Studies On 308K Activity Coefficient Of Partially Containing Strontium Ternary Subsystems In Na⁺,K⁺,Sr²⁺//Cr,Br^--H₂O

Electrolyte solution is a common system in the fields of chemistry,geochemistry,environmental chemistry,etc.The Sichuan Basin is rich in underground brine resources.The brine is an electrolyte solution containing a large amount of ions.In order to exploit brine resources,it is necessary to study the multi-temperature phase equilibria and thermodynamic properties of the brine systems.The study of activity coefficients of thermodynamic properties is also an important basis for phase equilibrium theory research and production process.In this paper,the activity coefficients of related subsystems for strontium-rich in Sichuan underground brine are studied by using the electromotive force method.The activity coefficicents of four strontium containing ternary systems NaCI-SrCl2-H2O,KCl-SrCl2-H2O,NaBr-SrBr2-H2O and KBr-SrBr2-H2O at 308 K are determined.According to the reported Pitzer model,the average activity coefficient of the single salt of the 1-1 type electrolyte is calculated firstly,the electromotive force of single salt solution and mixed solution systems is measured respectively,and then the Pitzer mixed ion action parameter is fitted according to experimental data measured in this work and the linear regression method.Accordingly,the relevant thermodynamic parameters of mixed systems such as the osmotic coefficient coefficient 0,the water activity and the excess Gibbs GE are further calculated,which can provide basic thermodynamic data for the development and utilization of containing strontium underground brine.The electromotive force of the single solutions of NaCl-H2O,KCl-H2O,NaBr-H2O,and KBr-H2O are measured by electromotive force at 308 K.According to calculated single salt electrolyte activity coefficient,the electromotive force of electrolyte solution and the Nernst equation,the electrode response slope ? and the electrode constant E0 are regressed based on the experimental data.The relationship between the average activity coefficient of the single salt and the electromotive force is plotted.The experimental results show that the ion selective electrode has a good Nernst effect,and the experimental results are accurate and reliable.On this basis,the electromotive forces of four groups of mixed salt systems NaCl-SrCl2-H2O,KCl-SrCl2-H2O,NaBr-SrBr2-H2O and KBr-SrBr2-H2O are determined,and the average activity coefficients of each system are calculated based on the obtained electromotive force data.According to the experimental data and Nernst equation,the corresponding activity coefficients are calculated,and the relationship diagrams between the average activity coefficient of NaCl and KCl and the ionic strength score are plotted respectively It is found that the average activity coefficients of NaCl and KCl decrease with the increase of ionic strength.According to the Pitzer equation in the electrolyte solution,the Pitzer mixed ion action parameter in this work ?Na+,sr2+,?Na+,Cl-,Sr2+,?K+,Sr2+and?K+,Cl-,Sr2+ are obtained by using linear regression and Matlab program.The relationship diagrams between the average activity coefficient of NaBr and KBr and the ionic strength fraction are plotted respectively.The results shows that the average activity coefficient of NaBr in NaBr-SrSr2-H2O system decreased with the increase of ionic strength fraction;the average activity coefficient of KBr in KBr-SrBr2-H2O system increased with the increase of ionic strength.Based on the reported thermodynamic data,the unreported SrBr2 Pitzer single salt parameters at 308 K are fitted.Application of electrolyte solution Pitzer equation,the Pitzer mixed ion interaction parameter in this work ?Na+,Sr2+,?Na+,Br-,Sr2+,?K+,Sr2+ and ?K+,Br-,Sr2+ are also obtained by using Matlab program of linear regression.The calculated mixed ion interaction parameters are taken into the Pitzer equation,and the average activity coefficients of SrC12 in the ternary system of NaCl-SrCl2-H2O and KCl-SrCl2-H2O are calculated.The average activity coefficient of SrBr2 are calculated in the ternary systems of NaBr-SrBr2-H2O,KBr-SrBr2-H2O.The relationship between the average activity coefficient of SrCl2 and SrBr2 and the total ion intensity I is plotted.According to the fitting ion interaction parameters of Pitzer equations,the Pitzer equations are used to calculate the permeability coefficient ?,the water activity the excess Gibbs free energy GE of the above four ternary systems,and the relationship diagrams between the relevant thermodynamic parameters(GE,aw,?)and the total ionic strength are also plotted respectively.Finally,the research results are analyzed and discussed.