Study on Metastable in Equilibria System of Li～+, Na～+//CO3～（2-）, SO4～（2-）, B4O7～（2-）-H2O at 273K
|School||Chengdu University of Technology|
|Keywords||metastable equilibrium zhabuye salt lake lithium Pitzer model solubility|
An experimental study on metastable equilibria at 273 K in the quinary system Li+, Na+//CO32-, SO42-, B4O72- -H2O was done by isothermal evaporation method. The metastable equilibria for quaternary systems Li+, Na+//CO32-, SO42- -H2O, Li+, Na+//CO32-, B4O72- -H2O and Li+, Na+, K+//SO42- -H2O at 273 K were studied by isothermal evaporation method. Metastable equilibrium solubilities and densities of the solution were determined experimentally. According to the experimental data, the metastable equilibrium phase diagrams were plotted.The experimental results of the metastable equilibria show that the double salt 2Na2SO4·Na2CO3 and Na3Li（SO4）2·-6H2O form in the quinary system Li+, Na+//CO32-, SO42-, B4O72- -H2O at 273.15 K. In the metastable phase diagram, the quinary system has five invariant points, eleven univariant curves, seven fields of crystallization [Na2B4O7·10H2O and Na2CO3·10H2O, Na2B4O7·10H2O and Na2SO4·10H2O, Na2B4O7·10H2O and Li2CO3, Na2B4O7·10H2O and Li2SO4·H2O, Na2B4O7·10H2O and Li2B2O4·16H2O, Na2B4O7·10H2O and Na3Li（SO4）2·6H2O, Na2B4O7·10H2O and 2Na2SO4·Na2CO3].The metastable phase diagram of system Li+, Na+//CO32-, B4O72- -H2O is simple common saturation type. In the metastable phase diagram, the quaternary system has two invariant points, five univariant curves, four fields of crystallization The double salt Na3Li（SO4）2·6H2O and 2Na2SO4·Na2CO3 form in the quaternary system Li+, Na+//CO32-, SO42- -H2O at 273.15 K. In the metastable phase diagram, the quaternary system has four invariant points, nine univariant curves, six fields of crystallization. The experimental results of the metastable equilibria show that the double salt Li2SO4·K2SO4 and Na3Li（SO4）2·6H2O form in the quinary system Li+, Na+, K+//SO42- -H2O at 273.15 K. In the metastable phase diagam, the quaternary system has three invariant points, seven univariant curves, five fields of crystallization.According to the experimental solubility data of the quaternary systems Li+, Na+//CO32-, SO42- -H2O and Li+, Na+//CO32-, B4O72- -H2O, the Pitzer parameters caculated. As follow:β? =0.2034,β?=-0.2138, CLi2CO3φ=0.00041,β?=-2.075 CLi2SO4φ=0.0084,θLi,Na=0.0428,θCO3,B4O7=0.0573,θSO4,B4O7=0.12,ψLi,Na,CO3=0.63, ψLi,Na,SO4=0.004,ψLi,Na,B4O7=-0.0221,ψCO3,SO4,Li=-0.246,ψCO3,B4O7,Li=0.0326,ψCO3,B4O7,Na=-0.2894,ψSO4,B4O7,Li=-0.0572,ψSO4,B4O7,Na=-0.3021, and the solution equilibrium constant of Li2CO3, Li2SO4, Li2B4O7, Na2CO3, Na2SO4, Na2B4O7. On basis of equilibrium constant of deliquescence, the solubility values on metastable equilibria of the system Li+, Na+//CO32-, SO42-, B4O72- -H2O at 273K were caculated by Pitzer model. Relatively fit together with the experimental data.