Thermodynamics And The Ion-interaction Of Borate Aqueous Solutions Containing Lithium And Calcium Ions

Borate minerlas havevery wide applications for their excellent performancein.Borates containingcalcium and lithiumare widely used as a chemical raw material in various fields of production and life,such as glass,flame retardant,steel,paint,ceramics and some other non-linear optical materials and excellent record materials.In this thesis,the synthesis,characterization,phase chemistry and thermochemistry of boratescontaining calcium and lithiumwere studied,which can be used to guide the utilization of oil/gas-filed brine rescource to meet the demand of borate market in China.In this thesis,high purity lithium tetraborate was obtained by recrystallization of lithium tetraborate as the raw material.High-purity minerals of CaB₂O₄·6H₂O,Ca₂B₆O₁₁·9H₂O and CaB₆O₁₀·5H₂O were successfully synthesized by controlling style of feeds,reaction time,temperature with the raw materials of sodium borate,calcium oxide,borax,calcium chloride dihydrate and secondary deionized water according to the literature and patents.The borate products were characterized by X-ray powder diffraction,TG-DSC and chemical analysis.The chemical and thermodynamic properties of the four borates were studied systemtimatically.The phase transformation experiments of Ca₂B₆O₁₁-H₂O and CaB60O10-H₂O at 323.15 K were carried out by isothermal dissolution equilibrium method.It was found that the calciumborates did not changeat 323.15 K for 30 days.The results of differential thermal calorimetry?DSC?showed that the calculated values of specific borate were in good agreement with the fitted values,and the specific heat increased with the increase of temperature.The precision densities of Li₂B₄O₇-H₂O,CaB₂O₄-H₂O,Ca₂B₆O₁₁-H₂O and CaB₆O₁₀-H₂O were determined by the U-type of MMA4500 high precision density method at temperatureranged from 283.15 K to 363.15 K.Moreover,the Pitzer single salt parameters of Li₂B₄O₇·3H₂O,CaB₂O₄·6H₂O,Ca₂B₆O₁₁·9H₂O and-CaB₆O₁₀·5H₂Owere fitted forthe first time on the basis of the Pizter ion-interaction theory of the electrolytes and the experimental results of the apparent molar volume data for the systems(Li₂B₄O₇-H₂O,CaB₂O₄-H₂O,Ca₂B₆O₁₁-H₂O,CaB₆O₁₀-H₂O)from 283.15 K to 363.15 K at 0.1 MPa.