SO4+Na2SO 4+H2O) at 348.15 K to serve as a useful guide for lithium salt production via the depth solar ponds.The isothermal evaporation equilibrium solubilities and physicochemical properties,including the densities and pH values, were experimentally investigated. The dry-salt phase diagram,water-phase diagram, and the diagram of the physicochemical properties versus composition were plotted with respect to the experimental data. The dry-salt phase diagram consists of three invariant points,seven univariant solubility curves, and five crystallization regions, specifically halite(NaCl,Ha),thenardite (Na2SO4,Th),double salt (Li2SO4 · Na2SO4 , Db2), lithium sulfate monohydrate (Li2SO4 ·H2O, Ls), and lithium chloride monohydrate(LiCl·H2O, Lc). Based on Pitzer and its extended HMW model, the Pitzer single salt parameters, mixing ion interaction parameters, and thermodynamic stable equilibrium constants for the quaternary system at 348.15 K were obtained. The calculated phase diagram and experimental isothermal phase diagram at 348.15 K exhibited a great difference. Based on these results, the isothermal evaporation phase diagram can truly reflect the salt sedimentary in salt lakes and can be applied as a useful guide for the solar pond process.The gradient solar pond technique is an economic separating process employed in the inorganic chemical industrial production of salt lake chemical engineering processes. In this paper,a novel isothermal evaporation experimental method was employed to simulate the evaporation phase equilibrium for the reciprocal quaternary system（ LiCl + NaCl + Li2 SO4+ Na2 SO4+ H2 O） at 348. 15 K to serve as a useful guide for lithium salt production via the depth solar ponds. The isothermal evaporation equilibrium solubilities and physicochemical properties,including the densities and pH values,were experimentally investigated. The dry-salt phase diagram,water-phase diagram,and the diagram of the physicochemical properties versus composition were plotted with respect to the experimental data. The drysalt phase diagram consists of three invariant points,seven univariant solubility curves,and five crystallization regions,specifically halite（ NaCl,Ha）,thenardite（ Na2 SO4,Th）,double salt（ Li2 SO4·Na2 SO4,Db2）,lithium sulfate monohydrate（ Li2 SO4·H2 O,Ls）,and lithium chloride monohydrate（ LiCl·H2 O,Lc）. Based on Pitzer and its extended HMW model,the Pitzer single salt parameters,mixing ion interaction parameters,and thermodynamic stable equilibrium constants for the quaternary system at 348. 15 K were obtained. The calculated phase diagram and experimental isothermal phase diagram at 348. 15 K exhibited a great difference. Based on these results,the isothermal evaporation phase diagram can truly reflect the salt sedimentary in salt lakes and can be applied as a useful guide for the solar pond process.

关 键 词：Phase diagram Solubility LITHIUM chloride LITHIUM sulfate Pitzer model 

分 类 号：O642.42[理学—物理化学]