The Species Morphology And Equilibrium Of Boron In The Bittern Of The Magnesium Sulfate Subtype Salt Lake

Magnesium sulfate subtype salt lake brine has abundant inorganic salts,such as Mg²⁺,Li⁺,Cl^-,SO₄^2-,B of which there are more types of boron oxygen with anions,making the lithium extraction process and thermodynamic expression of salt lake more difficult.Therefore it is necessary to study the species morphology and balance regularity of boron in salt lake brine.In this paper,we use the easily hydrolyzed Mg（BO₂）₂ as a boron source,with the help of Raman spectroscopy and X-ray diffraction（XRD）monitoring methods,to research the species morphology and concentration changes of boron in boron-rich brine of Magnesium Sulfate Lake（Mg SO₄-H₂O,Mg SO₄-Mg Cl₂-H₂O）,Li Cl system（Li Cl-H₂O,Li Cl-Mg Cl₂-H₂O）,and boron-rich brine in Yiliping Salt Lake were studied and quantitatively expressed at 298.15 K.Chemical equilibrium and phase equilibrium law,the concentration quotient ln Q of the reaction equilibrium between boron species in the Three-way System of Mg SO₄-Mg Cl₂-H₂O and Li Cl-Mg Cl₂-H₂O was obtained in a linear relationship with the molar concentrations of[Mg SO₄,Mg Cl₂],[Li Cl,Mg Cl₂],respectively.This linear relationship model can extend the ln Q of boron species distribution in H3BO3-Na OH system to the multivariate system of{Mg SO₄,Mg Cl₂,Mg SO₄-Mg Cl₂},{Li Cl,Mg Cl₂,Li Cl-Mg Cl₂}aqueous solution,and provide a basis for estimating the species distribution of boron in water-salt system and then calculating the thermodynamic properties of boron-containing electrolyte solutions.The specific conclusions are as follows.Hydrolyzed solid phase characteristics of Mg（BO₂）₂:Mg（BO₂）₂ hydrolytic conversion to generate solid phases that are Mg B₂O（OH）₆,Mg B₄O₇·9H₂O and Mg（OH）₂ in Mg SO₄-H₂O solutions,Mg₂B₆O₁₁·15H₂O,Mg B₄O₇·9H₂O and Mg₂Cl（OH）₃·4H₂O in Li Cl-H₂O solutions,Mg₂B₆O₁₁·15H₂O,Mg B₄O₇·9H₂O and Mg₂Cl（OH）₃·4H₂O in Mg SO₄-Mg Cl₂-H₂O and Li Cl-Mg Cl₂-H₂O solutions.Hydrolyzed liquid phase Characteristics of Mg（BO₂）₂:（1）Hydrolyzed phase of Mg（BO₂）₂ in Mg SO₄ solutions has B₄O₅（OH）₄^2-,B₃O₃（OH）₅^2-,B₃O₃（OH）₄^-,B（OH）₄^-,H₃BO₃.With Mg SO₄ concentration from 0 to saturation,B₃O₃（OH）₄^-always accounts for more than 50.00%of the total boron in the liquid phases.Meanwhile B₃O₃（OH）₅^2-from4.77%of the total liquid phase boron rise to 37.16%;（2）In Mg SO₄-Mg Cl₂-H₂O solutions,the main morphologies of boron species are B₃O₃（OH）₄^-,B₃O₃（OH）₅^2-,B（OH）₄^-,etc.,in the co-saturation solution of Mg Cl₂ and Mg SO₄,the proportion of total boron in the liquid phase respectively is 58.91%,14.62%and 12.81%;（3）Hydrolyzed liquid phase of Mg（BO₂）₂ in the Li Cl solutions has B₅O₆（OH）₄^-,B₄O₅（OH）₄^2-,B₃O₃（OH）₅^2-,B₃O₃（OH）₄^-,B（OH）₄^-,H₃BO₃.And the main boron species in the liquid phase is B₃O₃（OH）₄^-,accounting for 39.65%～58.19%of the total boron in the liquid phase.We also noticed Li Cl solutions are conducive to the formation of boron ions with higher degree of polymerization.In research work,we found with the increase of Li Cl concentrations,B₅O₆（OH）₄^-accounting for the total boron in the liquid phase rose from 0to 17.50%when Li Cl is saturated,at the same time other boron species fluctuated in a small range;（4）The main boron species in the Li Cl-Mg Cl₂-H₂O system are B₃O₃（OH）₄^-,B₃O₃（OH）₅^2-,etc.,of which B₃O₃（OH）₄^-accounts for more than 23.92%of the total boron of the liquid phase.Simultaneously B₃O₃（OH）₅^2-accounts for more than 18.50%of the total boron in the liquid phase;（5）Mg SO₄ and Li Cl have a solubilizing effect on Mg（BO₂）₂.When the boron concentration is found to be high in the evaporation process of boron-rich brine,it is conducive to the formation of boron oxygen with high polymerization degree.And Li₂B₄O₇·3H₂O is precipitated in the late evaporation brine,and its purity is above 73.46%.Additionally the morphological changes of boron-rich brine systems are compared with boron species in Mg SO₄-H₂O,Li Cl-H₂O systems.Through this comparsion,we found the morphological changes of boron species in the evaporation process of boron-rich brine are consistent with those in Mg SO₄-H₂O and Li Cl-H₂O systems.